Leather what is it made of

Shrinkage temperature is used as a measure of degradation of leather. It is the temperature at which leather shrinks under specified conditions. Shrinkage temperature can roughly be correlated to collagen denaturation, the breakdown of the higher structural levels of collagen. As the structurally supportive hydrogen bonds and tannin crosslinks break down, the collagen structure is disrupted and the shrinkage temperature decreases. There is a direct relationship between shrinkage temperature and degree of degradation.

The vast majority of bookbinding leather is vegetable tanned. The two main types of vegetable tannin are condensed and hydrolysable. Most historic leathers will be tanned with some combination of tannins. Both condensed and hydrolysable tannins are weakly acidic phenolic compounds, which have anti-oxidant ability depending on their structure.

The anti-oxidant capability of tannins is reduced upon exposure to strong oxidizing agents. As tannins themselves degrade, the acidity of their environment is increased, which can increase acid hydrolysis reactions of other components of the leather.

The crosslinks between tannin and collagen are broken, and the leather detans resulting in a decrease in shrinkage temperature decreases. Hydrolysable tannins are those that when hydrolyzed break down to sugars and phenolic compounds, primarily galllic and ellagic acid. They are known historically to be more resistant to deterioration. Hydrolysable tannins have more naturally occurring salts and non-tans, which are thought to have a shielding effect against acid hydrolysis.

Hydrolysable tannins also have a high degree of anti-oxidant ability, which protects them from oxidation. Condensed tannins primarily degrade into insoluble compounds that are colored from yellow-brown to red. These tans have a reputation for higher degrees of deterioration than hydrolysable tannins. Condensed tans have a lower antioxidant activity and are more susceptible to oxidative degradation. Sulfur dioxide is readily absorbed by leathers tanned with condensed tannins, leaving them more vulnerable to acid hydrolysis.

The bond between chromium tanning salts and collagen is much stronger than in vegetable tanned leathers. This results in a higher shrinkage temperature and leather that is more resistant to deterioration.

Chrome-tanned leathers do not absorb large amounts of sulfur dioxide and do not show signs of appreciable degradation in accelerated aging trials. The working properties of chrome-tanned skins are not ideal for bookbinding. These skins have a high concentration of alum and salts that are thought to be protective against deterioration. Alum-tawed skins do not take up significant concentrations of sulfur dioxide and have proven to be very resistant to degradation. Washington DC : Library of Congress.

Bowker, Roy C. Calnan, Christopher and Betty Haines. Leather: Its Composition and Changes with Time. The Leather Conservation Centre : London. Canadian Conservation Institute.

Ottowa : Canada. Clement, Richard W. Accessed January 16, Cunha, George M. Conservation of Library Materials. Metuchen, NJ : Scarecrow Press. DePhillips, Henry A. July Elliott, Roy Gordon Henry.

Florian, Mary-Lou E. Fogle, Sonja, et al. Fredericks, Maria and Ethel E. Hellman, moderators. Book and Paper Group Annual Frey, Ralph Wylie and I.

Frey, Ralph Wylie and F. Grattan, David W. Greathouse, Glenn A. Causes and Preventative Techniques. Guldbeck, Per Ernst. Gustavson, K. Haines, Betty M. Hannigan, Mary V, J. Naghski, and W. Innes, R. London : British Manufacturer's Research Association. Jackel, Karl. Kronick, Paul L. Differential Scanning Calorimetry of Complexes with Sulfates. Larsen, Rene. Larsen, Rene, Marie Best, and U.

Leather Conservation Center. The Fibre Structure of Leather. Leather Conservation Center : London. Leikin, Sergey, Donald C. Rau, and Vozken Adrian Parsegian. McCrady, Ellen. McCrady, Ellen, and Toby Raphael. Accessed January 6, McLaughlin, George D.

New York : Reinhold Publishing Corporation. Middleton, Bernard C. The Restoration of Leather Bindings. Chicago : American Library Association. Nandi, P. Grant, D. O'Flaherty, Fred, William T. Roddy, and Robert M. The Chemistry and Technology of Leather. New York : Reinhold. Owen, Grace and Sarah Reidell. Petherbridge, Guy. Perminova, Olga I. Plenderleith, Harold James. The Preservation of Leather Bookbindings London. London: British Museum. Raphael, Toby, and Ellen McCrady. Reed, Ronald.

Ancient Skins, Parchments and Leathers. Roberts, Matt and Don Etherington. Accessed January 21, Rogers, Jerome Stanley and C. William Beebe. Leather Bookbindings: How to Preserve Them. Washington D. Rulfs, Charles L. Sclawy, Adrian Conrad.

Oxford: Butterworth-Heinemann. Smith, Richard Daniel. University of Denver : Master's Paper. John, Kristen. John , Kristin. Storch, Paul. National Park Service. Tapia, Guillermo. Teper, Jennifer Hain and Melissa Straw. Fredericks, Maria.

Wallace, Everett Leland. Circular no. Wallace, Everett L. Waterer, John William. New York : Drake Publishers, Inc. Wessel, Carl J. Accessed January 20, Wingate, R. Log in. Navigation Main Page.

Community portal. Current events. Recent changes. Random page. Specialty Groups Architecture. Conservators in Private Practice.

Electronic Media. Photographic Materials. Research and Technical Studies. Wooden Artifacts. Preventive Care. Work Practices. Additional Topics. View source. Jump to: navigation , search. What links here. Related changes. Special pages. Printable version. This needs to be a very generous layer of salt as the salt is what stops it from decomposing.

If a hide is not salted, brined or frozen within a few hours of being removed, the decomposition process can begin and the hide may become useless and be wasted. The hides tend to be stored, salted and folded with the flesh sides touching and will remain salted until ready to be processed when it should be soaked in water to remove any dirt or other materials. If a hide has hair on it then it will need this removed, which is executed using a chemical solution that contains calcium oxide.

This may be called a lime bath too and the soaking can take one to two days. This process will also soften the hide. After all this bathing and soaking, the hide will be full of moisture so it will swell to be around 4mm thick and can be spliced into two layers. This is done so separate parts of the hide can be used for different types of leather product. The upper part of the leather split is saved for the highest quality leather products such as full grain leather.

This is due to the fact the upper layer has a much tighter fibre structure making it more durable. When treated correctly this layer makes for a stunning and supple leather. The bottom layer of the hide will be kept for cheaper leathers with less overall quality than the top layer. These tend to be used for top grain and split leathers and are most commonly used for shoes and bags.

I notice from the various articles I read I seem to become enlightened on a particular part of the process that might have been glossed over in others. In this one, the description of a Staker machine for preparing the leather for its final finishing through stretching the surface.

I found to be especially enlightening. About Our Values. Our Workshop. Gift Ideas Gifts for Him. Gifts for Her. Stocking Fillers. Gift Sets. Travel Bags.