SILVERING SOLUTION.

To any desired quantity of chloride of silver in water add, little by little, cyanide of potassium, shaking well at each addition, until all the cyanide is dissolved. Continue this operation, and add the cyanide, until all the precipitate is taken up and held in solution.

This solution is now ready for the plate-cup. Enough water may be added to cover any sized plate when held perpendicular in the cup. The strength of the solution may be kept up by occasionally adding the chloride of silver and cyanide of potassium. There should alway be a very little excess of the cyanide.

The plate should be well cleaned and buffed, and the solution well stirred before it is immersed. Care should be observed to keep the solution clean, and allow no particle of dust to come in contact with the surface of the plate. The plate is now to be attached to the pole of the battery.

After remaining a short time, it assumes a blue color; take it out, rinse freely with pure water, then dry with a spirit lamp, and it is ready for buffing. Buff and coat in the usual manner. Some operators are in the practice of immersing the plate in the solution and buffing twice. This additional silvering is no improvement wherever there has been a proper first coating.

Sometimes the operator is troubled with streaks or scum on the plate. This may arise from three causes, all of which experience must teach the experimenter to avoid; first, too great an excess of cyanide in the solution; second, a lack of silver; third, the current too strong. Another annoyance arises from the solution being dirty and the dirt collecting on the surface. When this is the case, the dirt is sure to come in contact with the surface of the plate as it is plunged into the solution, and the result is a scum that it is difficult to dispose of. This can be prevented only by frequent filtering. One thing should always be borne in mind in electrotyping Daguerreotype plates--that in order to secure a perfectly coated surface, the plate should be perfectly cleaned. In this point, many who have tried the electrotype process have failed, attributing their ill success to other than the proper cause.