Zinc-plating
The Encyclopedia of Founding (1892)
Important: Safety Warning
This page contains instructions involving gunpowder or other explosive or pyrotechnic compositions. Preparing explosives as described has caused severe injuries and deaths, and is illegal in most places.
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.
See GALVANIZED IRON. Zinc, Reducing the Oxide of.--Have a large pot that will hold about five hundred pounds of the oxide; place it over the fire and fill it with the dross, etc., then pour sufficient muriatic acid over the top to act as a flux. The action of the fire will melt the dross, and the pure metal will fall to the bottom. Zinc, To Purify.--Granulate zinc by melting, and while very hot, pouring it into a deep vessel filled with water. Put the granulated zinc in alternate layers with one fourth its weight of nitre in a Hessian crucible, and with an excess of nitre on the top. The crucible must be covered and the lid secured; then apply the heat. When deflagration takes place the crucible can be taken out, the metal freed from slag, and poured. Zinc treated thus is freed from arsenic and other impurities. Zinc-white, or zincic oxide, is a strong base, forming salts isomorphous with the magnesian salts. It is prepared either by burning zinc in atmospheric air or by heating the carbonate to redness. Under the name of zinc-white it is frequently substituted for white lead as a pigment for paints. It is prepared on a large scale by volatilizing metallic zinc in earthen muffles, the vapor from thence passing into a receiver, where, coming in contact with a current of air, it is oxidized. The oxide, being a light woolly substance, is carried along tubes to the condensing-chamber, where it falls as a fine powder, or zinc-white.
What Has Changed in the Last Century
The 1892 Encyclopedia of Founding sent readers to "GALVANIZED IRON" and described zinc work as a hand craft of pots, muriatic acid and crucibles of nitre; coating steel with zinc is now a continuous industrial process, transformed by the Sendzimir continuous hot-dip line of the 1930s, which feeds steel strip through molten zinc at mill speed for car bodies, roofing and fencing. Electroplated zinc, once done in highly poisonous cyanide baths of the kind the page's safety warning flags, is now mostly laid down in alkaline non-cyanide or acid chloride solutions. The zinc-white the entry praises as a substitute for white lead has itself largely been displaced as a paint pigment by titanium dioxide since the 1920s, though zinc oxide remains a heavy-tonnage additive in rubber tyre compounding and a standard sunscreen ingredient. What has not changed is the underlying chemistry: zinc still protects iron sacrificially, corroding in its place.
Written for this edition, 2026.