Inside the Collection

James Watt’s chemistry

Portable copy press box. Wooden box with brass features
Collection: Powerhouse Museum

19 January 2011 is the 275th anniversary of James Watt’s birthday. Because this is the International Year of Chemistry, to mark his birthday let’s take a look at Watt’s work as a chemist rather than as an engineer.

The portable copy press in the photo (which was shot in our Boulton and Watt exhibition) was patented by Watt in 1780 and made by James Watt and Co. The device used pressure to transfer ink from the original document to a damp piece of paper. It was the first reliable copying machine, and the same principle was used until typewriters and carbon paper came into common use. Watt experimented with different papers, wetting agents and inks to perfect the method.

Watt invented the machine because he and his partner, Matthew Boulton, wanted to keep copies of letters to clients and to the wide circle of friends who shared their interest in science and engineering. Many of these letters still survive and are very useful for researchers.

Copies of letters were made on very thin paper, so that the mirror-image copy made by transferring ink could be read from the other side of the page. Watt later realised he could also make copies of his engineering drawings, but these had to be read in reverse because they were made on thick paper. Hand-written notes on both the original and copy were made after the copying process.

Watt made chemical contributions to other industries, including chlorine bleaching of textiles and the firing of ceramics. He worked with Thomas Beddoes on medical uses of different gases. He also carried out experiments that were more ‘philosophical’ in nature, what we would call pure rather than applied science. He studied heat and the nature of steam, corresponded with other chemists, carried out experiments with Joseph Priestley, and was among the first people to realise that water is a compound rather than an element. His thinking was steeped in phlogiston theory and he found it difficult to accept Lavoisier’s new chemistry, which dispensed with that concept.

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