Recipe book produced by Robert Hamilton

1
Hints with respect to the Manufacture of Stone Ware.

The materials of which the body of stone ware is composed are Clay & Flint, the proportion of which varies in different works, according to the quality, with us it is one part of flint to four of clay by measure, but when more flint can be used it improves the ware but takes a greater heat to burn it.
The clay is the finest and purest that can be got, is quite free from iron, of which common clays are full, & burns [white] in the fire, having then the appearance of chalk.
The Flint is the common black, or gun flint, picked as carefully from calcerous

2 or other substances with which it is commonly mixed, is then calcined with a strong fire, when it becomes pure white and is then ground to powder with a water mill.
These minerals in the proportion mentioned are mixed together with water in a large tub, until they have the consistency of cream, then made to pass through a very fine silk [scard/scarch] or sieve in order to separate all the impurities and grosser particles, are then put upon a flat pan made of bricks, and the water boiled and evaporated from them until they regain the consistency of clay, which will easily work with the hands. The first thing therefore to be attended to is the materials used, what kind

3
Kind of clay – whether used as it comes from the earth or obliged to be exposed to the weather before it can be wrought – the operations made use of to purefy it -&c What kind of siliceous earth , whether common flint or whether quartz or crystals – the preparations made use of to reduce them into powder, if calcined, & how, in what proportions these are mixed together & the operations made use of to mix them perfectly.
Whether different kinds of clays are not mixed together for forming different kinds of ware – and what kinds of ware these clays make by themselves- through flint and clay may be intimately mixed together yet the one does not seem to act upon the other, or to dissolve one another – In

4
In spite of that there is however a kind of more intimate union takes place by their being kept long together and in a certain state of dampness, a sort of imperceptible fermentation is going on in the mass which produces a more intimate mixture with one another and this forming the body of the ware close and more compact. Observe therefore if you can the method of tasking the mixture of clay and flint, called slip from the pans, how it is laid up for use, & the manner of keeping it, the time it is kept before it is used etc.
Samples of the different kinds of clay used at the different works, and samples of the siliceous stones are to be endeavoured to be got.

5

2d After the materials are thus prepared the ware is either formed upon a throwing wheel, or moulded upon patterns made of gypsum from which they quit upon being dryed. They are then such of them at least as can be done turned and polished on a turning loom, those that cannot be put upon the loom are polished as well as they can be by the hand, and are then burned in kilns, constructed for the purpose, when they get the name of biscuit ware, being white without glaze and adhere to the tongue like a common tobacco pipe.
Before putting into the kiln they are placed in boxes (called seggars) made of fireclay, & kept from touching one another by little clay supports which they only

6 only touch in one point – Observe therefore the kind of seggars used, the construction and size of the kilns, the fuel used, the degree of heat& the length of time it is continued – Bits of the biscuit ware, which are to be got in plenty lying about the works are to be got so as to determine the quantity of the earths in it.
3d After the ware is made into biscuit it is nexed[sic] glazed, this is done by mixing 3 ior 4 parts of white lead with one of flint & a little clay with water until it be of the consistency of cream – the Biscuit ware being dipt into this, sucks it into its pores so that upon being taken out, it appears to be immediately dry. It is then placed in seggars and burnt

7
again in the kiln.
The same observations to be made here as at the former kilns and whether the seggars are glazed or not – The ware in coming from these kilns is then finished.
These are the common operations for stone ware, besides which however, there are many varieties – Sometimes before burning the ware is dipped into a mixture of a different coloured clay, or into a mixture of clay and some metallic calx, or other colouring matter which gives it a thin coat of that particular colour, this upon the turning loom is turned off in particular places so as to leave the original ground, thus forming bands or other figures on it. Sometimes there are little figures of a different kind or colour formed in moulds and applied

8 Applied to them, with many other vareties.
After the ware is finished as above mentioned if it is intended to be painted or enamelled – these colours which are all metallic calces or oxides ground into fine powder mixed with Borax, ashes, glass, or some other flux & an essential oil, commonly oil of turpentine, to make them work, are put on the ware with pencils after which they are burned again in a smaller kiln, called the enamel kiln – The Blues are all done by Zaffre or preparations of cobalt.

9

Of the Dresden Porcelain.

This Porcelain has all the qualities of the Indian and perhaps is even superior to it, in its grain which is more compact and brilliant.
It is exceedingly refractory, resisting the most violent heats without melting and sustaining the alterations of heat, and cold, without breaking.
The materials of which it is made, are first, that which the Chinese call petuntse, & the Germans Kisel which signifies flint & is nothing but white and vitriscible[?] quartz.
Second, that which the Chinese call kaolin, or porcelain earth by the Germans which is a pure white clay.
So these they add in different proportions

10

Gypsum, and fragments of Indian porcelain called by the Germans Schesbon, and by the French Jessons.
As the furnace in which it is burnt is so constructed as to have different degrees of heat in different places of it, so they make different compositions in order to sustain the heat of those different places – they have commonly three different compositions of which N.1, is intended to stand the greatest heat, & N. 3 the lowest.
The following are the proportions
N1 Pure clay….100
White Quartz…….9
Fragments of China ….7
Calcined gypsum… 4

N2 Pure clay ……100
White quartz ……….9

11

Fragments of china …8
Calcined gypsum….5
N3 Pure clay……100
White quartz….8
Fragments of china…9
Calcined gypsum….6

These materials must be chosen the purest that can be got, and freed from any heterogeneous matter and prepared as follows.
The clay by being well washed, and freed from every impurity.
The Quartz by being burned, ground to a fine powder and scarched{?screened}
The Fragments by being bruised in a stone mortar and then ground, and put through a fine scarch – and where the fragments are not to be got, the composition N3 is to be taken and formed into little cakes about the thickness of a crown, burned in the kiln and used instead of them.

12

The Gypsum must be reduced to powder, put in a copper vessell[sic] and calcined, until the whole water of its crystallization is gone, after which it is to be again ground and pressed through a fine scarch[?] the crystallized gypsum is the best, but where that cannot be got common alabaster may be used.
These materials are mixed together and called the Mass; of which the different pieces of the ware are formed.
But in order to produce the finest Porcelain, there must not only be the finest materials chosin, and pro-perly mixed together, but the materials must undergo a certain process, which constitutes the beauty of the Porcelain as without it the materials will never perfectly unite, and the Porcelain will come from the fire

13 rough grained and bloated.
This process which is kept a profound secret, consists in macerating the materials with a suitable menstruum in order to make a perfect combination of all its parts, is as follows.
The materials being all properly prepared as before directed, and the proportions weighed out and mixed together by pressing them several times through a hair scarch, they are then watered with rain water, & formed into a paste of a consistence sufficient to be wrought upon a wheel. It is then put into a ditch made in the earth, or into casks which are covered to keep out the dust, with covers of wood which do not fit exactly so that the air may have free access for the fermentation. After it has been some time there, the

14

Fermentation is perceived both by the smell, the colour and the touch; by the smell as it acquires the smell of Hepar sulpharis[?] – from the colour which from a white becomes a deep grey and by the touch by its becoming much more soft and pliable.
Great care must be taken that during the operation it is not allowed to dry, and this necessary humidity is given to it by watering it from time to time with rain water – and the older the Mass is the longer time it has stood it is always found to answer the better.
The German workmen generally prepare this Mass twice a year, which they do at the two equinoxes, as they think that at that time the rain water is more charged with the universal [furment?] & that the

