Great numbers of these bindings were produced both in England and the United States from about 1840, and the process was used for many of the illustrated "table books" of the 1860s, as well as for many large folios printed on very thick paper. The process afforded both openability and durability, or so for the latter it was believed at the time. Both characteristics depended to a large extent on the purity of the rubber solution, and the degree to which it remained flexible. That it did not remain very flexible has been demonstrated by the fact most caoutchouc bindings have fallen apart. Also called "guttapercha binding," although incorrectly because gutta percha, which is also obtained from tropical trees was tried and found to be unsuitable. (89 , 236 )