The deposition of iron on copper plates by electrolysis. In
electrotyping a thin deposit of iron is thus given the relief plates
before printing from them. The deposit is very hard and exceedingly
thin, so that it does not interfere with the perfection of the
impression in the printing process. As the iron becomes worn it can be
dissolved off with hydrochloric acid, which does not dissolve the
copper, and a new deposit can be given it. Thus the plate may last for
an indefinite number of impressions.

The iron bath may be prepared by immersing in a solution of ammonium
chloride, two plates of iron, connected as anode and kathode in a
circuit. One plate dissolves while hydrogen is given off from the other.
The solution thus produced is used for a bath.

The hardness of the deposit, which is really pure iron, gives the name
of “steeling.”

Synonym–Acierage.