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Silvering Mirrors

By D. McClanahan

The art of silvering mirrors has been held as a valuable trade secret for many years, but the formulas and instructions here given makes it possible for any one with ordinary care and a little patience to do the work successfully. I have endeavored to write these instructions in order that you may not become confused.

First you must have a clean room free from dust, in which place a steam table made as per instructions, tho this is not absolutely necessary, as you can warm the glass up to 80° to 100° F. by pouring warm distilled water on the same. But for those who anticipate silvering mirrors to any extent a steam table will be found necessary. The size of the table I will leave to you, tho would suggest to make the table small, say three by six feet, until you become more proficient in the art.

Make a box three by six feet, open at the top; for legs use two by four timber. Bolt the legs to the box frame at A, Fig. 1. Next take a piece of iron three feet long, two inches wide and one-quarter inch thick, placing it across each end so the steam pipes may rest upon it, B, Figs. 1, 2, 3. This is to prevent the boards on the bottom of the table from burning. Place one-inch pipes in the table as in illustration, Fig. 3-C ; on top of the pipes is placed an iron top, three by six feet and one-quarter inch thick.

(Note.—It is best to go to a foundry and secure your iron plate first and build your frame work to fit the plate, for sometimes it is hard to get iron plate the exact size you want it.)

This iron top must rest flush with the side boards D, Fig. 1. This is done by making a quarter-inch groove on all four sides of the table. Now cover the iron top with unbleached muslin, stretch and tack to the side boards.

Make a wooden gutter all around the table, E, Figs. 1 and 3, about three inches wide, and at F, Figs. 1 and 3, make a hole and place a spout in it. The table is connected to a steam boiler or hot water heater, using suitable valves V, V, as shown, to control the steam inlet and outlet pipes.

Do not attempt to handle a very large glass at first. One a foot square will be large enough to start with. Obtain a good grade of plate glass free from scratches.

Next get some polishing rouge, which comes in powdered form. Place in a bag made of two or three thicknesses of cotton flannel, sew bag up, place in water to soak, then take the rouge bag and rub over the glass while the rouge is still wet ; then rub well with your polisher, Fig. 4. This is a block of wood measuring six by three inches, having two handles for holders, B, Fig. 4, with a thick felt rubber attached at the bottom, C, Fig. 4. Keep the felt wet and proceed to polish the glass all over the surface that is to be silvered, being careful to. polish right to the edges. When the rouge has dried, wipe it off. When thru polishing avoid touching the polished side with your fingers, as this would leave a grease spot and the silver would not adhere to the glass where you touched it. Put your hands under the glass and place it on your washing table and clean as follows:

Washing Solution

Take one- fourth ounce of muriate of tin crystals to ten ounces of water, and from this solution take one ounce and add it to one pint of water. This one pint of water should look a very light blue in color. Now pour on the glass and rub off with a felt block like Fig. 4, but minus the handles.

Be sure to rub only one way, then pour on a lot of hydrant water, rubbing it off with another felt block. Place your hands under the glass and put it on the steam table, which has been previously warmed up to 90° to 100° F. Keep the side to be silvered up. Now level the glass by placing wooden wedges, see Fig. 5, under the edges. Pour warm distilled water on the glass in the same manner as the silver solution will later be poured on.

By pouring distilled water on glass and placing wedges as may be needed you can level the glass until you have an even layer of water standing all over it. Should the distilled water be slow in covering the edges, take your glass rod and draw the water by scraping along the edges. When you get the glass level, raise one side slightly and let all the distilled water run off, laying the glass back in place gently, being very careful not to displace the wedges, thereby making the glass unlevel.

How to Silver

Pour your silver solutions No. 1 and No. 2 into a glass or stone pitcher, using the exact proportions as given in the formula below, stirring the solutions with a glass rod or by pouring from one pitcher to another. Now pour into the center of the glass without stopping as the precipitation commence-- at once, or as soon as the solutions are mixed.

