How to Care for...
Leather and Skin Objects
Introduction
Animal skin has been used since prehistoric times for a wide variety of things. It continues to be a very important raw material. In modern household collectibles, it will be found in a wide range of objects such as bookbindings, shoes, clothing, sports equipment, and furniture. Skin can be used without tanning in such forms as parchment and rawhide. Partially tanned skin includes many of the skin products prepared by Aboriginal peoples. These skins are very soft and flexible, but are sensitive to water and are prone to stiffening with age. Another process called alum tawing was used for gloves through the 19th century. Skin prepared in this way is very sensitive and should not be wetted at all. When skin is fully tanned by exposing it to chemical treatments, it becomes leather. This is a chemical process that is difficult to reverse. Some leathers are very durable while others disintegrate under certain conditions. Vegetable tanning, which uses barks rich in tannins, is the traditional method that has been used for millennia. Since the 19th century, mineral tanning using chromium and other metallic salts has become more popular. The leathers produced by this category of processes are extremely durable and water-resistant.
Cleaning
Cleaning objects made from skin products cannot be done safely without knowing what process has been used in their preparation. Sometimes the application can provide clues. Parchments, drum heads, and coverings of wooden boxes are made from raw skin that has had no tanning or other chemical treatment. Old items of Aboriginal clothing are likely to be semi-tanned (a process similar to fat liquoring, but not as effective) while newer items, regardless of source, are likely to be chrome tanned. Handbags, bookbindings, and other items that do not need high water resistance might be made from vegetable-tanned leathers. Items such as shoes and clothing tend to be made of leathers that are durable and water-resistant. If made in the 20th century, the leather is likely to be mineral tanned. The resistance of these items to water, and thus the potential for effective cleaning, follows the order indicated below:
- rawhide and parchment - most sensitive
- alum tawing
- semi-tanned skin
- vegetable-tanned leather
- mineral-tanned leather - least sensitive
Obviously, with the wide range of skin products, and the corresponding wide range of applications, it is dangerous to generalize. When in doubt, seek professional advice.
- For all semi-tanned skins and those that have soft, sueded
surfaces, use a soft brush and vacuum cleaner. Brush towards
the nozzle of the vacuum cleaner. Place a piece of gauze
window screening over sensitive areas and vacuum through
it. A stiffer brush, such as an artist's hog bristle, can
be used on resistant areas, but be very cautious because
this might change the surface appearance.
- Rawhides and parchments can be cleaned with the powdered
eraser used by draughtsmen or a gum eraser. These materials
should be applied very carefully because a vigorous application
can cause over-cleaning. If there is any writing, painting
or other design on the skin, do not clean. Get advice from
a conservator. Directions on cleaning rawhide can be
found in CCI Note 8/4.
- Vegetable-tanned leathers can be cleaned by damp swabbing. Make sure that the leather is in sound, stable condition. Any sign of cracking or a powdery surface should be a warning that deterioration is taking place. If the leather is in good condition, use a soft cloth moistened with water to which has been added a few drops of liquid detergent. Rub gently and dry afterwards with another soft cloth, thus making sure that moisture is not left on the surface. The same technique can be used for mineral-tanned leathers that are very resistant to water. Directions on cleaning leathers can be found in CCI Note 8/2.
It is very common to apply leather dressings of various kinds to keep objects soft and flexible while in use. These materials are not generally recommended for heirlooms or heritage objects because their conditions of use and handling are different. Leather objects that are used every day, such as saddlery and furniture coverings, do benefit from treatment, but objects that lie unused or stored away tend to get sticky and attract dust and insects. Professional advice should be sought before applying any such treatment.
Handling
Flexible leather objects in good overall condition can be handled without problems. If objects are not on display, it is advisable to keep them wrapped in acid-free tissue paper and stored in such a way that they are not creased or distorted. Shoes and bags should be stuffed lightly with acid-free tissue to help maintain their shape, and light garments should be hung on padded hangers. Heavy leather garments are best stored flat to avoid distortion due to gravity. Flat skin or leather pieces should be wrapped in tissue and kept in a flat, rigid binder or folder to prevent distortion. CCI Notes 13/2, 13/3 and 13/5 give advice about storing textiles, much of which is applicable to flat leather objects. Bookbindings are discussed in our section on books on this Web site.
Repair
Repair of historic leather and skin objects is usually needed when items are badly deteriorated. Before repair is done, deterioration needs to be dealt with. In most cases, such repairs are a job for the specialist. If in doubt, consult a conservator.
