White ceramic jar with lid, containing white powder, labelled “Sachm. Saturni”, unsigned, United Kingdom, 1790-1819.
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.
This pot contains Saccharum saturni (lead acetate), used experimentally by Watt as a mordant in experiments with dyestuffs for use in textiles. Watt has been in correspondence with Gilbert Hamilton in 1775 about chemical issues associated with calico printing. This led Watt into an interest in the use of mordants in printing, for fixing the colours in the cloth and making them resistant to being washed out.