15

fermentation goes on more quickly & compliably than at any other season of the year.. They likewise always preserve part of an old mass as a ferment for the new, nor do they ever make use of a mass which is not at least six months old.
It is this process which constitutes the great secret, and which they conceal most carefully. None but one person in a work knows it and he is sworn to secrecy. The place where the mass is fermented is kept always shut and no person ever allowed to enter it except the one who conducts the operation.
After preparing the paste, the glaze is to be formed with which the Porcelain is to be covered, this is called by the germans Glasau[?] & by the French couverte
The proportions of the materials of

16

Which it is composed differs in little manner as in the mass according to the heat it is meant to sustain in the furnace & is likewise commonly used of the following three different proportions.
N1 Quartz ….. 8
Fragments of china…..15
Calcined gypsum…9
N2 Quartz…..17
Fragments of china ….16
Calcined gypsum ….7
N3 Quartz ….11
Fragments of china…18
Calicned gypsum ….12
These materials are to be taken of the very purest kind and prepared in the same manner, as directed for the mass, then mixed with either distilled or filtered water &made

17
Of the consistency of cream in which the ware is dipped after it has been once burned. It is then burned again, first with a gentle fire of six hours, and then with an augmentation of the fire by degrees until it is as hot as the furnace can be made, which is continued until the core is sufficiently burned which is known by little proof pieces which are taken out from time to time
The feuel[sic] with which it is burned is always wood.

18.
Of the colours used for painting on Porcelain.

As the colours used are all metallic it is necessary to use certain fluxes in order to give them lustre and a proper adherence to the ware by facilitating their fusion
Calx of lead mixed with flint and borax has commonly been used in Germany & as some colours are more difficult of fusion than others they use them in different proportions.

For those colours which are difficult of fusion they use
N1 3 parts of Litharge
3 parts of white quartz calcined
2 parts of borax
These are powdered mixed together & put in a crucible the one half of which is left empty. A gradual heat is given at

19

First until the borax boils, and the fire is then increased until the whole is in fusion - when fluid it is poured out upon a stone which has been warmed – It is again repeated, & then reduced to very fine powder & put into a bottle well corked to keep it from the dust.
The flux for those colours which are easy of fusion is composed of
N2 4 parts of litharge
2 parts of calcined quartz
1 ½ parts of borax
Which are prepared in the same manner as the former
But these fluxes are subject to many inconveniences for the calx of the lead is easily reverified when it meets with any matter which contains Phlogiston, and this being afforded it by the oil with which the colours are mixed when

20 they are laid on blackens their colours and hurts their brightness, and therefore, for fine goods a flux made of glass, nitre and borax is preferable.
The glass used in this flux must be perfectly free from lead & ought to be ground in a stone mortar (not marble) and then pressed through a fine scarch. If it is processed in a metallic or marble mortar it must be well washed with nitric acid & then well cleaned from it by frequent washings. The nitre and borax must both be the purest that can be got & the latter must be calcined. They must then be mixed in the follwing proportions
N A Powder of glass …. 4 drachms
Calcined borax … 2 drachms 12 gns
Purefied Nitre 4 drachms 24 gns.

21

The nitre and borax are first mixed together in a glass mortar, and the powder of glass added & then beatierated [sic] together for an hour. The mixture is then left for 12 hours in a place free from dust, and afterwards put in a Hessian crucible of which it fills only one third part. It is then slowly heat’d being kept covered until the heat has risen pretty high when the cover is to be taken off. This operation which the glass makers call fritting is to purefy the composition from all combustible matter which it may contain and which might spoil the colour of the glass, & ought always to be carried on slowly and by degrees. The greatest care is also to be taken to have the crucible covered when ever new charcoal is brought near it, for fear that any small piece

22 should fall in which would infallibly spoil and destroy the colour of the glass.
When the crucible begins to turn red let it be close covered & surrounded with burning charcoal and kept in that state for two hours, during which the matter will boil considerably. When that is over & it settles to the bottom of the crucible stop the fire & when it is cold, the composition will be found of a dark deep red colour. – The crucible is then to be covered but not leeted (for fear any of the leating should melt and fall in among the composition) and placed in the hottest place of the porcelain furnace, and it is sometimes necessary to put one crucible within another for fear the glass should run through one of them.

23

When sufficiently burned there it is to be preserved free from dust, & it should not be ground to powder or sifted until it is to be used, as it is observed that it alters its qualities & that the colours which it is mixed with have not the same splendour nor are so beautiful as when the flux is fresh done, a phenomenon not easily accounted for.
The flux thus prepared is mixed with the colours and serves the same purpose in enamel & porcelain painting as oils or gums in other kinds of painting as it melts and mixes along with the colours serving to bind their particles together & to fix them on the surface of the white enamel or glaze of the porcelain, & to aid their vitrification. But as some of these substances vitrify much sooner than others, therefore each colour

24
Should have the quantity of flux which is necessary for its perfect vitrification.
If too much flux is used, the colour is drowned, spreads, and the outlines are not exact or well defined; and if too little is used the colour only attaches itself to the surface and not having acquired a sufficient degree of vitrification it remains tarnished and without lustre.
Great care must therefore be taken to determine by proper trials the quantity of flux necessary for every colour, not only with regard to its intensity but to its proper degree of fusibility. And no colours should be used which requires more than six times its weight of flux because then it does not run freely and cannot be applied with the pencil.

25

Of the colours used for Painting and porcelain.
Manner of preparing gold to be applied on porcelain
Take a dram of gold in leaves and put it on the fire in a crucible. Put an ounce of mercury into another crucible and heat it until it begins to smoke. When the gold is red, pour upon it the heated mercury stir the mixture well with an iron rod, and when it begins to smoke throw the whole quickly into a glazed vessel filled with water. When the amalgam is cold, pour off the water, and pass the amalgam through leather to separate the superfluous mercury; then put it into a china saucer and place it on a fire of charcoal to evaporate the mercury which will then leave the gold

---

26

In a fine powder.
Or take fine gold and beat it into very thin small pieces. Take a sufficient quantity of nitrous acid in a matrass[?] and put a small piece of the gold into it. Then add drop by drop muriatic acid until you perceive the two acids combined begin to act upon the gold, when you must put the MATRASS on a sam? Heat to digest in order to hasten the operation. Add more gold from time to time as it dissolves it, until it is perfectly saturated and will not dissolve any more. Dilute this solution with distilled water and add to it fixed alkali in liquor untill[sic] the whole is precipitated, and then wash the precipitate with boiling water until

27
it comes off tasteless. Then dry it in a silver china or glass vessel, and keep it in a bottle well corked from dust.
When you want to gild a piece of porcelain mix the powder with a little borax and gum water, and trace the lines with a pencil.
When dry bake it with a heat sufficient just slightly to melt the surface of the glaze of the porcelain. When it comes out of the furnace it is black, but its lustre is restored by rubbing it with fine Tripoli or emery: and it is afterwards to be burnished with a burnisher.
Gold can also be reduced to powder by grinding leaf gold, with about half its weight of sugar candy, and when the whole is reduced to powder grinding it with a muller until it is reduced to an impalpable

28

Powder then adding a sufficient quantity of warm water to dissolve the sugar when the gold falls to the bottom. Silver may also be treated in the same manner.

The method of preparing the other colours for painting on porcelain.

Purple.
Dissolve gold in aqua regia composed of equal parts of muriatic and nitrous acids and sal ammoniac.
Take two drams of pure tin, and dissolve it slowly in an aqua regia composed, one part muriatic to five parts nitrous acid, with three times its weight of water, and let the solution be fully saturated

29

Take half a dozen of cupelled silver reduced into grains and dissolve it in nitrous acid, mix it with the former solution of tin, filter them and keep the different solutions for use.
Take a long glass cylinder which will contain 10 or 12 ounces of water and fill it within two inches of the top. Stir this water with a tin rod, and during the stirring, pour in 10 or 12 drops of the solution of silver and tin mixed, & then add in the same manner 8 or 9 drops of the solution of gold. This mixture is first of a deep red colour which afterwards turns to a good purple. Continue this until you have finished all your solution, let the whole rest, and then pour off the clear water.

