Wednesday, August 13, 2008

An Easy Method Of Silvering Mirrors.

         Morison silvering is an operation which is avoided by most photographers as a process in which the successes are few and for the favored. After several failures with the tartaric acid sugar reducing agent for silvering glass, the present writer cast about him for some simpler and more rough and ready method of preparing a reflector for his camera. It has long beam known that it is possible to produce silver minors by the use of formalin as a reducer. The method, however, has not come into practical use because the deposit of silver is usually so granular that it will rob of the glass upon the least touch. The following formula provides a means of silvering glass and ether substances with ease and rapidity, and the process is a fascinating one to watch.

Stock Silver.

Silver nitrate………………………45grs. 3gms
Distilled water…………………….10ozs. 300c.c.s

Stock Formalin.

Formalin (40 p.c. Formaldehyde)....1oz. 45gms.
Distilled water…………………….10ozs. 450c.c.s.
Methyl Violet dye…………………10grs. 1gm.
Thaw solutions improve on keeping.

         The following quantities are sufficient for 20 square inches of glass allowing for waste silver being deposited on the dish and elsewhere.
         Take 3 ozs. (90c.c.s.) of the stock silver solution and add 10 per cent, ammonia solution drop by drop (a fountain pen tiller is heady for this), shaking the mixture after each addition. The mixture first becomes turbid, and then gradually clears. When dear, atop adding ammonia. A slight excess of ammonia is not detrimental. In another receptacle poor out 3 drachmas (11 c.c.s.) of the stock formalin solution.

The Silvering Process.

         Take the piece of glass it is intended to silver, and clean it well with whiting and water, or by any other method that may in favored, and rinse it under the tap, swabbing the surfaces with cotton wool. Now rub the wet face of the glass with another piece of cotton wool which has been soaked in the following priming solution:

Tin Protochloride (Stannous Chloride) 26 grs. 1gm.
Water ………………………………….10 ozs. 200 c.c.s.

         Ordinary tap water will do. This solution should be thrown away when done with.
Rinse the glass under the tap and wipe it with a piece of cotton woo) which has been dipped in distilled water.
         Place the glees face up in a developing dish which has previously been cleaned with nitric acid and rinsed with distilled water. The next operation is to add the formalin to the ammoniosilver mixture, and immediately pour into the dish, and to rock the dish well.
         The silver begins to deposit at once on the primed surface, the solution becoming darker after a short time, and then slowly clearing. After from one to two minutes the solution reaches its maximum clearness, the by-products of the reaction forming into little grannies. At this point ran tsp water into the dish and lift the mirror out and rinse it, finally swabbing with a soft piece of wet cotton wool.
         Allow the mirror to drain for a minute or two, and remove any drops of water from the surface by lightly touching them with a piece of blotting paper. After half an hour or so the mirror should be quite dry and ready for burnishing.

Finishing the Mirror.

         When dry, the mirror should have a brilliant surface, with a slight yellowish tarnish, which must be removed by polishing if the front of the mirror is to be used as a reflector.
         For polishing and burnishing the surface, take a piece of a couple of inches square, or, failing this, a piece of really soft cotton rag, and tie it round^ a plug of cotton wool, to as to form a medium soft pad. Keep this in an old plate-box with some rouge. The rouge may be bought at a chemist's, or in some households purloined from the feminine dressing-table. Jeweler’s rouge is sometimes too coarse. The wash-leather pad should be lightly charged with the rouge.
         Warm the mirror and the pad slightly so as to be sure that no moisture is present, and then lightly rub the surface with rapid small circular motion. The mirror will take a brilliant polish and is then ready for use.

General Consideration.

         Practically speaking, the hotter the glass 'before applying the silvering solution, the whiter and more granular the resulting mirror will be. Cold solutions produce quite a good deposit, which is dark in colour on the surface, but which takes a brilliant white polish. The best temperature is about 70 to 80 F. It is a good plan to have the glass a few degrees warmer than the solutions. This can be accomplished by immersing the glass in tepid distilled water for a few moments before silvering.
         Celluloid may be easily silvered by exactly following the procedure as for glass.
Mirrors may 'be silvered face down if desired. It is a question more of convenience than actual merit.
         Silver may be prevented from depositing on unwanted parts by painting those portions with Vaseline or celluloid varnish previous to priming with the tin solution.
         Spent solutions are hardly worth saving, even when there is a quantity. Most of the silver in the solution comes down as actual mirror surface.
Methyl violet dye has the property of keeping the surface of the mirror brilliant and unclouded. Its action is analogous to that of bromide in a developer. It may be omitted if not available.
         The priming bath gives a much more adherent coating. It also has the property of attracting most of the silver to the working surface, instead of too generously distributing it on the sides, and bottom of the dish. It is supposed that a silicate of tin is formed on the surface of the glass. This, however, cannot 'be the case with celluloid or other non-glass surfaces.
         The cost of silvering 20 square inches of glass, reckoning silver nitrate at 4s. per oz., is about 2d. As failures cost as much as successes, it is a good plan to practice on small pieces of glass before attempting a larger surface. One has, for example, to learn how to clean glass properly.
         Well boiled-water can in most districts be used instead of distilled water.
         As a protection against oxidation, the mirror may be varnished with celluloid varnish. The coating of varnish should not be too thin or it will dry with a smoky surface. No other varnish is suitable for the purpose, because silver reacts with most gums, etc. It is, however, easy to resilver a mirror when the surface is worn away by repeated republishing that in most oases it is hardly worth while to decrease the efficiency of the reflecting surface by varnishing it.
         Measures, beakers, and dishes should be cleaned after us& with strong nitric acid, or the remnants of silver will give trouble when the vessels are used for other purposes.


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