Caring for Your Gold & Ormolu
Pure gold will not corrode under normal conditions. However, it is very soft, so most 'gold' objects contain other metals such as copper and silver. These can corrode and discolour the surface of the gold. Any chemical treatment should be left to a specialist.
Cleaning gold & ormolu
Please read the Basic Guidelines page before attempting to clean your object.
Cleaning gold and ormolu (see below) should be limited to gently dusting with a soft brush. If the surface is discoloured, use a swab moistened with methylated spirit and rub gently. If this doesn't work, try a swab moistened with spit, followed by a swab moistened with distilled water.
Warning: some gold objects, especially from the Indian subcontinent, and parts of Asia, have intentional deposits of reddish material in low areas, used to enrich the appearance of the metal. Natural substances such as tamarind seed were used and can be mistaken for residues of polishing compounds. If in doubt, consult a specialist before cleaning.
Ormolu is the term used to describe gilt brass on decorative art objects from the 18th and 19th centuries, for example gilded mounts on furniture. The gilding was applied using the mercury amalgam process, sometimes also called fire gilding. Copper corrosion products can form on the gold surface through minute gaps in the gilding.
The traditional method for 'cleaning' ormolu was to brush or dip the ormolu in an ammonia solution. This was very effective for removing copper corrosion products but unfortunately ammonia also attacks the metal itself. Ammonia 'cleaning' often left the surface slightly matte, so dipping was followed by polishing to restore a bright shiny gold finish. The first treatment with ammonia often produces rapid and spectacular results. Repeated treatments, however, damage both brass and the gilt layer. Eventually all gilding is destroyed and even the brass becomes etched and dull, leaving a once attractive and valuable piece almost worthless.
Ormolu should be cleaned in the same way as gold. As with silver gilt objects, the gold layer is thin, soft and easily polished away. Small black spots can often be seen on ormolu. These are typically very hard and difficult to remove without damaging the gilding layer. Chemical treatment is needed to remove 'black spot', so consult a conservator.