A technical dictionary of printmaking, André Béguin.

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Steelfacing
A plating process in which a copper plate is covered by a thin coat of iron by means of an electroplating procedure. The iron layer is deposited in order to reinforce and protect an engraved plate since copper is quite fragile.
In fact, the rollers of a printing press soon crush and stop up the lines of a copper plate, especially if the plate is cut and the burr* has been left (the burr gives a particularly velvety finish to a line [ * drypoint ]). The wiping of intaglio plates before printing and even the inking procedures contribute to wearing the plate down. Furthermore, all copper plates are exposed to the dangers of scratching.
A plate that has undergone a proper steelfacing can be used to print a large number of impressions depending on the way the inking is done, how the plate is wiped, and what engraving technique was used in making the plate. In any case, such a plate can print anywhere from several hundred to several thousand impressions. The most fragile are, of course, dry point plates which, despite a good steelfacing, will sometimes not print more than 300 to 500 impressions without being worn down. Nevertheless, this is far more than the 20 or 30 impressions that can be made with an unprotected dry point plate. On the other hand, line engravings with deep and precise lines can be used for pulling as many as 10,000 impressions. It may therefore be said that steelfacing will always guarantee at least an artist's edition since these editions are usually limited to a maximum of 300 copies. The steelfacing of a plate will ensure that an entire edition maintains a constant image quality. If the plate does not hold out it can always be steelfaced again when the copper begins to show through. Removing the steelfacing is quite easily done.
Steelfacing is usually done by specialists. It requires a welding job done on the back of the plate so that it can be suspended in the electroplating vat. Only the welded area will remain clean whereas the rest of the plate will be covered by a layer of steel. Before putting it into the vat, the plate must be cleaned with a potassium solution or with hot soda so as to clean out the intaglio lines and remove any traces of grease. The scouring procedures should be completed by a final cleaning with a lightly diluted nitric acid solution. At this point the plate can be put into a solution composed of water (1 liter), ammonia chloride (100g) and ferrous sulphide (50g) for about 15 minutes. The vat used for this purpose should be made of slate, stoneware or wood covered in lead (or plastic). The plate to be steelfaced should be suspended so as to face another plate made of steel. The latter must be connected to a positive pole of a low tension, continous current supply. The distance between the two plates should be set at a few centimeters and the strength of the electrical supply should be about 4 volts. Once the electroplating is done the steelfaced plate must be rinsed, dried, and the welding removed. At this point it (the plate) should be covered with a protective varnish since the plate will now oxydize as quickly as any steel plate. If one does not wish to use a varnish one can use some vaseline or gun grease and cover the plate with a sheet of tissue paper. A good steelfacing job can be judged by the fact that the deposited steel is rather shiny. A mat finish on a steelfaced plate indicates that too high a voltage was used for electroplating.
Very slight steelfacings are also done but are only used for trial printings. These plates are then stripped so that the necessary corrections can be carried out.
The removal of a steelfacing is done by putting the plate in a bath made up of 10% sulphuric acid. The bath must be followed up by rinsing and cleaning with a 2% solution of sodium cyanate. A final rinsing and drying must then be carried out.
Steelfacing was invented by Salmon and Garner who took out a patent for it in 1857. The process was slightly improved upon shortly thereafter by Jacquin. The Cioconda of Calamata was the first steelfaced copper plate to be printed.
Zinc plates cannot be steelfaced directly as they must first be copper plated. Iron can be steelfaced superficially with potassium ferrocyanate.
Although steelfacing is the most frequently used protective technique in print making it is not the only one. Chrome plating is also practiced since it makes the plate even more resistant. Chrome is used for photogravure plates but it can also be used to protect engraved plates. It is, however, a more complicated process which requires rather complex equipment in order to ensure that the plating is both thin and regular. The chrome plating of intaglio plates presents the advantage of being easy to wipe after inking.
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