Let the solution flow out until the entire surface is covered, allowing it to stand thirty or forty minutes to precipitate, then tip the glass on one corner, allowing all the solution that will to run off.

Next clean by pouring on the hike-warm distilled water, place the glass back on the wooden wedges for a few minutes to dry. When dry coat the side that is silvered with a mixture of orange shellac— two ounces; wood alcohol, one pint; turpentine six ounces. Use a camel's hair brush to smooth it out—after this is dry, paint over with a camel's hair brush and some asphaltmn varnish.

The Boiled or Cold Process

Solution No. 1—Take 150 grains of nitrate of silver. AgNO3, crystallized salt C. P., dissolve in 1 pint of distilled water and to this add with a glass eye-dropper concentrated or 26% ammonia, one drop at a time, until it turns dark keep on dropping the ammonia until it turns light again—then put in 130 grains more of silver, AgNO3 and let it dissolve-now pour this into 3 pints of distilled water first measured out. Have a ribbed funnel and in the neck of same press a little absorbent cotton before you put in the filtering paper—now put in the ribbed funnel two sheets of filtering paper and filter the solution— it is then ready for use.

Solution No. 2—Take 96 grains of crystallized Rochelle salts, place in one-half gallon of warm distilled water, using a porcelain lined vessel. Let this come to a strong boil for about two minutes, then add 96 grains more of AgNO3 and let for six minutes longer. As soon solution is cool, it is best to pour it from the porcelain vessel in which it was boiled into some glass vessel, as the vessel that you boiled this solution in will be quite dirty. Filter this solution the same as you did solution No. 1—into a separate pitcher—when ready to silver mix the two and flow on the glass. Let stand for 15 or 20 minutes.

The Caustic Potash Process

Solution No. 1—Take 3 pints of distilled water—measure from this amount 4 ounces and add to the four ounces of distilled water 240 grains of AgNO3-let dissolve - then take concentrated or 26% ammonia, 3 1/2 drachms and add it drop by drop until the sediment is nearly redissolved then add the balance of the water—let this stand 12 hours and filter.

Solution No. 2—Take 48 ounces of distilled water and divide into 3 parts and add to the first part 180 grains of AgNO3. add to the second part 20 grains of caustic potash—add to the third part 1 3/4 ounces of crystal Rochelle salt C. P. Mix all three—shake well and let stand for 12 hours and filter. To use, mix 4 parts of Solution No. 1 and 1 part of Solution No. 2-stir with a glass rod and pour on glass at once—allowing 35 to 40 minutes to precipitate.

The French or Tartaric Acid Process

Solution No. 1—Take 8 ounces of AgNO3, dissolve in 8 ounces of concentrated or 26% ammonia—when the silver has dissolved add 1/2 pint of distilled water and let it stand 24 hours—filter and it is then ready for use.

Solution No. 2—Dissolve 8 ounces of tartaric acid in one quart of distilled water, let it stand for 24 hours—the older this solution gets the better. Reduce this to 10% by using an acid hydrometer—if it should be stronger than 10% add distilled water until it becomes so. Filter before using.

To silver, take 4 ounces of Solution No. 1, put it into 1 quart of distilled water. Take 4 ounces of Solution No. 2, put it into 1 quart of distilled water—next mix Solutions No. 1 and No. 2 by pouring from one pitcher to another—then flow the solution on the glass, allowing it to remain for one hour.

Metallic Mirror Process

Make a liquid preparation by melting into a porcelain vessel 1 dram of lead, 1 dram of tin, 1 dram of C. P. Bismuth. When these are melted together add 10 drams of mercury before the mass has cooled. The mercury will cool it sufficiently for use. Lay the glass flat with the clean side up and pour the metallic liquid over it, completely covering. Raise the glass almost perpendicular, letting the amalgam drain off. When the coating has become hard and dry, coat with drop black ground in Japan, and then thin with turpentine.

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