Care and cleaning. To retain its warm-white color, ivory mustbe exposed to light. If you always keep ivory-handled knives in a chest or a piano’s ivory keys covered, they will eventually darken and yellow.
Dust ivory with a soft, clean cloth. Wash ivory in mild soap and water, rinse, and dry it. Buff it with a clean woolen cloth. Don’t soak pieces such as jewelry or knives; water can soften the glue that holds the ivory in place.
To clean ivory piano keys, pick up a small amount of baking soda with a slightly damp cloth and gently rub one key at a time. Wipe the keys clean with a damp cloth; buff them dry.
To whiten slightly yellowed ivory, try rubbing it with lemon juice diluted with an equal part of water, being careful not to get the mixture on metal parts. Then wipe the ivory with a damp cloth and buff. Let a professional jeweler scrape and repolish badly stained and yellowed ivory.