Bronze Liquid
American Watchmaker and Jeweler (1892)
Important: Safety Warning
This page contains a formula or preparation using substances now known to be dangerously toxic, such as arsenic, mercury, lead, or cyanide compounds. Exposure to these substances can cause severe poisoning, permanent injury, or death.
In addition, 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.
Dissolve sal-ammoniac 1 oz.; alum, 1/2 oz.; arsenic, 1/4 oz.; in strong vinegar, 1 pt. The compound is immediately fit for use, and, where the metal is good, is seldom found to fail. Bronze for Medals. The following process of bronzing is carried on in the Paris mint. Powder and mix 1 pound each of verdigris and sal-ammoniac. Take a quantity of this mixture, as large as a hen's egg, and mix into a dough with vinegar. Place this in a copper pan (not tinned), boil in about 5 pints of water for 20 minutes, and then pour off the water. For bronzing, pour part of this fluid into a copper pan; place the medals separately in it upon pieces of wood or glass, so that they do not touch each other, or come in contact with the copper pan, and then boil them in the liquid for a quarter of an hour. Bronze for Steel. Methylated spirit, 1 pint; gum shellac, 4 ounces; gum benzoin, 1/2 ounce. Set the bottle in a warm place, with occasional agitation. When dissolved, decant the clear part for fine work, and strain the dregs through muslin. Now take 4 ounces powdered bronze green, varying the color with yellow ochre, red ochre and lamp black, as may be desired. Mix the bronze powder with the above varnish in quantities to suit, and apply to the work, after previously cleansing and warming the articles, giving them a second coat, and touching off with gold powder, if required, previous to varnishing.
What Has Changed in the Last Century
The 1892 American Watchmaker and Jeweler hands the reader an arsenic-and-vinegar dip as casually as a recipe for salad dressing, and even the milder Paris Mint method relied on verdigris, a copper acetate now handled as a poison. Arsenic and its compounds are today classed as proven human carcinogens and their use in workshops is tightly restricted, so no jeweller mixes such a bronzing liquid over an open pan. The chemistry of colouring metal, however, has not been abandoned: modern patination still works by controlled corrosion, using ferric nitrate, cupric nitrate, liver of sulphur and ammonium chloride — the same sal-ammoniac the old text names — applied under extraction and with gloves. Electroplating and lacquered pigment coatings, the direct descendants of the shellac-and-bronze-powder "bronze for steel" recipe, now do most of the commercial work.
Written for this edition, 2026.