30

add more water, and decant it off in like manner until[sic] it comes off perfectly insipid after which dry it. It is then in a state ready to be employed by mixing it with a proper quantity of flux No 1 or A.
Violet.
Follow the same process but add more of the solution of silver and tin to the solution of gold, than in the preparation of the purple.
Brown.
This colour is used for objects which are intended to be covered with another principal colour, as the nerves and fibres of a leaf, which are afterwards covered with a green, which on being melted is transparent, leaving the bracts drawn by

31

The brown visible.
Take the solution of gold as before & add to it the solution of tin without the silver the water will then become black, then add common salt, & in the place of purple, you will have a deep colour bordering on the violet, which is the colour wanted. This colour is employed without any flux, because it is commonly intended to be covered with another. But if it is intended to be employed as the prevailing colour flux must be added to it as in the other colours.
Red.
Take scales of iron and dissolve them in aquafortis. Then precipitate them with a solution of salt of tartar. Pour off the liquor, & put the precipitate on a plate of iron & expose it under a muffle until it

32 acquires a fine red colour. which afterwards calcine with double its weight of purefied and decrepitated common salt, after grinding them well together in a glass mortar in order to incorporate them thoroughly with one another. The calcinations must begin with a gentle fire and be increased to the most violent it can bear without vitrefication for two hours. Let it cool, & grind it again, then pour warm water upon it & stir it well, decant off the water, and repeat this operation until the water is no more tinged.
All these different waters being put into a large glass vessel let them remain until the colour precipitates, then decant the clear water from the top, pour on more water and repeat this 4 or 5 times, then pour

33 the precipitate into a vessell[sic] and dry it.
All the red colours made from iron are exceedingly volatile in the fire which is a great inconvenience in enamel painting, but they become very fixed by calcining them with common salt. This appears to be owing to a small portion of the vitriolic acid remaining with them which reacting with the Phlogiston contained in the flux forms a sulphur which volatilises and carries off with it the metallic calx.

Another red
Take the best Hungarian vitriol, reduce it into powder and put it in a test under a muffle with a gentle fire continued for four days until the powder has acquired a fine red colour. A crucible may be employed

34 but great care must be taken that the matter be gaurded[sic] from the contact of the flame and the vapour of the charcoal.
This red powder is then to be put into distilled vinegar for three or four days, or even more, for the longer it remains the finer the red grows. It is then to be washed with distilled water, & the operation repeated but with a more moderate fire than the first time. And it is then treated with common salt in the same manner as directed in the former.

Black.
Take cobalt – calx of copper & umber equal quantities, reduce the whole into an impalpable powder & mix it with three parts of flux No 1 or with flux

35 marked A which is better.
Another Black.
Calx of copper four parts Smalt one parts and scales of iron one part, reduces into a powder and mixed as above.

Deep green.
Calx of copper or burnt copper, mixed with a little blue & Flux No 2.

Clear green.
Mountain blue mixed with flux No 2 calx of copper mixed with a little yellow & flux N 2
Another green.
Three parts of calcined copper, two parts of mountain green mixed and joined with flux N2

Yellow green
Two parts of mountain green, two parts of calx of copper, one part of smalt, all mixed with flux N2.

36

Blue
Smalt {bruised} with flux N 1 which colour mixes very well with the before mentioned green to form different shades.
Deep Blue
The deepest coloured smalt melted in a crucible and ground into an impalpable powder & then mixed with flux N2.
Soft yellow
White lead of Venice calcined in a crucible or in a test under a muffle & then mixed with flux N 2
Another
Naples yellow with a sufficient quantity of the same flux.
Method of making naples Yellow
Ceruss? 12 oz Diaphoretic antimony 2 oz Allum & sal ammoniac each half an ounce

37

Mix them well in a marble mortar & calcine them with a moderate fire for three hours taking care that the test is always kept red. The colour varies according to the quantity of sal ammoniac.

Orange
Four ounces of antimony, 2 ounces litharge, pulverise them and put the mixture into a crucible, which expose to the greatest heat of the furnace; then grind a second time the glass which is found in the bottom of the crucible & add three parts of flux n1. Put the whole into a new crucible and ? heat it & repeat the operation until it acquires a good colour. If a clear yellow is wanted add some of the former composition.

Brown
Take unber well washed, dried & calcined & mixed with a proper flux

38

Preparation of the colours.
Break them in an agate mortar with a pestle of the same, then add the oil, & grind the whole well together with a muller. Then add the flux in different proportions, which as well as the colours themselves should be exactly weighed in order always to preserve the same shade. The common proportion is 2 ½ parts of flux, to one part of colour, but some colours require less and some more.
As for example smalt only requires half its weight of flux.
The colours ought to be ground with a very small quantity of oil, for if too much is used, it leaves by its evaporation holes in the colour & the drawing is thereby rendered imperfect, besides that some

39 of the metallic calces are apt to be revived by the oil. After the colours are laid on they must be dried in a stove in order to evaporate the oil before they are burned.

The following are the processes which M de Montainy gives for the composition of enamel colours.
White.
Set a crucible in the fire and when it is red hot put into it one dram of pure tin. To this as soon as it is red add two drams of purefied and decrepitated common salt without removing it from the fire. Stir the mixture from time to time with an iron rod giving it a considerable heat. When the extremity of the iron rod begins to {???} it is a sign that the calcination is near

40

Finished, continue it afterwards for an hour after which take the crucible from the fire.
Grind this matter in a glass or china mortar & put it in a test made of the same matter with the Grey [beard?] to calcine. Increase the fire by degrees & continue the calcinations for three hours the matter will then be found to be hard and adhering a little to the test.
It must then be again ground to powder, & put into a large glass vessell[sic] and warm filtered water poured on it, until it swim[?] two or three inches above it; stir it well then pour off the water, & add more until the water is not tinged.
Allow all these waters to rest until the white colour is precipitated, then pour

41 off the clear water, and repeat the same until all the salts are washed away & the water comes off insipid. Commonly upon three drams of the matter to which half a pint or 8 ounces of water is added it will be sufficient to renew the water five or six times.
Put the white substance which now remains into a large earthen pot well glazed which will hold at least two pints of water, and fill it with distilled water which boil for two hours always adding more water as it evaporates. Then let it settle & pour off the water gently. Fill up the vessell[sic] again with distilled water which again pour off, then let the remainder stand for 24 hours when the rest of the water may be drawn off by a cotton wick.

