Caring for Ivory and Bone - 1Earth Antiques and Appraisals Magazine

CARING FOR IVORY & BONE

Many cherished curios and pieces of jewellery are made of delicate bone or ivory, two materials which need careful treatment to keep them looking good.

Ivory and bone were particularly popular with the late Victorians and the Edwardians. These materials were often exquisitely painted and carved and were used for snuff and pill boxes, fans, combs, buttons, cutlery and jewellery.

Whether the piece you have is a junk shop bargain or a family treasure, it is important to know how to look after it.

Over-cleaning can cause as much damage to old, fragile objects as no cleaning at all. Incorrect cleaning may actually devalue antique objects, so always test any cleaning method on a small unseen area first before proceeding.

Care must also be taken where one cleaning method might affect another material (silver or mother-of-pearl inlay, for instance) which is part of the same object. Cleaning may also dislodge precious stones or other pieces held in place by the dirt.

BENEATH THE GRIME

You may find some surprises once the initial grime is removed (traces of old paint and gilding are typical on ivory and bone), but if you suspect the object is valuable, take a tip from today's museum experts and leave the traces rather than repainting.

Where objects are not valuable, repainting can obviously give a new lease of life. Always ensure that surfaces are clean before repainting or reglueing.

Natural materials respond best to pore ingredients. Spirit soap and micro-crystalline wax are used by museum experts to clean fragile old pieces. Avoid using modern cleaning products which are often too harsh for delicate patinas.

There are various kinds of ivory, ranging from elephant and walrus tusks to whale and hippopotamus teeth. Bone and ivory share similar properties but ivory has a greater proportion of hard tissue called dentine.

Real ivory can be identified by the striations (lines) which radiate from the centre, as in a tree trunk. Ivory and bone can be etched, painted, gilded and stained and are often used in inlay or veneers in cabinet work.

HANDLE WITH CARE

Old ivory can be very brittle, so handle it carefully. Be particularly wary if an ivory carving is shaded with a brownish grey; scrimshaw work and antique Japanese netsuke (sash cord buttons) are always finished like this, and cleaning it off would seriously detract from their value.

Ivory naturally yellows with age, so attempts to bleach it to a gleaming white are ill-advised. Bone also tends towards yellowness, becoming almost ochre in time.

Always begin with a mild cleaning method (one part spirit soap to twenty parts white spirit on delicate objects), and test this on an inconspicuous part of the item to see the effect.

Some experts suggest coating clean ivory with almond oil, but this can make surfaces sticky and eventually darken them. Polishing ivory with a completely colourless wax produces better results.

Bone and ivory were often used for paper knives and for necklaces, bracelets and other items of jewellery.

CLEANING AND POLISHING

This method of cleaning is suitable for ivory and bone. On particularly delicate items, use a milder solution of one part spirit soap to twenty parts white spirit.

Necklaces can be immersed for a few seconds, but do first check that the strings are strong or you may end up re-threading them.

REMOVING STAINS

Persistent stains can be treated with solution of citric acid. If this has no effect, use hydrogen peroxide dilute with 50 per cent water to lighten very yellowed and stained pieces of ivory and bone.

Where possible, immerse the item for two or three minutes: the effect of the treatment will not br fully apparent until the item dries out.

If stains remain after cleaning with spirit soap, apply a mild solution of citric acid with a brush, or soak object for a few minutes. Rinse and polish.

REPAIRING BREAKS

Non-valuable ivory and bone can be mended with a quick-bonding adhesive, as long as the surfaces of the break are clean.

Do not attempt to fill in cracks on antique ivory, as these may have been caused by extremes of temperature, and can close up again if conditions change.

A light-coloured beeswax will fill cracks temporarily until you can take the piece along to an expert who can advise on repair.

• Replacement bone and ivory for jewellery repairs can often be bought from specialist craft shops.
• A proprietary cleaner for tannin stained teeth is well worth trying on stubborn stains.
• With time, ivory and bone will lighten if left in sunlight. Piano keys, for instance, are less likely to go yellow if the lid is left open.
• To repaint ivory or bone, first clean the surface thoroughly, with a solution of spirit soap. Rinse the piece and allow It to dry naturally In sunlight for at least a day. Then apply enamel paints, starting with the background colour. Let each coat dry before adding another.