Some old books contain a wonderful surprise - if you know where to look! Because a fore-edge painting is hidden, someone who does not know what they are looking for will miss it completely. You need to take the pages and fan them out slightly, and if there is a fore-edge painting, it will appear.
When I first started my bookselling apprenticeship, it was one of the first things I was told to look out for. Stephen Foster, UK
To create a fore-edge painting, the pages of the book are fanned out and then held in a vice. The painting is then applied, using water colours. Once the painting is dry, the book can be released from the vice. If this was all, you would still be able to see the fore-edge painting on the edge of the book even though it was flat, so to conceal it, the edge of the book is hidden either by using gilt, or sometimes marbled. Now the fore-edge painting would be invisible, unless you fanned out the pages.
Simply painting the visible edge of the book is a very old idea, maybe a thousand years old. But hiding a fore-edge painting under gilt dates from the 17th century. William Edwards of Halifax, who were bookbinders and booksellers, created some of the best examples of this art, from around 1750. Such was the demand, they opened a shop in Pall Mall in London.
Fore-edge painting became quite widespread, and continued into the 19th and 20th centuries. It is possible to create two quite separate fore-edge paintings within a single book by first fanning the pages one way and creating the first painting; then when that has dried you can fan the pages the other way, and create a second, completely different, painting. Traditionally the fore-edge painting would be applied and then the gilt. But it is also possible to take a book that already has a gilt edge, and apply a fore-edge painting to it.