Oxidizing Silver
American Watchmaker and Jeweler (1892)
Important: Safety Warning
This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
1. Place the silver or plated articles in a solution of liver of sulphur diluted with spirit of sal-ammoniac. They are then taken out, washed, dried and polished. This produces a blue-black tint, while a solution of equal quantities of sal-ammoniac and blue vitrol in vinegar gives a brown shade. 2. Sal-ammoniac, 2 parts; sulphate of copper, 2 parts; saltpeter, 1 part. Reduce these ingredients to a fine powder, and dissolve in a little acetic acid. If the article is to be entirely oxidized, it may be dipped for a short time in the boiling mixture; if only in parts, it may be applied with a camel-hair pencil, the article and the mixture both being warmed before using. 3. There are two distinct shades in use, one produced by chloride, which has a brownish tint, and the other by sulphur, which has a bluish-black tint. To produce the former it is only necessary to work the article with a solution of sal-ammoniac; a much more beautiful tint, however, may be obtained by employing a solution composed of equal parts of sulphate of copper and sal-ammoniac in vinegar. The fine black tint may be produced by a slightly warm solution of sulphate of potassium or sodium. Silvering for Copper or Brass. Mix I part of chloride of silver with 3 parts of pearl ash, 1 1/2 parts common salt, and one part whiting; and well rub the mixture on the surface of brass or copper (previously well cleaned), by means of a piece of soft leather, or a cork moistened with water and dipped in the powder. When properly silvered, the metal should be well washed in hot water, slightly alkalized, then wiped dry. 2. Mix three parts of chloride of silver with 20 parts finely pulverized cream tartar, and 15 parts culinary salt. Add water in sufficient quantity, and stir until the mixture forms a paste, with which cover the surface to be silvered by means of blotting paper. The surface is then rubbed with a rag and powdered lime, washed, and rubbed with a piece of soft cloth. The deposited film is extremely thin.
What Has Changed in the Last Century
The core trick described by the American Watchmaker and Jeweler in 1892 is still the standard one: dip or paint silver with liver of sulphur (potassium sulphide) and you get the blue-black finish, sold today as "liver of sulfur" in lump or gel form and used by jewellers exactly as described, though modern shops work with gloves and ventilation and buy ready-mixed proprietary patinas rather than compounding sal-ammoniac and blue vitriol in vinegar. The name has quietly been corrected: the dark film is silver sulphide, not an oxide, so "oxidized silver" survives only as a trade term for what chemists call a sulphide patina. The second half of the entry has genuinely gone obsolete — rubbing a paste of silver chloride, salt and cream of tartar onto brass with a cork gave the "extremely thin" film the writer admits to, and such work is now done by electroplating or commercial immersion baths that deposit a measured thickness. The safety note above is the real gap in a century: these recipes were printed for tradesmen with no warnings at all.
Written for this edition, 2026.