Articles by Rick Glawson
Glue Chip - Standard Method / Glue Chip - Rawson Evans Method / Glass Silvering / Angel Gilding Process / Lead Nitrate Deposition / Hydroflouric Acid/Mica Glass Embossing Process / Guide to Laying Abalone / Material Safety Data Sheet for Hydroflouric Acid
The silvering solutions consist of three parts and are coded by color. GREEN- silver, BLUE- activator, RED- reducer, also referred to as the depositing agent. All three solutions are in concentrated form and must be diluted with distilled water.
You should acquire three quart sized containers of either glass or plastic with screw or snap caps and a couple of pint (16oz.) spray bottles.
Mark one of the empty quarts "GREEN" or "A", the second one "BLUE" or "B", and the third one "RED" or "C".
Using the small provided measuring cup, pour one ounce (30ml) of the green concentrate into the quart marked "GREEN" and fill with distilled or de-ionized water, cap, SHAKE WELL and thoroughly wash out the measuring cup with tap water.
Now follow the same procedure for both the BLUE and RED solutions in their respectively marked bottles. When not in use, keep them capped and in a cool location. Refrigeration is not necessary. These have a long shelf life.
For the "TINNING" solution, mix into one of your spray bottles, one scoop (approx. ½" of the front end of an ice cream stick) from the container marked "STANNOUS CHLORIDE" with eight ounces of distilled water. This dilute solution MUST be made up fresh each day.
The orange/black granules marked "SILVER STRIP" are mixed into regular tap water in a proportion of approx. one volume ounce of granules to one pint of water. Mix these up in you other spray bottle. The shelf life is indefinite. The active ingredient is Chromic Acid (an oxidizer), and is used to remove unwanted silver deposits. The proportion suggested is fairly strong and can be diluted further to as much as four ounces per gallon of water. In either case, it will not burn your hands or damage areas of protected silver. As with any chemicals, the use of disposable gloves and common sense prevails. Any dark brown stains you may acquire on you skin can be removed by applying a little of the solution on the stained areas, rubbing a bit, and washing it with soap and water.
PREPARING THE GLASS FOR SILVERING
You first want to remove any and all grease, dirt, and cutting oil from the surface. Common dish soap and water, ammonia or Bon Ami cleaning cake in conjunction with a sponge or felt blackboard eraser dissolves and removes any contamination without adding any of it's own. Without allowing it to dry, thoroughly rinse off all cleaners with tap water and a separate pad. When cleaning, be sure to include the outer edges to eliminate any oil. Remember that the silvering chemicals are water borne and that water and oil don't mix. If you notice any of the rinse water repelling from the edges of the glass, repeat the cleaning step. Observation is your best guide.
If portions of the glass have been glue chipped (using aluminum oxide as the blasting medium) or wheel engraved with aluminum oxide wheels, unseen aluminum deposits may be on the surface, which can be removed with a lye solution. Red Devil or equivalent household lye drain cleaner mixed 50/50 with water and swabbed over the surface is a good practice. If aluminum residue is present on the surface, it will turn black when the silvering chemicals are applied. Do this procedure before the first soaping to assure no lye remains on the surface. Also, if your glass has been glue chipped, be sure all bits of remaining glue have been sufficiently soaked with water and scrubbed off before the cleaning process.
As a principle, it is always best to keep the glass wet throughout the entire silvering process. If you wish to only silver a selected area, you can apply a hot glue dam around the desired area. In doing so, make sure the glass is dry and apply a heavy bead of the glue. The yellow colored glue sticks work best and bear in mind that if you should get serious with this style of work, there are highly efficient professional hot glue applicators available. The hobby and hardware guns work well for occasional use but are slow. Do not try to dam an area with caulking, tape, or anything that will dissolve or migrate with water. Now, re-flood with tap water, and we're back to where we left off.
TINNING THE GLASS
Tinning, or priming the glass with Stannous Chloride solution is necessary to create a bond between the silver and the glass and to insure longevity. During the cleaning process, we used only tap water, which is both acceptable and economical for cleaning and pre-rinsing. Because it could contain chemical traces injurious to the silver, we will final rinse with distilled water. swilling off the remaining tap water. Tilt the glass to drain off the excess distilled and spray or pour a heavy layer of tin solution over the surface. With the glass lying horizontal, allow it to remain for half a minute or so, occasionally rocking the panel to insure even coverage. Add additional tin as needed. Now pour off the solution and rinse thoroughly with tap water followed by hot or warm distilled water. The silvering seems to be more uniform if the glass is warmer than the silvering solutions. Preformed in a comfortably warm shop, you shouldn't have to warm the water. Place the panel horizontal on a flat level surface and add a little extra distilled water to prevent drying while you measure up the silver. The use of a bubble or spirit level and some wooden wedges will ensure its flatness.
