The conservator recommendations for caring for leather books has changed in the 21st century.
The first thing to understand when considering leather care is that leather is made from the skin of animals the most common of which are calf, goat and sheep. Other, less well known leathers include pig, kangaroo and even fish. You may be familiar with all kinds of leather in your life such as shoe leather, upholstery leather and clothing leather, but book leather is different in some significant ways mostly having to do with how it is tanned and finished. If you want more specific information on how book leather is made go to Hewit’s newsletter called Skin Deep. The quality of the leather on a specific book depends on many factors. The way the leather was tanned may make it more or less supple. The decorative dyeing techniques will also make a difference as to how they hold up over time. Some decorative treatments may include a wash of acid to create what is known as the “tree-calf” effect.
Most of this information on what kind of leather your book is covered with is a bit of a distraction. The variations of animal and history of how the leather got to be how it is now only leads up to the significant question of what do we do for the leather now to preserve it? Actually more important than what kind of leather it is is whether or not it has a deep grain or a flat grain. Is the surface pebbly or smooth? You need to test any pebbly leathers with the products you choose to use because it can get stuck in the cracks and not come out with buffing.
More important than what kind of leather your book is covered in is to understand the condition of it. Pristine leather that is simply dull will respond really well to just the Hewit’s leather dressing. Hewit’s is not the typical leather dressing. Since the late 1960s it was determined through extensive testing by conservators that the old accepted formula of lanolin and neat’s foot oil did nothing to extend the longevity of leather and in fact added a danger to the text-block through overly generous applications of the oily substances. Hewit’s is the best of the new era of book care. It is a wax based product that helps seal the leather. The previous thought was to “feed” the leather but leather is not a living thing so it just soaked up the oils like a sponge. Books are different than shoes or saddles. Those things are out in the elements and are constantly rubbed and scraped. They are not expected to last forever. Treatments that are good for shoes and saddles are not good for delicate books. First look it over and see if the leather is intact.
UNDAMAGED LEATHER CARE
- Clean: Dry-clean with gentle eraser If needed. Microfiber cloths are also good for this. Gentle “scrub” with humidified cloth
- Color: Before coloring scuffed leather, apply Klucel-G aka Cellugel(brand) to keep it from absorbing too much moisture.
- Correct: Probably nothing needs to be aligned if the leather is undamaged.
- Paste: Carefully! Too much moisture and pressure can damage the leather. Probably use Glue rather than Paste if anything needs attaching.
- Protect: Hewit’s leather dressing which is an archival esther wax that looks like milk. Don’t use actual milk, hand lotion or any oil-based products. Test first. This may not work well on Goatskin.
DAMAGED LEATHER CARE
Note the change. I added Clean/Protect to the beginning.
- Clean/Protect: Don’t use regular methods. It will only make things worse. Moisture will turn it black and make it crispy. Possibly scrape off icky bits with the knife and then use Klucel-G to seal the area (possibly the whole cover). Undamaged leather can be cleaned with a white polymer eraser such as Staedtler Mars.
- Color: Only after Klucel-G application. Only on the damaged areas. Less is more.
- Correct: Line up the pages and text block as needed.
- Paste: Paste is frequently the wrong thing to use for repairing damaged leather because paste is too wet. Use Glue instead, as dry as possible.
- Protect: SC6000, which is a thick pasty archival wax, is good for sealing really rough areas. Hewit’s Leather Dressing which is an archival anionically stabilized emulsion of hard ester wax. This is good for undamaged leather. Test first always. Don’t use anything that is wet on damaged leather or suede.