42.
If the calcination has been strong enough, the powder will be of a greyish white, but if not it will be brown in which case it must be ground upon a glass & moistened with water for a long time, & roasted & boiled until it becomes white.
This powder dried so as not to be affected with dust, then ground upon a glass with three times its weight of flux gives a fine white.
The requisite for making it succeed are 1. that the tin be perfectly pure. 2. that no piece of charcoal fall into the crucible or test during the operation. 3. that the charcoal with which it is calcined be well lighted & do not smoke. 4 That the calcinations be long enough

43
And 5. That a sufficient quantity of water be used in bothe the washing and the boiling of it.

Purple.
Dissolve the finest gold in aqua regia, made of one part of sal ammoniac, and four parts of nitrous acid. Dissolve pure tin in aqua regia, made of five parts by weight of good nitrous acid with one part of muriatic acid, & and to it double or even triple its quantity of distilled water. The tin must be dissolved very slowly and separated from the black powder which is at the bottom.
The one of these solutions precipitated by the other produces a purple which varies according to the precautions used in making it.
Blue
The success of this depends entirely on the

44
Quality of the cobalt. In order to try which put a little piece without being calcined, into nitrous acid, weaken’d with two thirds of water, and the best gives the reddest colour. This red colour sometimes does not appear until after some days & to assist it, it ought to be put upon the fire. When it hath acquired the colour pour off the liquor so that what is at the bottom do not mix with it. Add to the remainder more nitrous acid,& water, & digest it as before.
Put these red tinctures into a china vessell[sic] & then add to six drams of the tincture 1 ½ drams of purefied common salt and stir it well. Let it rest for some time. Pour off the liquor & throw away what remains at the

45
bottom. Then heat it and after some hours of evaporation there will be a little precipitation from which also decant the liquor.
When the evaporation is carried so far that the liquor begins to thicken it will form green circles at the surface, which green colour will be communicated to the whole liquor in proportion as it thickens. It must then be stirred with a glass rod so that it do not stick to the vessel. It will then first turn to a red & afterwards to a blue. But if the cobalt is of the very best quality neither then green nor the red will appear, but it will turn at once blue, continue to stir it untill[sic] the whole appears under the form of a grained salt of a fine blue colour.

46
Nitrous vapours will then exhale in great quantity continue the evaporation until it becomes almost dry remove it from the fire whenever the vapours cease to exhale which operation will last about two hours. Let it cool and when cold expose it to the open air. It will then turn a little moist & have a slight reddish cast which will increase until it becomes a crimson.
Then put it upon the fire when it will regain its blue colour & more nitrous vapours will arise. It must be constantly stirred with a glass rod & kept in a small heat for about an hour & then exposed to the air again for some days. It will again attract moisture, & the red colour will again appear, But

47
Slower, and in less quantity. Continue these operations for a month or six weeks the nitrous vapours will diminish every time, until at last they will not be perceived & then it will neither attract moisture or acquire the crimson colour.
By these operations the colour is so fixed in the basis of the common salt, that it can support the washing with water which could not be the case if it was washed at first.
In order to try if it is right, take a little of it and put it into a glass vessel, pour water upon it to the height of three or four lines & let it stand half an hour. If the salt becomes red without communicating any colour to the water it is right, but if not, the former operation must be repeated. When it is right

48 pour water upon it until it covers it about an inch. A quarter of an hour after decant this water, & pour on fresh water. & continue this until the salt acquires a fine red colour from being blue before. Then dry it and place it upon a test in the fire until the red colour again changes into a blue.
This colour is then employed with three times its weight of flux & makes a most excellent blue.
If it is kept a long time it sometimes becomes red again, but the blue colour can be again restored to it by a new calcination
Yellow
Take three parts of lead which expose to the fire, when melted add to it one

49
Part of tin, which will be reduced upon the surface of the lead into a yellow powder which must be collected. Then calcine this powder, mix it with common salt & grind them together, then calcine it under a muffle and mix it with flux
Or
Take Naples Yellow & grind it with double its weight of common salt, and calcine it as before.

50
Furnace for white stone ware

These furnaces have commonly eight fire places & consequently eight c[himnies sic] in the inside which have no opening but at the top – All the top of the vault is filled with holes the first row has eight round the furnace just where it begins to taper, and which are placed between each chimney. Then 16 others above these & then 6 more round the hole in the middle of the furnace these holes from three to four inches diameter & are kept shut during the operation.
The seggars are placed so that there is a pile of them under each hole, & the uppermost seggar is covered with a cover in the form of a cone.

51
The ware requires only one burning, but it continues 48 hours. The time to give the glaze is about 4 or 5 hours before the end of the burning. At that time that is when it has burned about 43 or 44 hours they take eight bushels of salt. A workman mounts upon a scaffold and with an iron ladle[sic] throws it by the holes upon the cover of each side. As soon as the salt is thrown in the whole is stopped & thus they go round the furnace, continuing the same ioperation for four or six hours, without any other intermission than to allow the fumes of salt to subside.
The form of the cover of the uppermost seggar is such that the salt poured above it surrounds the whole pile. The muriatic acid is disengaged & gets into the

52
Seggars, strikes the surface of the ware, and vitrifies the flint thus constituting the glazing.

53

The composition of the Biscuitware at present used, is one part of flint to five of clay by measure.
The cream coloured glaze is 4 parts of white lead to one of flint
The Tortoise Shell glaze is made a little softer by the addition of 6/10 of a part of slip without flint.
The black glaze is
40 {.lb.} white lead
10{ lb…} flint
6 quarts of slip without flint
To 10 cupfuls of which take one cupful of manganese.

Green
3 cupfulls of copper
1 do Zaffre
120 do Tortoise Shell glaze
Yellow
12 parts tortoise shell glaze
1 part yellow Oker

54

Agate
8 parts slip
1 do powder blue
1 do manganese
3 do zaffre

Cane colour
1 part brown clay
4 “ white slip

French grey
1 part smalt
1 do white slip

Cream glaze
6 parts white lead
3 do flint glass
1 do slip
1 do ?tin ashes

Delft glaze
Take 100 lb Tin & 300 lb lead and calcine them together into ashes.
Take 200lb kelp & 600 lb fine sand mix them together & burn them below the delft kiln, & grind them

55

Then take 300 lb of the lead and tin ashes
450 lb of the above fritt
4 pecks salt
4 lb ? dust
6 lb smalt
Let these be very well mixed together & add 8 or 10 lb pot ashes
Then calcine it on a bed of sand under the kiln, after which it is to be ground to a fine powder made into a slip & the Biscuit dipt in it.

Yellow for Delft
22 lbs litharge
10 lb antimony
5 lb ?Tin ashes
¼ lb arsnic
Calcine them, grind them, & mix them with 3 lb more litharge & calcine them again.

---

56

Green
12 oz red lead fluxed with
4 oz flint
Then take 1 oz calcined brass to 16 oz of the above and melt Them together
Fine flux
½ lb litharge
1 ¾ lb pot ashes
2 ½ lb sand

Black glaze with lead ore
14 lb flint
7 lb brown clay
3 lb manganese
56 lb lead ore

Black glaze with red lead
18 b flint
7 lb brown clay
4 lb manganese
56 lb red lead

Brown glaze with lead ore
11lb flint
7 lb white clay
56 lb lead ore

57

Brown glaze with red lead
15lb flint
7 lb white clay
56 lb red lead

4lb flint
21 lb lead ashes
5 lb red lead
2 Scots pints white slip

5 lb flint
3 lb white sand
2 lb manganese
6 lb red lead
21 lb ashes
2 Scots pints brown slip

58
Colours for stone ware

Rose colour
1 grain gold
4 grains black tin dissolved in aqua regia
1 ounce Borax
½ “ white glass

Blue
3 parts borax
1 “ Smalt
2 “ white glass
& a little zaffre

Yellow
1 part antimony
A little rust of iron
3 “ borax
1 “ white glass

Green
1 part calcined copper
6 parts white lead
4 parts borax calcined together

59
Green
1 part blue verditer
3 parts flint glass
2 parts white lead
1 part borax & a little flint

Red
1 part copperas calcined until it becomes a bright red
3 parts calcined borax
Add a little antimony and white lead

Black
½ oz iron rust
¼ zaffre
¼ manganese
Calcine them together & add ½ ox borax

Green
1 oz verditer
10 “ white lead
2 “ Flint
2 “ flake white

60
Yellow
1 oz Naples yellow
3 “ white lead
1 “ flake white
½ “ antimony
1 “ flint calcined together

Black
1 oz scales of iron
1 “ manganese
¼ “ zaffre
Flux them with borax or flake white

