Steel Facing.
The life of a photogravure plate without steel facing does not last much beyond 75 impressions, so that if an edition is needed, send the plate to any good printer who will have it steel-faced for you; their charges are very moderate, about 50 cents for a 4 × 6 plate. The steel-facing is accomplished by first making the plate chemically clean, as before preparation for graining, only be very thorough in using an old tooth-brush to get out the dirt and in addition use chloroform before using potash. Then solder a copper wire on to the back. The negative wire is attached to the copper plate. To the positive pole of the quart Smee battery is fastened a bright steel plate same size of copper, in a gallon jar. The plates are hung from glass rods ½ inch apart, a sufficient quantity of the following solution to be poured into the jar:
(Denison's.)
| Warm water | 20 ounces |
| Ammonium chloride | 3 ounces |
| Sulphate of iron and ammonia | 4 ounces |
Filter, and let stand for 24 hours. Five (5) minutes will cover the plate with a thin film of steel.