5. An Opener.
Special tools, Punches, Wheels etc., are treated of at greater length in dealing with the different processes in which they are used.
CHOICE OF SKINS
The art of working in leather is now so general that it is not difficult to obtain skins specially prepared for the purpose. It is an essential qualification that nothing of a fatty nature be used in their preparation. The tanning process of the best skins, whether with a glossy surface artificially obtained by rolling or with a dull surface, should be a very simple one. Oak and sumach tannins (used especially for morocco leather) are those which best preserve the suppleness and capillarity of leather. The susceptibility of its colour to alteration from exposure
to light is greatly influenced by the materials used in tanning. Oak wood and chestnut are the tannins least influenced by light. Skins tanned with cassaigre and mimosa, light at first, become darkened in a marked degree by exposure.[1]
[1] See the observations on the importance of the tanning process in the preservation of leather, in the Note at the end of this volume.
So many varieties of leather are on the market that some guide will be found useful in selecting the most suitable for the different methods of decoration. These methods may be classified as follows:
Cut, or engraved leather. Carved leather. Punched or hammered leather. Modelled leather. Modelled leather with punched background. Leather decorated by pyrogravure and pointogravure. Stamped leather. Open-work leather. Leather mosaic.
The leathers which may be used in these various styles of decoration are
Sheep-skin. Cow-hide. Calf. Ox-hide. Morocco. Russia. Pig-skin. Chamois. Vellum.