Blue
1 oz zaffre
1 “ flint glass
1 “ flake white

Gold size
3 penny worth Gum Sanc arach?
3 “ Gum Amber
2 “ shell lac
Beat them well together& put them with

61
3 English pints of linseed oil & boil them gently
Then take 2 pence worth of Gum mastic put it into 3 gills of O Turpentine & as soon as dissolved put them all together & strain them through a flannel cloth
Gold lacker
1 part spirit of wine
1 “ Turmeric
A little dragon’s blood
A little saffron & a little shell lac
Mix them all together & strain them through a flannel

P62 blank

63
Blue for printing &c
20 ounces Zaffre
13 “ Pot ashes
1 Tea Cup Full of charcoal
?Run down in a flinted crucible. The two latter acting as a flux on the Zaffre reduces it to a metallic state which is found in the crucible under the ?scoice.
These calxes of metal are calcined (after the Bismuth that adheres to then is separated over a common fire) This calx for printing is fluxed – ½ lb calx to ? flux as follows and for printing 18 of calx and 16 of flux

Flux for blue
4 lib Cornish stone in a state of powder
1 “ glass
6 oz common salt
Run down together in the Biscuit oven

Arnatto
8 own of the above blue
4 “ borax
5 “ potash
18 “ glass

64
Dark brown
1 Blue
2 Calcined Ochre

Or which is better
1 calcined ochre
1 blue fluxed

Yellow underglaze
1 lb sheet lead
¼ lib Black tin [bracketed together] calcined to ashes
Then
4 ounces of these ashes
1 “ of antimony
1 “ of litharge

Green for edging
1 calcined copper
4 red lead
3 flint
Ground together in a mill and put on the ware after it is dipped in the glaze

65
This green edged ware must be fired in the bottom of the oven – old copper is the best and must be calcined on an old mould in the glass oven

A China Body
80 lib raw Cornish Stone
60 “ Calcined bones
20 “ flint
60 “ Blue Clay
Ground together at a mill then 1 Lib arnatto? to be added for staining
The bones to be calcined in the bottom of the Biscuit oven
Glaze for the above
20 Lib raw stone
10 “ Borax
5 “ Flint
Ground together then 30 lib of this fritt is to be added to 20 lib lead.

66

A brown under the glaze
Antimony, litharge and Borax
8 ounces each
½ “ calx of cobalt
Calcined in the {deleted} top of the seggars in the Biscuit oven under the chimney

Yellow under the glaze
4 ounces antimony
4 “ litharge
2 “ Tin ashes
Calcined the same as the above

Green under the glaze
4 ounces of the above yellow
1 “ of smalts
½ “ of calcined copper
Calcined as the other two

Orange under the glaze
16 ounces litharge
8 “ antimony
5 Crocus Macertus(?)
Calcined as the others
The above colours are very good of their kind.

67

Fluxes No 1
3 ounces – ?borax?lead
1 “ – run down together

No2
8 ounces Glass
2 Borax
2 red lead
Run down together

No3
2 lib glass
6” borax
2 ounces flint
Run down together

Rose colour for printing
16 grains of gold dissolved in A regia
2 “ lead
1 “ Tin ashes
Fluxed with 3 ounces of No 2

68

Olive green for printing
2 calcined copperas
1 Blue
Or
2 calcined umber
2 iron scales
1 blue
Run down together

Brown for printing
1 ½ blue
1 Ochre
1 manganese

Or which is better
1 Egyptian black clay
1 copperas
1 blue

Red for printing
2 calcined copperas
¼ flint
½ red lead

Black for printing
2 umber calcined to 3 of flux in

69

3 red lead
1 borax
1 flint
Run down together


Black under glaze
3 Ochre
1 manganese
1 Blue
Run down together

Enamel Blue
2 {ounce} crown glass
2 White enamel
11/2 Borax
3 drams blue
Run together

Enamel green
12 red lead
4 flint
1 calcined copper
1 enamel

Enamel red
3 calcined copperas to 1 Flux No 1.

70
Purple
8 glass
2 red lead
2 Borax
2 lead and tin ashes
Rundown then add 16 grains dissolved gold

Hair colour
1 iron scales
9 Flux – viz 15 R lead 5 flint calcined together

Yellow
3 red lead 1 tin ash
2 tin ashes or 1 flint
2 Antimony 1 lead

Rose colour flux
1 lib Flint glass
5 ounces red lead
Run together
1 dram dissolved gold
8 ounces leaf [solaris] mix together

71

Brown
3 calcined umber
1 Do Ochre
Fluxed with No 1

Shining Black
1 calcined Umber
4 borax
Ground together

Enamel Blue
2 ounces of calx of cobalt
2 “ of Borax
1 “ of nitre
16 “ of flint glass
Calcined in the glass oven

73
Pearl or Stone ware
Fired in the China Oven
3 bale clay
3 cornish stone
1 cornish clay

---

75

Primary Colours

“Cling round the aerial bow with prisms bright,
And pleased untwist the armful throws of light”

Sir Isaac Newton discovered that the prismatic spectrum was composed of seven colours in the following proportion, violet 80, indigo 40, blue 60, green 60, yellow 48 orange 27, red 45, If all these colours be painted on a circular card in the proportions above mentioned and the card be rapidly whirled on its centre, they produce in the eye the sensation of white. And any one of these colours may be imitated by painting a card with the two colours which are contiguous to it in the same proportions as in the spectrum, and whirling them in the same manner – Mr Galton of Birmingham ascertained in this manner by an act of experiment the following propositions.
1. Any colour in the prismatic spectrum may be imitated by a mixture of the two colours contiguous to it.

76

2d. If any three successive colours in the prismatic spectrum be mixed, they comprise only the middlemost colour.
3d. If any four successive colours in the prismatic spectrum are mixed, a tint similar to a mixture of the second and third colour will be reproduced.
4th. If beginning with any colour in the circular spectrum, you take of the second colour a quantity equal to the first, second and third, and add to that the fifth colour, equal in quantity to the 4th, 5th and 6th and with these combine the seventh colour in the proportion it exists in the spectrum, white will be produced. Because the 1st, 2nd and 3rd compose only the 2nd, and the 4th 5th and 6th compose only the fifth, therefore if the seventh be added, the same effect is produced as if all the seven were employed.
5th. Beginning with any colour in the circular spectrum if you take a tint composed of a

77

certain proportion of the 2nd and 3rd (equal in quantity to the 1st, 2nd, 3rd, & 4th) and add to this the 6th colour equal in quantity to the 5th, 6th & 7th white will be produced.

From these curious experiments many phenomena in the chemical changes of colour may probably become better understood, especially if the same theory must apply to transmitted colours as to reflected ones. Thus it is well known that if the glass of manganese, which is a tint probably composed of violet and indigo, be mixed in a certain proportion with the glass of lead, which is yellow, that the mixture becomes transparent. Now from Mr Galton’s experiments it appears that in reflected colours such a mixture would produce white, that is the same as if all the colours are reflected. And therefore in transmitted colours the same circumstances must produce transparency, that is the same as if all the colours were transmitted. For the particles, which constitute

78 the glass of manganese will transmit red, violet, indigo and blue; and that of the glass of lead will transmit orange, yellow and green; hence all the primary colours by a mixture of these glasses become transmitted, that is the glass becomes transparent.
Five successive prismatic colours may be combined to produce but one colour. For if you begin at any part of the circular spectrum, and take the 1st, 2nd, & 3rd in the proportion in which they exist in the spectrum, these would compose only the 2nd colour equal in quantity to the 1st, 2nd & 3rd; add to these the 3rd, 4th and 5th in the proportion they exist in the spectrum and this will produce the 4th colour equal in quantity to the 3rd, 4th & 5th. Consequently this is the same thing as mixing the 2nd and 4th colours only, which mixture would only produce the 3rd colour. Therefore if you combine the 1st, 2nd 4th and 5th in the proportions in which they exist in the spectrum with double the quantity of the 3rd colour this third will be produced.

