3624. To Repair the Silvering of Looking-Glasses

3624.      To Repair the Silvering of Looking-Glasses. The repairing of the silvering on the backs of looking-glasses has hitherto been considered a very difficult operation. A new and very simple method, however, has been described before the Polytechnic Society of Leipsic. It is as follows : Clean the bare portion of the glass by rubbing it gently with fine cotton, taking care to remove any trace of dust and grease. If this cleaning be not done very carefully, defects will appear around the place repaired. "With the point of your knife cut upon the back of another looking-glass around a portion of the silvering of the required form, but a little larger. Upon it place a small drop of mercury ; a drop the size of a pin's head will be sufficient for a surface equal to the size of the nail. The mercury spreads immediately, penetrates the amalgam to where it was cut off with the knife, and the required piece may now be lifted and removed to the place to be repaired. This is the most difficult part of the operation. Then press lightly the renewed portion with cotton; it hardens almost immediately, and the glass presents the same appearance as a new one.

3625. To Repair a Damaged Mirror

3625.    To Repair a Damaged Mirror. Pour upon a sheet of tin foil about 3 drachms of quicksilver to the square foot of foil. Rub smartly with a piece of buckskin until the foil becomes brilliant. Lay the glass upon a flat table, face downwards; place the foil upon the damaged portion of the glass; lay a sheet of paper over the foil, and place upon it a block of wood or a piece of marble with a perfectly flat surface; put upon it sufficient weight to press it down tight; let it remain in this position a few hours. The foil will adhere to the glass.

3626. Process for Silvering Animal, Vegetable, or Mineral Substances

3626.    Process for Silvering Animal, Vegetable, or Mineral Substances. This process is founded upon the electro-chemical action exercised by certain liquors in which the objects to be silvered are plunged. The method of preparing these liquors is as follows:

Liquor No. 1.- Take 2 parts by weight of caustic lime, 5 of sugar of milk or grape sugar, 2 of gallic acid, and make of them a mixture in 650 parts of distilled water; filter, protect from the air as much as possible, and put in a closely stoppered bottle until the moment of using.

Liquor No. 2.- Dissolve 20 parts nitrate of silver in 20 parts solution of ammonia, and add to this solution 650 parts distilled water. When it is intended to operate, the two preceding liquors are mixed in equal quantities, and, after having been well agitated, filtered. As the solution of ammonia of commerce has not always the same degree of concentration, it would be better, perhaps, to dissolve the nitrate of silver destined for the liquor No. 2, first in distilled water, then mix the solution with liquor No. 1, and then add ammonia in quantity only just sufficient to entirely clear the mixture. The deposition of silver can be accelerated by the employment of heat; in this case, the temperature depends upon the nature of the objects to be submitted to the operation. The method of employing the above liquors in silvering the surfaces of different materials is given in the following six receipts: