Philip Quanjer, Else Quanjer
Staining silver black
One of the final steps in finishing your casting or etching of an image in silver (if you are an enamelist you might use niello) may be to turn the depressed areas black. This can be achieved by chemically binding silver to sulphur, using calcium sulphate (liver of sulfur). This is available in the form of granules, but it has a short shelf life when exposed to air and light. It is also available as 'Blitz stain' (Schwarzbeize Rapid, produced by Schering), a watery solution of sodium sulphide and an alkaline selenium compound (the pH is larger than 13!).
- Heat the silver so that it is lukewarm. Apply the stain with a painting brush to the areas that you want to stain black.
- Heat the silver, for example with a match or lighter, but do not make it very hot. Thus one speeds up the chemical binding and obtains a more saturated black.
- Use a solution of 1 part sulphuric acid and 9 parts of water as a fixing bath. Prepare the solution by adding sulphuric acid to water, do not do it the other way around!! Wear rubber gloves while you do this. The acid makes the silver quite bright again.
- Carefully remove all chemicals while holding the object under lukewarm, running water.
- Remove any unwanted stains by sanding and polishing the surface.