79

Steam engine

“Quick moves the balanced beam, of giant birth
Wields his large limbs, and nodding shakes the earth”.
Captain Savory appears to have been the first who reduced the steam engine to practice and exhibited it in a useful form, his method for which he got a patent in 1698. consisted only in expelling air from a vessel by steam and condensing the steam by an injection of cold water which making a vacuum, the pressure of the atmosphere forced the water to ascend into the steam vessel through a pipe of 24 to 26 feet high, and by the admission of dense steam from the boiler, forcing the water in the steam vessel to ascend to the height desired. This construction was defective because it required very strong vessels to resist the force of the steam, and because an enormous quantity of steam was condensed by coming in contact with the cold water in the steam vessel.

80

Soon after that time M Papin attempted a steam engine on similar principles but rather more defective in its construction. The next improvement was made very soon afterwards by Messrs Newcomen and Charley of Dartmouth; it consisted in employing for the steam vessel a hollow cylinder, shut at bottom and open at top, furnished with a piston sliding easily up and down in it and made tight by oakum or hemp, and covered with water. This piston is suspended by chains from one end of a beam, moveable upon an axis in the middle of its length, to the other end of this beam are suspended two pump-roads[sic] The danger of bursting the vessel was avoided in this machine ,as however high the water was to be raised it was not necessary to increase the density of the steam but only to enlarge the diameter of the cylinder. Another advantage was, that the cylinder[…] not

81 being made so cold as in Savory’s method, much less steam was lost in filling it after each condensation.
The machine however still remained imperfect for the cold water thrown into the cylinder acquired heat from the steam it condensed, and being in a vessel exhausted of air it produced steam itself, which in part resisted the action of the atmosphere on the piston. Were this remedied by throwing in more cold water, the destruction of steam in the next filling of the cylinder would be proportionally increased. It has therefore in practice been found advisable not to load these engines with columns of water weighing more then seven pounds for each square inch of the arm of the piston. The bulk of water when converted into steam remained unknown until Mr Watt in 1764 determined it to be about 1800 times more than rare water. It soon occurred to Mr Watt that a perfect engine would be that in which

82 no steam should be condensed in filling the cylinder, and in which the steam should be so perfectly cold as to produce nearly a perfect vacuum.
Mr Watt having ascertained the degree of heat in which water boiled in vacuo under progressive degrees of pressure, and instructed by Dr Black’s discovery of latent heat, having calculated the quantity of cold water necessary to condense certain quantities of steam so far as to produce the exhaustion required, he made a communication from the cylinder to a cold vessel previously exhausted of air and water, into which the steam rushed by its elasticity & became immediately condensed. He then adapted a cover to the cylinder and admitted steam above the piston to press it down instead of air, and instead of applying water he used grease or oil to fill the pores of the

83 oakum and to lubricate the cylinder. He next applied a pump to extract the injection[sic] water, the condensed steam, and the air, from the condensing vessel, every stroke of the engine. To prevent the cooling of the cylinder by the contact of the external air, he surrounded it with a case containing steam, which he again protected by a covering of matter which conducted heat slowly.
Mr Watt gained a patent for this engine in 1768 but the further prosecutions of his designs were delayed by other avocations till 1775 when in conjunction with Mr Boulton an act of parliament was obtained for the prolongation of their patent for 25 years. Since that time, they have drained many of the deep mines in Cornwall. One of these engines works a pump 18 inches diameter and upwards of 600 feet high at the rate of ten or twelve strokes of seven feet long each, in a minute,

84 and that with one fifth part of the coal which a common engine would have taken to do the same work, the power of this ingine may be easier comprehended by saying that it raised a weight equal to 8100 pounds 80 feet high in a minute which is equal to the combined action of 200 good horses. In Newcomen’s engine this would have required a cylinder of the enormous diameter of ten feet, but as in this engine of Mr Watt a vacuum is made alternately above and below the piston, the power exerted is double to what the same cylinder would otherwise produce, and is further augmented by an inequality in the length of the two ends of the lever.

86 Morasses.
“Gnomes! You [?} taught transcending dews to pass
Through time-fallen woods and root-{?} morass”
Where woods have repeatedly grown and perished morasses are in process of time produced, and by their long roots fill up the interstices till the whole becomes for many yards deep a mass of vegetation. Morasses in great length of time undergo a variety of changes, first by eluctrication, and afterwards by fermentation and the consequent heat.
1 by water perpetually oozing through them the most soluble parts are first washed away, as the essential salts these together with the salts from animal ?(e)xcrements are carried down the sea; where all of them seem to decompose each other except the marine salt. Hence the ashes of peat contain little or no vegetable alkali. The second thing which is always seen oozing from morasses is iron in solution, which produces chalybeate springs, from whence depositions of ochre and

86 a variety of iron ores. The third eluctrication seems to consist of vegetable acid which by means unknown appears to be converted into all other acids. 1st into marine and nitrous acids as mentioned above. 2nd into vitriolic acid which is found in some morasses so plentifully as to preserve the bodies of animals from putrefaction which have been buried in them and this acid carried away by rain and dew & meeting with calcereous earth produces gypsum or alabaster, with clay it produces [? In the gutter of the notebook] and deprived of its vital air produces sulph[…] 3rd fluor acid which being washed away and meeting with calcareous earth produces fluor or cubic spar. 4th the siliceous acid which seems to have been disseminated in great quantity either by solution in water, or in air, and appears to have produced the sand in the sea uniting with calcareous earth previously dissolved in that element from

87 which soon afterwards formed some of the gritstone rocks by means of a silicious or calcareous cement. By its union with the calcareous earth of the morass other strata of silicious sand have been produced and by the mixture of this with clay and lime arose the beds of marl. In other circumstances probably where less moisture has prevailed, morasses seem to have undergone a fermentation, as other vegetable matter – new hay for instance is liable to do from the great quantity of sugar it contains. From the great heat thus produced in the lower parts of immense beds of morass the phlogistic part, or oil, or asphaltum, becomes distilled, and rising into higher strata becomes again condensed forming coal beds of greater or less purity according to the greater or less quantity of inflammable matter at the same time the clay beds becomes purer or less so, as the pholgistic part is more or less completely exhaled from them Though coal

88 and clay are frequently produced in this manner, yet there is no doubt, but that they are likewise often produced by eluctriation, in situations on declivities the clay is washed away down into the valleys and the phlogistic part or coal is left behind.

Flint

“Transmute to glittering flints her chalky [?]
Or sink on Ocean’s bed in countless sands.”

As the nodules of flint found in chalk beds possess no marks of having been rounded by [abrasion] or solution I conclude that they have gained this form as well as their dark colour from the flesh of the shell fish from which they had their origin; but which have been so completely fused by heat or heat and water as to obliterate all vestiges of the shell. Some nodules in chalk beds consist of shells of echeni? filled up with chalk the {animal} having been dissolved away by putrescence

89 in water or eaten by other sea-insects; other shells of echini in which probably the animals body remained are converted into flint but still retain the form of the shell. Others I suppose being more completely fused, have become flint-coloured by the animal flesh, but without the exact form either of the shell of the animal or the flesh. This idea of the production of the nodules of flint in chalk beds is {?countenanced} from the iron which generally appears as these flints become decomposed by the air; which by uniting with the iron in their composition reduces it from a vitrescent state to that of calx and thus renders it visible. And secondly by their being no appearance in chalk beds by a string or pipe of silicious matter connecting one nodule with another, which must have happened if the silicious matter, or its acid,

90 had been injected from without according to the idea of Dr Hutton. And thirdly, because many of them have very dry cavities at their centre, which should not have happened had they been formed by the injection of a material from without. When shells or chalk are thus converted from calcerous to silicious matter by the flesh of the animal, the new flint being heavier than the shell or chalk occupies less space than the material it was produced from; this is the cause of frequent cavities within them, when the whole mass has not been completely fused and {?} together.

