Leather, which is nothing more than treated animal skin, often becomes dry and stiff with age, and in more recent times air pollutants have contributed to deterioration. Just like our own skin, leather responds to the application of moisture and oils - although, unlike our own living skin, it certainly won't respond well to being slathered in cold cream or steamed in a sauna.
One suggestion I've seen on various websites is to apply Vaseline, generically known as
petroleum jelly. Stop! Don't even think about using it! What might be soothing to living skin is
disastrous when used on the no-longer-alive skin covering books. Not long ago I had a couple
come in with a "jellied" book - a Bible whose once supple leather cover had turned hard
as wood. Following the advice found on a website, they had coated it with petroleum jelly and let
it sit while it absorbed what it needed. And what it needed was precisely none at all! The result
was a sticky, gooey mess and a cover that was still as stiff as the proverbial board.
[EDITOR'S NOTE: Also avoid beeswax, coconut oil, olive oil, paraffin, and saddle soap. Viscosity of these products is quite high, penetration correspondingly low, and some may actually do more damage by sealing off pores in the leather and preventing necessary breathing.]
Undoing this well-intentioned treatment was arduous. Because the endpapers needed replacing anyway, I removed the text block from the cover so that the pages would not be damaged. Repeatedly wiping the cover with paper towels removed some excess goop, but improvement was minimal. Nor did it help to let it sit wrapped in paper towels overnight.
Desperate times call for desperate measures: Mixing a solution of mild soap and water and wiping the cover without getting it too wet was of marginal help, yet it seemed that the jelly was determined to remain. It took multiple applications of alcohol to finally rid the cover of the grease that oozed from within its depths like some science fiction monster.
Fortunately, there are products especially designed for book leather that have been used by
such institutions as the British Museum and the Library of Congress. For this particular Bible,
an application of an amber-colored liquid called Restoration Leather Conditioner made
it fairly supple again, so that the cover and its text block could be reunited,
although the application of petroleum jelly no doubt prevented the preparation
from penetrating the leather as well as it might have. Restoration Leather Conditioner may
be purchased at
Talas.
As noted in the Talas description, make sure that any leather conditioner you buy for restoration contains a food grade solvent without sulfur. To quote: "Many low grade petroleum solvents contain sulfur which can destroy stitching."
Red rot is the scourge of leather-bound books, usually those from the later part of the 19th century. The term refers to a condition in which leather has degraded into a reddish powder. Oil was once the treatment of choice. The belief was that it was the drying of the leather that caused this powdery deterioration, and thus moisturizing it with oil would reverse the process. What the oil advocates didn't know is that red rot is actually caused not by dryness but by a chemical deterioration of the leather - specifically, a breakdown of the sulfuric acid that is found in vegetable-tanned leather. Oil can't reverse this condition, and oil plus dry powder produces a nasty, oily paste.
Is there hope once the dreaded red rot has taken hold of a book? Despite many claims to the contrary, red rot can be treated. Of course, you should remember that if you have an extremely valuable book, one that could secure your financial future, you should consult a conservator and not attempt any restoration work yourself.
Cellugel is a product developed especially for books affected by red rot. Applied liberally with a lint-free cloth, it is absorbed by the leather and dries within minutes. It will not darken, discolor, or leave a film on leather surfaces, nor will it harm paper or other book materials with which it comes into contact.
Cellugel contains cellulose ethers that penetrate the surface of the leather and leave
behind a thin film which also provides some protection against dust and pollutants. A second
coat may be necessary for extremely thick or badly deteriorated volumes. If the top is kept
closed, the product shouldn't evaporate, but a little isopropanol alcohol may be used for
thinning if necessary. You can expect a 16 ounce jar to treat about 60 average books. Here are
two sources:
A warning: While not dangerous if inhaled, the smell is pungent, so use it with good ventilation. Once the rot is arrested, you can touch up the binding using a good quality leather dye.
There are varying opinions as to whether red rot is contagious to nearby leather, rather like the chemicals given off by certain fruits and vegetables that cause others in close proximity to rot. To be safe, you may want to quarantine books suffering from red rot until the condition can be arrested.
Below are a few other products you might want to try with your leather books. These are also
specialty products and can't be picked up at a local department or home improvement store,
nor have I found them at craft or specialty art stores. Unless you're in a big city, you're
most likely to find these products online. An excellent, reasonably priced source of archival
products is
Talas.
Leather Dressing. A light-yellow, semi-liquid cream that cleans, Leather Dressing restores shine and suppleness and generally revives the feel of quality leather. Leather dressing can be buffed to a satin finish. Don't apply it to a book that is crumbling or damaged. Since it's made with lanolin and neat's-foot oil, there's no harsh smell, and both of these natural products are also kind to your hands. Some generic leather dressings contain wax, which coats the leather and prevents it from breathing. Avoid. Talas's Leather Dressing is manufactured from a formula developed by the New York Public Library and tested by the U.S. Department of Agriculture. You can be sure that it's wax-free.
Leather Protector. A yellow liquid that neutralizes acids caused by airborne pollutants,
Leather Protector also replaces natural salts used in the tanning process but later may have washed away. In addition, it protects against molds and mildew. The Talas formula was developed by the British Museum. Again, no harsh smell here, so use it anywhere. Apply with a lint-free cloth or use an inexpensive foam brush.
SC6000. A thick, creamy blend of waxes, acrylic resin, and isopropyl alcohol, SC6000 was originally developed as a surface coating for commercial shoe leathers but has been used by bookbinders and book conservators on their leathers for some 30 years. It imparts a nice sheen to books that have been re-dyed or otherwise have lost their "new book" look. An eight-ounce jar will cost about $20, but one jar has lasted me well over a year and will probably be with me yet another. I use this product when reattaching leather boards to make the Japanese paper used in the repair resemble the leather.
IMPORTANT-
BEFORE USING ANY OF THESE PRODUCTS:
- Clean the surface of the binding thoroughly before application. Otherwise, surface dirt or dust
will almost inevitably be worked more deeply into the leather. Because of its ability to lift dirt
from surfaces,
Absorene is an effective (and safe) cleaning agent
- Test the product first in an inconspicuous place. Some books, especially those bound in light-colored leathers and white vellum, will have a tendency to darken.
- Give special attention to the moveable parts of the binding - that is, the joints and the heads and tails of backstrips. These areas will typically experience the most severe damage.
- A final caution: Leather products, no matter how good, are ultimately only as good as their user. Use sparingly. The application of excessive amounts or too-frequent applications may result in a tacky surface or penetration through the boards to the endpapers - and subsequent staining.
[EDITOR'S NOTE: BookThink acknowledges that the application of leather preservatives isn't a universally accepted protocol in the book industry. Some conservators, for example, favor leaving things as is, occasionally advancing the claim that topical products speed degradation. However, as noted in this article, there is significant and relatively long-standing precedence for their use - and there's little question that many of these products improve the appearance of leather bindings, sometimes dramatically. As cautioned above, if you have a special book, consult an expert before attempting anything.]
