Stabilizing Wet Skin and Leather
Facts about skin and leather
Skin products may be: untanned; semi-tanned (oil tanned, smoke tanned, alum tawed); or fully tanned (vegetable or mineral tanned). Remember that some skin products (in particular natural history specimens and ethnographic objects) may have been treated with pesticides and it is necessary to wear appropriate PPE when handling them.
What to expect when skin products get wet
- Untanned products will shrink, stiffen, thicken, cockle and discolor. With prolonged soaking, untanned products will disintegrate or gelatinize. These include parchment, vellum and rawhide.
- Some semi-tanned products (e.g. alum tawed leather) are as unstable as untanned products. Others, such as oil-tanned and smoke-tanned leathers, fare better, but may stiffen and become discolored in water.
- Fully tanned leathers are resistant to deterioration when wetted, but may still stiffen and darken. These include vegetable tanned leathers (shoes, belts, horse trappings) and mineral tannages (mainly 20th century, mainly shoes).
Drying skin products
- Skin products (including parchment, vellum and study skins) can be freeze-stabilized if necessary. Avoid direct handling of wet study skins, which will be greatly weakened, as they are easily distorted; allow them to dry in their storage trays.
- Controlled air drying is preferred. If dealing with large quantities, such as NH study skin collections, consider desiccant air drying.
- Pad out shaped items such as shoes and bags to shape while damp.
- Alum tawed leather
- Most natural history specimens
- Oil/smoke tanned leather (somewhat lower priority)
- Vegetable tanned leathers
- Mineral tanned leathers