91
Clay
“Whence ductile clay in wide expansion spread,
Soft as the cygnet’s down, this snow-white bed”

The philosophers who have attended to the formation of the earth have acknowledged two great agents in producing the various changes which this globe has undergone, these are fire and water, and have generally agreed that the stratification of materials could only be produced from precipitations, which were previously mixed or dissolved in the sea; and that whatever effects were produced by fire were perfomed afterwards. There is however great difficulty in accounting for the universal stratification of the solid globe of the earth in this manner, since many of the materials which appear in strata could not have been suspended in water; as the nodules of flint, the extensive beds of shells, and lastly the strata of coal

92 clay, sand and iron ore, which in most cool countries lie from five to seven times alternately stratified over each other, and none of them are soluble in water. Add to this if a solution of them in water could be supposed, the cause of that solution must come before a precipitation could commence. The great morasses of lava, under the various [names?] of granite, porphery, {L}oadstone, rag, [?] moarsteni and slate, may have acquired the stratification which come of them appear to possess by their having been formed by successive eruptions of a fluid mass, which at different periods of ancient time arose from volcanic shafts and covered each other the surface of the interior mass of lava would cool and become solid before the superincumbent strata was poured over it; to the same cause may be ascribed these different compositions and textures, which

93 are scarcely the same in any two parts of the world. The stratification of the great masses of limestone, which were produced from sea shells, seem to have been formed by the different times at which the innumerable shells were produced and deposited, a colony of echini, or madrophors? Or cornua amononia? Lived and perished in one period of time; in another a new colony of either similar or different shells lived and died over the former ones, producing a stratum of more recent shells over a stratum of others which had begun to petrefy or to become marble; and thus from unknown depths to what are now the summits of mountains the limestone is disposed in strata of varying solidity and colour. These have afterwards undergone variety of changes by their solution and deposition from the water in which they were immersed, or from having been ex-

94 posed to great heat under great pressure according to the ingenious theory of Dr Hutton. In most of the coal countries of this island there are from five to seven beds of coal stratified with an equal number of beds though of much greater thickness, of clay and sandstone and occasionally iron ores. In what manner to account for the stratification of these materials seems to be a problem of great difficulty.
The higher and lower parts of ?minafora were necessarily produced at different periods of time and would thus originally be found in strata of different ages. Now if we suppose the lowermost stratum of a morass becomes ignited, like fermenting hay (after whatever could be carried away by solution in water was gone) what would happen? Certainly, the inflammable part , the oil, sulphur or bitumen would burn away and be evaporated in air; and the fixed parts

95 would be left as clay, lime, and iron; while some of the calcerous earth would join with the silicious acid and produce sand or with the argillaceous earth and produce marl. Thence after many centuries another bed would take fire, but with less degree of ignition and with a greater body of morass over it, the bitumen and sulphur would then rise and might become condensed under an impervious stratum, which might not be ignited, and there form coal of different purities according to its degree of fluidity, which would permit some of the clay to subside through it into the place from which it was sublimed. Some centuries afterwards another similar process might take place , and either thicken the coal-bed or produce a new clay-bed, or marl, or sand, or deposit iron upon it according to the concomitant circumstances above mentioned.

---

96 I do not mean to contend that a few masses of some material may not have been rolled together by currents; when the mountains were even more elevated than at present , and in consequence the rivers broader and more rapid and the storms of rain and wind greater both in quantity and force. Some gravel beds may have been thus washed from the mountains; and some white clay washed from morasses into valleys beneath them and some ochres of iron dissolved, and deposited again by water; and some calcereous deposition from water (as the bank formation on which stand the houses at Matlock [?] but these are of small extent or consequence compared to the primitive rocks of granite or porphory which form the nucleus of the earth, or to the immense strata of limestone which crust over the greatest part of this granite or porphory; or lastly to the very extensive beds of clay, marl, sandstone, coal,

97 and iron, which were probably for many millions of years the only parts of our continents and islands which were then elevated above the level of the sea, and which on that account became covered with vegetation, and thence acquired their later or superincumbent strata, which constitute what some have termed the new world. There is another source of clay, and that of the first kind, from decomposed granite, this is of a snowy white and mixed with particles of mica, of this kind is an earth from the country of Cherokees. Other kinds are from less pure layers; Mr Ferber asserts that the sulphurous streams from Mount Vesuvius convert the lava into clay.
“The lavas of the antient solfatara have been undoubtedly of a vitreous nature, and these appear at present argillaceous. Some fragments of this lava are but half or at one side changed into white clay, which other is viscid and ductile

98 or hard and stony. Clays by fire are deprived of this coherent quality, which cannot be restored to them by pulverization nor by {?hamactation}. But the sulphurous Solfatura streams restore it, as may be easily observed on the broken pots when they gather the sal ammoniac; though very well baked and burnt at Naples they are modified again by the acid {stream?} into a viscid clay which keeps the former fire burnt colour”. Travels in Italy.

99 Enamels

“[?] her huge dragons with metallic hues
With golden purples and cobaltic blues”

The fine bright purples or rose colours which we see on china cups are not produceable from any other material but gold.
In Europe the application of gold to these purposes appears to be of modern invention. Cassius’s discovery of the precipitate of gold by tin, and the use of that precipitate for colouring glass and enamels are now generally known, but though the precipitate will then be more successful in producing the ruby glass, or the colourless glass which becomes red by subsequent ignition , the tin probably contributed to prevent the gold from separating which it is very liable to do during the fusion; yet for enamels the precipitates made by alkaline salts answer equally well, and give a finer red, than colour produced by the tin precipitate being a blueish

100

Purple, but with the others a rose red . I am informed that some of our best artists prefer acorean? Fulminarus, mixing it before it has become dry, with the white composition or enamel flux; when once it is divided by the other matter, it is ground with great safety, and without the danger of explosion whether moist or dry. The colour is remarkably improved and brought forth by long grinding, which accordingly makes an essential circumstance in the process.
The precipitates of gold, and the colcothar, and other red preparations of iron are called [?] colours. The heat must be no greater than just sufficient to make the enamel run? Upon the piece[sic], for if greater the colours will be destroyed or changed to a different kind. When the vitreous matter has just become fluid it seems as if the coloured metallic calx remained barely intermixed with it

101 like a coloured powder of exquisite tenacity suspended in water; but by stronger fire the calx is dissolved and metallic colours are altered by solution in glass as well as in acids or alkalis. The Saxon mines have till very lately almost exclusively supplied the rest of Europe with cobalt, or rather with its preparations, zaffre and smalt, for the exportation of the ore itself is there a capital crime. Hungary, Spain and Sweden are now said to afford cobalt equal to the Saxon.
Calces of cobalt and of copper differ very materially from those above mentioned in their application for colouring enamels. In these the calx has previously acquired the intended colour, a colour which bears a red heat without injury, and all that remains is to fix it on the piece by a vitreous flux. But the blue colour of cobalt and the green of copper are produced by vitrefication, that is, by solution in the glass, and a strong fire is necessary for

