Preventive Conservation
Environment
Display and store items made from leather, hide and skin in a clean, well-ventilated environment maintained at a maximum temperature of 25 °C with a relative humidity in the 45 - 65 % range, with daily fluctuations limited to 4 °C and 5 % respectively.
Very dry conditions (less than 40 % relative humidity) will cause loss of moisture and embrittlement while high humidity (greater than 70 % relative humidity) encourages mould growth. Parchment is very sensitive to relative humidity fluctuations and changes dimensions as it absorbs and releases moisture into its surroundings.
Protecting skin products in a storage or display cabinet will help to stabilise environmental fluctuations while also providing protection against dust and insect attack.
As all light has the potential to damage leather, keep light levels to a minimum, particularly for dyed leather (see below for recommended levels). Avoid exposing any leather to bright spotlights or direct sunlight as both of these can cause discolouration, desiccation and embrittlement.
| Best light values for leather objects | ||
|---|---|---|
| Material | Total white light (lux) | Maximum UV (µWatts/m2) |
| Dyed leather | 50 | 1,500 |
| Undyed leather | 200 | 15,000 |
More information on aspects of preventive conservation is provided elsewhere (Raphael 1993, Kite and Thomson 2006).
Storage and Display
To maintain leather in good condition a high standard of cleanliness is needed. Vacuum and remove dust from storage areas regularly to minimise the likelihood of microbiological, insect or rodent attack.
Protect leather objects from dust (cupboards, unbleached calico or tyvek dust covers, acid-free boxes or acid-free tissue) and inspect them frequently, preferably every six months, to ensure mould or insect infestations are noted at an early stage. Use only unbuffered acid-free materials with leather because buffered acid-free materials are alkaline and are therefore potentially damaging to the slightly acidic leather.
Support leather objects in their desired shape when in storage and on display so that they do not need reshaping as they age and harden. Avoid sharp folds or creases in leather unless it is the original shape of the object. Fill rounded items with unbuffered, acid-free tissue paper. Supports of other shapes can be made from chemically stable polyethylene or polypropylene foams. To avoid stressing them, store large or long leather pieces horizontally.
If three-dimensional objects are unable to support their own weight, support them internally. The form of the support will depend on the shape of the object and the weight of leather to be supported. Fit leather clothing or large objects such as saddles on made-to-measure dummy mounts. Chemically stable materials, such as the above-mentioned foams, linen, dacron and most metals, may be used in the manufacture of these supports.
Use painted metal storage cupboards and furniture to reduce the risk of acidic vapours from wood products coming into contact with skin materials. If wooden furniture is used then seal and line it with impermeable coatings (for example, clear, water-based polyurethane) or laminates (see the chapter Preventive Conservation: Agents of Decay).
Standard conservation-quality mounting and framing is usually adequate to protect art or documents on parchment.