In setting out your quarts before you, provide a graduated measuring cup in fluid ounces for each of the three flavors. The object being you want to dispense out one fluid ounce of each color for every square foot of surface being silvered, and to keep each dispensed chemical separate from one another until they are combined for use.
As an example, let's say your glass measures 18 x 24 inches, 18 x 24 = 432 square inches, divided by 144 gives you 3 square feet.
Dispense 3 ounces of GREEN solution into its cup, 3 ounces of BLUE into its cup, and the same for the RED. Returning to your glass panel, pour off the water and lifting vertically, shake off the excess. Of course with large panels you can only lift up a side and pour off the runoff. If you have first leveled your panel and pre-measured the silver, you can go directly from the rinsing stage to the silver application. When doing multiple small pieces, clean them all one at a time and submerge them in a tub of water to await tinning and silver. With the excess water drained off your panel and replaced to its horizontal position, take the three measured cups of solution and rapidly pour the GREEN into the BLUE, then the RED into that mix. Pour the combined solutions back and forth between two cups to thoroughly mix them, and in a circular motion, pour the chemicals onto the glass surface. A good practice on larger panels is to first pour a small amount of the solution onto the surface, swill around a bit and pour off. This rinses any remaining water and greatly reduces the chance of spotting. Right afterwards; pour the rest of the solution onto the surface. Although you have positively leveled the panel at the onset, you should occasionally rock the panel left to right, and to and fro, to ensure complete coverage. Re-adjust your wedges if necessary.
You will almost immediately see a silver deposit form on the surface. It normally takes about 5 minutes, give or take, to achieve an acceptable thickness, yet it won't hurt to let the solutions stand until it begins to cloud up. At that point, there is no longer any silver in suspension. Pour off the spent liquid, and if you have dammed up the area, remove the glue bead now. It will very easily come off the surface when wet.
Now thoroughly rinse with tap water followed with distilled. You may blow dry if you wish, otherwise stand the panel up vertically, lean it against a stable backdrop, and let it drip dry. You will know when to proceed with the backing up when there are no longer appears any dull area in the silvered finish.
When dry, and your piece is to be left a solid mirror, use a soft brush to apply an even coating of backing paint. A water and acid resistant material must be used to guarantee any degree of longevity. Also it must not contain any traces of sulfur, which will in turn chemically tarnish your silver. Either orange shellac or asphaltum is traditionally used, with asphaltum our favorite. For selective backing, as in ornamentation, lettering, etc., we recommend using gold leaf back-up enamel or asphaltum as both works well in a brush. Once the backing material is dry, you can saturate the unwanted silver deposits, both front and back, with silver strip. Swabbing lightly with the strip and a paper towel or cotton wad will remove all unprotected silver. Follow up with a thorough tap water rinsing and wipe dry. In ornamental sign work when the backup is done with asphaltum, and only color is then to be applied to the open areas, give the panel a light wet coat of clear shellac to prevent the asphaltum from re-dissolving and mixing in with your color.
RESILVERING OLD MIRRORS
Using a good "water wash" industrial paint stripper and following their instructions, remove the backing paint from the mirror. Use a square of wood or plastic to scrape off the softened coating. Avoid "metal" putty knives or razor blades because "they will" scratch the glass. Even the faintest marks, unseen at first, will show up noticeably when silvered. When completely free of backing paint, swab silver strip or dilute nitric acid (the latter being faster only), to eliminate the exposed silver. Rinse well with soap and water and proceed with normal silvering.
PRECAUTIONS IN SILVERING MIRRORS (an excerpt)
The person who tries the job of silvering for the first time should not expect perfect results. There are too many chances for mistakes and too much depends on experience and judgment. Consequently, one should not tackle the silvering of a large fine mirror without first experimenting with less important pieces. In order to obtain any degree of success in the work, however, one must have an appreciation of the meaning of cleanliness in the sense it is here used. Anyone who has successfully applied a fine enameled finish and has solved the problem of eliminating dirt from the painted surface, has probably gone a long way toward acquiring the ability to silver a mirror and keep dirt away.
Another phase of the problem, and one in which the majority of beginners probably fall short, is having the surface of the glass perfectly clean. The surface should not be touched directly with the fingers after it has been cleaned, for this is likely to place a film on the surface which will make it immune from the action of the silvering solution.
An orderly method of procedure, planned out in advance,
will help one materially to carry the work through in a scientific and
successful manner. While it is necessary to work without interruption
after starting the process, the old adage of, "Haste makes waste"
is applicable to the entire performance, and steady thoughtful procedure
is in the long run better than the haste that will cause one to ruin the
work after it's three fourths done.