Provision must be made for supporting the glass in a perfectly horizontal position at the surface of the liquid. This is best done by cementing to the face of the mirror three nice hooks by which it may be hung from a temporary framework - easily made out of a few sticks.
The glass to be silvered must be cleansed by immersing it in strong nitric acid, washing in liquor potassee, and thoroughly rinsing with distilled water. If the glass has had mercurial amalgam on it, it will probably be necessary to clean the back with rouge. On having this surface perfectly, chemically clean, depends in a great measure the success of the operation.
Having arranged the contrivance for suspending the glass so that it may be at exactly the right height in the vessel that is to receive the solution, remove this vessel and pour into it enough of equal quantities of the two solutions to fill it exactly to the previously ascertained level. Stir the solutions so that they will become thoroughly mixed, and replace the glass to be silvered, taking great care that the surface to be silvered shall come in contact with the silvering fluid exactly at all points. The glass plate should be rinsed carefully before replacing, and should be put in while wet. Great care should be taken that no air bubbles remain on the surface of the solution, or between it and the surface to be silvered.
Now set the vessel in the sun for a few minutes, if the weather be warm, or by the fire, if it be cold, as a temperature of 45° to 50° C. (113° to 122° Fah.) is most conducive to the rapid deposition of a brilliant, firm and even film of silver. The fluid in the sunlight soon becomes inky black, gradually clearing as the silver is reduced, until when exhausted it is perfectly clear. The mirror should be removed before this point is reached, as a process of bleaching sets up if left after the fluid is exhausted. From 20 to 80 minutes, according to the weather, purity of chemicals, etc., is required for the entire process.
When the mirror is removed from the bath, it should be carefully rinsed with distilled water from the wash bottle, and laid on its edge on blotting paper to dry. When perfectly dry, the back should be varnished with some elastic varnish and allowed to dry. The wires and cement can now be removed from the face, and the glass cleaned with a little fledget of cotton and a minute drop of nitric acid, taking great care that the acid does not get to the edges or under the varnish. Rinse, dry and the mirror is finished.