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USEFUL FACTS AND FORMULAE 589
FERRICYANIDE (FARMER'S) REDUCER.
Reduces the shadows more than the high-lights. Must be freshly prepared as it deteriorates rapidly.
Add to the desired quantity of fresh hypo solution enough of a saturated solution of Potassium Ferricyanide to make it lemon colored. If the color is too deep, verging on orange, reduction will be too rapid to be controlled. When reduction has proceeded far enough, wash the film quickly to prevent further action.
HANDY EMERGENCY WEIGHTS
Dime 40 grs.
Cent 50 grs.
Nickel 80 grs.
Quarter-Dollar 1 00 grs.
Half-Dollar 200 grs.
Dollar 400 g rs.
FLAT BLACK VARNISH FOR BLACKING INSIDE OF CAMERA, ETC.
Alcohol 8 ounces.
Lamp Black 2 ounces.
Shellac 1 ounce.
Dissolve shellac in alcohol, then add lamp black, and mix thoroughly.
FLAT BLACK FOR METALLIC PARTS— SHUTTERS, DIAPHRAGMS, Etc
Nitric Acid 4 ounces.
Copper Wire *4 ounce.
Dissolve the copper wire in the nitric acid and then add slowly 1 J4 ounces of water.
The parts to be blackened must be thoroughly cleaned, then heated and immersed in the acid bath after which they are taken out and brushed off or until the article shows a rich blue-black.
INK FOR WRITING ON GLASS
WHITE: Mix 1 part Chinese White (water-color pigment) or Barium Sulphate with 3 or 4 parts Sodium Silicate Solution (water glass) . The sodium silicate solution should have the consistency of glycerin.
BLACK: Mix 1 part liquid Chinese Ink (or Higgins "Eternal" or other carbon ink) with 2 parts Sodium Silicate Solution.
Apply with ordinary steel pen. Ink will dry in 15 minutes. It is waterproof, but may be removed by scraping with a knife.
DEAD BLACK FOR WOOD
Borax 30 grs 8 grams.
Glycerin 30 minims 8 cc.
Shellac 60 grs 16 grams.
Water 8 ounces 1000 cc.
Boil till dissolved, and add:
Nigrosine, W. S. 60 grs 16 grams.
Or paint the wood first with:
Cupric Chloride 75 grs 75 grams.
Potassium Bichromate 75 ounces 75 grams.
Water 2|4 grs 1000 cc.
As soon as the surface dries, apply:
Aniline Hydrochlorate 150 grs 150 grams.
Water 2J4 ounces 1000 cc.
Wipe off any yellow powder that forms. Repeat the process until black enough. Then rub over with boiled linseed oil.
WATERPROOFING WOOD
Asphalt 4 ounces 400 grams.
Pure Rubber 30 grs 6 grams.
Mineral Naphtha 10 ounces 1000 cc.
Apply with a stiff brush. Give three successive coats, allowing each to dry thoroughly. The vapor from this solution is highly inflammable.