One-Way Window Glass
Caution: Chemicals and ready-to-use solutions will cause stubborn stains on hands and clothing.
Clean glass with soap and water, then rinse thoroughly, handling the glass on the edges, only. Let glass dry.
Use a small mop, or make one with cotton on a stick. Pour a little NITRIC ACID on the surface of the glass and spread it around with the mop. Flush the surface with water, then place the glass face down in a basin of clean water, to keep it clean until you are ready to treat it.
Get five (5) clean glasses. In one make Solution A, by dissolving one ounce of SILVER NITRATE in ten ounces of DISTILLED WATER. Set aside one ounce of this solution to use later. Then, with a medicine dropper and constant stirring with a glass rod, "ammoniate" your Solution A, by adding, drop by drop, some strong 10% to 26% AQUA AMMONIA. At first a thick, brownish mass will appear, but as more ammonia is added this will begin to thin out. Stop adding ammonia when the solution has become just barely cloudy, not entirely clear.
Next, in a separate container, mix one ounce of caustic potash, known as POTASSIUM HYDROXIDE, with 10 1/2 ounces of water. Note: slowly add the caustic to the water. NEVER add water to the caustic. Pour this solution into the ammoniated silver nitrate solution and stir very thoroughly.
Then again, add strong ammonia water, drop by drop, until the solution, just clears. Now, pour the remainder of the Non-Ammoniated Silver Nitrate solution, this is the portion originally set aside. The main solution would once again become slightly cloudy. Make a solution of 1/2 ounce of GLUCOSE in ten ounces of Distilled Water and stir it into the main solution, which is now ready to use. This glucose is also know as dextrose, or just plain corn sugar.
The "slivering" should be done on a level table. Remove the glass from the basin and set it on edge to dry, then support it, sterile face up, on the corners of four upturned identical highball glasses, or the like. Place a small mirror, under the glass, at an angle (this will enable you to see the reflection of the silvering process so that you can stop at the right time).
Pour enough solution on the glass to cover it, leave it undisturbed until the desired film of silver has been deposited. By looking at the mirror which you have placed on the table, at a slight angle, facing upwards, you are able to see the reflection of the silvering process and stop at the moment when the right degree of reflection and transparency has been achieved. This will usually be about 20 minutes.
Then tip off the solution at one corner and thoroughly flush with running water. Set the glass on edge and let drain dry. WITHOUT touching the delicate film. When thoroughly dry, put on a coat of clear VARNISH with a soft CAMEL-HAIR BRUSH, or better, with a spray gun. When this dries, you may choose to further protect the silvering by taping to the transparent mirror another sheet of plain, clean glass of the same size.
In use, the light on the mirror side should be stronger than on the back, and you should be able to see everything clearly through the mirror from the back; while anyone on the other side sees nothing but an ordinary mirror. Should you not be able to see clearly through the mirror, you have allowed the silvering process to continue too long. In order to achieve perfection, practice with small mirrors, until you have the timing just right. Such mirrors, as small as 8"x12" have sold for as much as $12, which is of course far more than your cost to make. Good Luck!
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