102

Their perfection. These calces therefore, when mixed with the enamel flux are melted in a crucible and the deep coloured opake glaze thence resettling, is ground and used for enamel. One part of either of these calces is put to ten parts or more of the flux according to the depth of colour required. The heat of the enamel kiln is only a full red viz 6 degrees of Mr Wedgwood’s thermometer. The usual materials for flux are flint or flint-glass, with a due proportion of red lead, or borax, or both, and sometimes a little tin calx to give opacity – Kaolin (see p108) is the name given by the Chinese to their porcelain clay, and petuntse to the other ingredient in their China ware. Specimens of both these have been brought into England and found to agree in quality with some of our own materials. Kaolin is the same with the clay, and petuntse with

P103 the granite found in Cornwall. There are differences both in the Chinese petuntses and Cornish granites: all of them contain micaceous and quartz particles, in greater or less quantity along with Feltspar which last is the essential ingredient for the porcelain manufactory. The only injurious material commonly found in them is iron, which discolours the ware in proportion to its quantity and which our granites are more frequently tainted with than the Chinese. Very fine porcelain has been made from English materials but the nature of the manufacture renders the process prococious and the profit hazardous; for the semivitrification which constitutes porcelain is necessarily accompanied with a degree of softness or semifusion, so that the vessels are liable to have their forms altered in the kiln, or to run together with any accidental augmentation of the fire.

104

Granite.
The lowest stratum of the earth which human labour has arrived to is granite; and of this likewise consists the highest mountain in the world. It is known under variety of names according to some difference in its appearance or composition, but is now generally considered by philosophers as a species of lava; if it contains quartz feltspat and mica in distinct crystals it is called granite. If these parts of the composition be less distinct, or if only two of them be visible to the eye, it is termed porphory, trap, whinstone, moorstone, slate, and if it appears in a regular angular form it is called basalts.
These are all esteemed to have been volcanic productions that have undergone different degrees of heat; it is well known that in Papin’s digester water may be made red hot by confinement, and will then dissolve many bodies which otherwise can little or not

105 at all be acted upon by it. From hence it may be conceived that under immense pressure of superincumbent materials, and by great heat, these masses of lava may have undergone a kind of aqueous solution, without any tendency to vitrification, and might thence have a power of crystallization whence all the varieties above mentioned from the different proportion of the materials, or the different degrees of heat they may have undergone in this aqueous solution. And that the uniformity of the mixture of the original earths as of lime, argil, silex, magnesia and barites, which they contain was arising to their boiling together a longer or shorter time before their elevation into mountains. The seat of volcanos seems to be principally if not entirely, in these strata of granite

106 as many of them are situated on granite mountains,and throw up from time to time sheets of lava which run down over the preceding strata from the same origin; and in this they seem to differ from the heat which has separated the clay, coal, and sand in morasses, which would appear to have risen from a kind of fermentation, and thus to have pervaded the whole mass without any exp(?) of lava
……….
“The kaolin (or Cornish Clay) is called by the Cornish miners Growan clay, & the petuntse (or Cornish granite) growan- stone. The Wha-she of the Chinese is the English soap-rock; and the other kan is asserted to be gypsum “ Embassy to china

107
Dr Franklin was the first that discovered that lightning consisted of electric matter, his discoveries taught us to defend houses and ships from lightning, and also to understand, that people are always perfectly safe in a room during a thunderstorm if they keep themselves at three or four feet distance from the walls; for the matter of lightning in passing from the clouds to the earth, or from the earth to the clouds, runs through the walls of a house the bark of a tree or other elevated object; except there be some moister body as an animal in contact with them, or nearly so; and in that case the lightning leaves the wall or tree and passes through the animal; but as it can pass through metals with still greater facility, it will leave animal bodies to pass through metallic ones. There was

108 an idle dispute whether knobs or points were preferable on the top of conductors for the defence of houses. The design of these conductors is to permit the electric matter accumulated in the clouds to pass through them into the earth in a smaller continuous stream as the cloud approaches, before it comes to what is termed striking distance. Now as it is well known accumulated electricity will pass to points at a much greater distance than it will to knobs there can be no doubt of their preference; and it would seem that the finer the point the better as it would take off the lightning while it was still out a greater distance, and by that means preserve a greater proportion of the building.

109
Sympathetic inks from Zaffre
The sympathetic inks from zaffre dissolved in the marine and nitrous acids have this curious property, that being brought to the fire one of them becomes green and the other red; but what is more wonderful they again lose their colours (unless the heat has been too great) on their being again withdrawn from the fire. Fire-screens have been thus painted which in the cold have shown only the trunk and branches of a dead tree, and sandy hills, which on their approach to the fire have put forth green leaves and red flowers, and grass upon the mountains. The process of making these inks is very easy. Take zaffre and digest it in aqua regia, and the calx of cobalt will be dissolved; which solution must be diluted with a little common water to prevent it from making too strong an

110(wrongly numbered 101)

Impression on the paper; the colours when the paper is heated becomes of a fine green blue. If zaffre or regulus of cobalt be dissolved in like manner in spirit of nitre, or aqua fortis, a reddish colour is produced on exposing the paper to heat.

Central fires.

M De Mavian has endeavoured to show that the earth receives but a small portion of the heat it possesses from the sun’s rays, but is principally heated by fire within itself, without which though the sun was constantly to illuminate two thirds of the globe at once with a heat equal to that at the equator, it would soon become a mass of solid ice.
The opinion that the centre of the earth consists of a large mass of burning lava has been esp[oused?] by Boyle, Boorhaave

111 and many other philosophers. There are many arguments in support of this opinion 1st Because the power of the sun does not extend much beyond ten feet deep into the earth all below being both winter and summer 48 degrees which being much warmer than the mildest frost is supposed to be sustained by some internal distant fire. 2nd. Mr De Luc in going 1359 feet perpendicular into the mines of Hartz on the 5th July 1778 on a very fine day, found the air at the bottom warmer than at the top of the shaft. In the mines in Hungary which are 500 cubits deep, the heat becomes very troublesome when the miners get below 480 feet depth.
3d. The warm springs in many parts of the earth at great distance from any volcano seem to originate from the

112 Condensation of vapours arising from water which is boiled by subterraneous fires , and cooled again in their passage through a certain length of the colder soil; for the theory of chemical solution will not explain the equality of this heat at all seasons and through so many centuries. The arguments which tend to show that the warm springs of this country are produced from steam raised by deep subterraneous fires, and afterwards condensed between the strata of the mountain appear much more conclusive, than the idea of their being warmed by chemical combination near the surface of the earth: for 1st their heat has kept accurately the same perhaps for many centuries; which cannot be well explained, without supposing that they are first in a boiling state; for as the heat of body

113 water is 212 and that of the internal part of the earth 48, it is easy to understand, that the steam raised from boiling water, after being condensed in some mountain, and passing from thence through a certain space of the cold earth, must be cooled always to a given degree.
2 In the dry summer of 1780, when all other springs were either dry or much diminished those of Buxton and Matlock had suffered no diminution; which proves that the sources of these warm springs are at great depths below the surface of the earth. 3d if these waters were heated by the decomposition of pyrites, there would be some chalybeate taste or sulphurous small in them – another argument in support of central fires is the situation of volcanos which are always found

114 upon the summits of the highest mountains. For as these mountains have been lifted up, and lose several of their uppermost strata as they rise, the lowest strata of the earth yet known appears at the tops of the highest hills; and the beds of the volcanos upon these hills must in consequence belong to the lowest strata of the earth. The volcanos themselves appear to be spiracula or chimneys belonging to the great central fires. This probably owing to the escape of the elastic vapours from these spiracula though the modern earthquakes are of such small extent compared with those of remote antiquity.