Very fragile ivory artefacts should only be treated by conservators. Artefacts in reasonably good condition may be cleaned of surface dirt and grime if proper precautions are observed. Refer to a conservator for the treatment of stains caused by contact with corroded metals or coloured materials.
Before cleaning or any other treatment, examine the object carefully to identify the nature of the material, to determine the strength of the object and to note whether it has been patinated or decorated. If the material is fragile, support it on a padded block which can be moved without direct handling of the object itself.
Guidelines for examination include:
- using a binocular microscope if possible. This will help estimate the depth and extent of cracks and the amount of deterioration;
- using micro-tests to determine the material of any decoration and how it is applied, as well as to determine its condition and ability to undergo any proposed treatment;
- noting and recording the presence of cracks (extent and depth), accretions, stains, old repairs, and new or recent damage; and
- observing objects under a long wave UV light (320 – 400 nm). This is usually helpful in locating old repairs and some accretions.
Objects in good physical condition may need only gentle dusting with a soft brush.
If brushing is not sufficient to remove the dirt and grime then careful wet cleaning may be attempted. Great care is needed if wet cleaning techniques are used. Water is potentially very damaging to these materials and non-polar organic solvents, such as toluene, have been shown to affect the organic components of ivory (Matienzo and Snow 1986). Ivory, for instance, has even been damaged by the application of damp swabs. Consultation with a conservator is highly recommended.
Follow the guidelines below if wet cleaning is necessary:
- never immerse an ivory object in water and do not apply water to cracked or porous surfaces;
- test any solvents on an inconspicuous part of any painted or decorated surface before any cleaning is attempted;
- roll a cotton bud, moistened with solvent (see below) over the surface to remove dirt. Clean only a small area at a time;
- immediately dry the surface with another cotton bud or soft tissue; and
- if necessary, remove residual soap with a cotton bud moistened in distilled water. Dry the surface immediately.
Solvents which have been used to clean ivory include:
- a solution of water and alcohol or methylated spirits (50:50);
- water containing a non-ionic detergent (see the chapter Ceramics);
- white spirit;
- white spirit containing a soluble detergent (such as Vulpex B-30); and
- leather cleaner (see the chapter Leather).
Leather cleaner has been found to be very effective. This cleaner has appeal as it has a low water content and its combination of a non-polar solvent and a non-ionic detergent, allows a range of surface contaminants to be removed. Care must be taken when cleaning ivory materials which have been deliberately painted as these attempts at cleaning may damage the original work. Even more care is needed when dealing with thin films of ivory as these are particularly susceptible to water damage.
Repair and Consolidation
Although it is strongly recommended that repairs and consolidation are left in the hands of experienced conservators, those with good hand and practical skills may feel confident enough to attempt simple repairs. Consult a conservator before taking this step however.
Objects that are broken or cracked can be repaired using pigmented resins. Do not use epoxy-based resins however as they yellow with age and cannot be removed by dissolution. This latter property makes future removal and re-treatment difficult. A further disadvantage of epoxy-based adhesives is that the adhesive is stronger than bone and ivory. Should further breakage occur it is best that the repair fail rather than cause a new break adjacent to the previous repair. Never using cyanoacrylate superglues for repairs. These have very low viscosities and run everywhere. The go deep inside the structure, closing off pores and are impossible to remove. They will cause differential responses to relative humidity changes and are capable of carrying dirt deeper inside the object.
If the ivory is flaky, powdery or delaminating, it may require consolidation using a resin and solvent combination such as Paraloid B-72 in acetone. For better penetration, work of this type should be carried out by immersion in a vacuum chamber. Colloidal dispersions such as Primal WS 12, WS 24 and WS 50 also can be used. These have better ageing properties than emulsions and due to their smaller particle size and viscosity, are better able to penetrate the ivory matrix.