The Care and Feeding of Leather

While maintaining your leathers may sound as simple as going to your local boot black, it’s not that cut and dry when it comes to maintaining leathers in an archival or museum setting or after the leathers have been retired. An important consideration is that, except in the case of book-bindings, the function of historic leathers, and museum objects in general, is often changed from that of the object’s original function. Flexibility no longer plays an important role.

As long ago as 1946, H. J. Plenderleith noted that the only advantage to be gained from application of a dressing was possible increased flexibility. An increase in fat content, however, will only affect the object’s flexibility when the inflexibility is not the result of irreversible deterioration in the collagen fiber.

New Problems Created
In practice, the dressing of leather is also a largely irreversible procedure because of the deep penetration of the foreign ingredients and the movement of soluble components within the leather. The dressing can also impede future conservation treatments such as resin impregnation.

One of the major problems with commercial dressings is that people apply them for their immediate results without awareness of their long-term effects. Instability of certain fats or oils, dressing additives, and solvents contained in dressings can be responsible for numerous undesirable and unexpected effects:

Oils and fats can:
· become increasingly acidic
· form unstable surface spews
· oxidize and stiffen
· discolor and stain
· wick into adjoining materials
· leave a sticky surface
· encourage biological deterioration

Wax additives can:
· block surface porosity
· discolor and collect dust
· change the surface appearance
· impede further treatment
· encourage biological deterioration

Dressing solvents can:
· wet and swell the leather
· dissolve/dislocate original components
· affect surface finishes

Conclusions
It is evident that the dressing of leather is a popular and well-established procedure, yet there is a fair amount of experimental and practical evidence that suggests it has little or no effect on leather’s rate of deterioration. The regular dressing of leather is hard to justify in terms of conservation principles since it has little or no preservative effect when applied in a customary uncalculated manner and there are so many potentially dangerous side effects. It is recommended that staff not apply leather dressings to their historical collections on a routine basis. However, in certain individual situations, it may be appropriate for dressings to be applied by staff under the direction of a conservator. Lubricant solutions will also continue to be used on a limited basis during conservation treatment in which the specific components and quantity can be carefully monitored by a conservator.

Source: National Park Service COG No 9/1 7/1/93

[See NPS Museum Handbook, Part I (Rev 9/90),
Appendix S, “Curatorial Care of Leather and
Skin Products, ”]