If you’ve ever used late 18th century or 19th century business records, you may well have come across ‘wet copy’ letter books. These distinctive volumes are made up of letters on very flimsy, thin paper, with rather blurred writing which appears in reverse – although because the paper is so thin, you can read the writing from the other side.
Wet copy letter books are definitely not one of my favourite kinds of record. Because the paper is so thin, you get hundreds of fragile blurry letters in each volume; I’m always impressed by the researchers who have the patience to go through them.
Despite their drawbacks, you have to admire the ingenuity of the invention, which was patented in 1780 by James Watt. There’s an excellent article by Dr Brian H. Davies about the invention of wet copies on the Ceredigion Archives blog, which explains how they were produced. There are also pictures of wet copy letters, so if you’ve never seen one before, do take a look – and be glad you don’t have to use them!