Slip of paper
- Watt, James
1 Slip of paper, writing on as follows: “No.. 5, ½ oz copper, to a pound of tin”; “No. 6, ½ oz copper, to a pound of tin, and 2 pound spelter”; “No. 7, 1 lb tin, ½ oz copper, 1 pound spelter”; “No. 8, 1 lb tin, ½ oz iron, 2 pound spelter”
This item is part of the contents of the workshop that Scottish engineer James Watt developed at his home, Heathfield, at Handsworth, Birmingham. Although Watt is best known for his work on the steam engine, his workshop contains a wide variety of objects from many different projects, from chemistry to sculpture-copying.
The description of the item was written by Edward Collins, the land agent responsible for Heathfield when the workshop was given to the Science Museum in 1924. Collins could not always identify what he was looking at, but always described what he saw clearly. This has allowed his descriptions to form the basis of subsequent research.
These appear to be recipies for an alloy similar to pewter, though with raher a high copper content. Pewter is commonly supposed to be largely lead, and often actually contains it, but the superior pewter “tin and temper” was said to be tin with a small addition (between 0.43 and 0.65%) of copper. There was always uncertainly because the pewterers supposed that the metal worked best if a quantity of old metal were added to the new. Watt might have been interested in such alloys for any of a number of reasons, but their use for making bearings for shafts, nuts for press-screws &c. were well known by Watt’s time. Possibly these were recipes for hard-solders.