Antiques, their restoration and preservation / by A. Lucas.

  • Alfred Lucas
Date:
[1932]
Catalogue details

Licence: In copyright

Credit: Antiques, their restoration and preservation / by A. Lucas. Source: Wellcome Collection.

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    dark stains (which are generally due to copper oxide formed from copper present in the gold) these can be removed by the action of strong nitric acid, applied either by immersing the object momentarily in the acid or by smearing the acid on by means of a glass rod or a piece of wood. After the acid treatment, the object should be well washed in water, then in dilute ammonia solution and again in water. Sometimes on ancient gold there are incrusta¬ tions of calcium carbonate or calcium sulphate. No attempt should be made to scrape these oh, as this would scratch and disfigure the gold, but any such deposits may readily be removed by soaking the object in a dilute solution of hydrochloric acid (10 parts of strong acid to 90 parts of water), which is without action on gold. The acid treat¬ ment must be followed by thorough washing in water, then in dilute ammonia and again in water. A number of objects in the Cairo Museum, which were thought to be of solid gold, were much dis¬ figured by an incrustation, that had a metallic appearance, but which on chemical analysis was found to consist of silver chloride in the form of “ horn ” silver. It was further found that these objects were not of solid gold, but were of silver coated with thin sheet gold, and, in one instance, having silver inlay. The silver had become partly
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