by M. Springate
Ivory is very sensitive to heat and light, as well as to moisture. When examining ivory, beware of heat from lamps, photo lights, and even your hands, especially if the ivory is thin (i.e. a veneer, or piano key). Ivory must be kept away from direct sun, heat, external walls (because of the danger of moisture condensation), cold windows, and any other source of moisture (i.e. the basement, or attic). This extreme sensitivity of ivory to changing relative humidity should be taken into consideration when it is being transported -- i.e. sudden changes from a dry climate to a humid climate, or transportation by air where there are sudden temperature changes. Special arrangements can sometimes be made -- ask your courier.
If ivory is kept in an environment where the relative humidity is 70% plus, you can get mold and mildew damage, including black spots and etching of the surfaces.
Ivory yellows with age, and when kept in the dark (this is why the bottom of an ivory object is often darker than the surfaces exposed to light). Ivory will also turn yellow/orange when exposed to sulphur, and must therefore not be stored with keratin-based objects such as tortoiseshell (keratin contains sulphur). Also, watch out for sulpher in adhesives, building materials, rubber, paints, etc. An activated charcoal scavenger may be helpful (sew a small bag out of unbleached cotton. Fill with the activated charcoal sold for fish tank filters, and sew closed. The activated charcoal absorbs sulphur and other impurities).
For storage, ivory should be wrapped in acid-free tissue or cotton, and stored in a polyethylene bag (i.e. a Ziplock) or a closed container (i.e. Tupperware). If necessary, enclose an activated charcoal bag. By storing ivory in these closed containers, changes in relative humidity will be moderated. Make sure that any display or storage materials are colourfast! Ivory is porous, and easily picks up colour, salts, and oils (i.e. from our hands -- cotton gloves are recommended when handling ivory); metal corrosion can also stain ivory.
Note that ivory becomes more brittle with age, and should be handled with care.
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Megan Springate is the proprietor of Uniclectica Antiques and Collectibles Online, which offers antiques, collectibles and reference books, as well as free show listings. This article comes from the ongoing information series, "Caring for Your Antiques and Collectibles", written from the perspective of an artifact conservator. The series is located at the Uniclectica site, (http://www.interlog.com/~uniques/conserv.htm). Megan can be reached at uniques@interlog.com, and welcomes suggestions for future articles.