4 PHOTOGRAPHIC FACTS AND FORMULAS 
design, will when viewed in the usual manner give the impres- 
sion of the relief of the original. 
OBJECTS UNDER GLass.—If it is desired to show the glass 
cover, give about one fourth of the whole exposure to the 
object with the glass in position; then remove the glass, and 
complete the exposure. 
To BLacken Woop.—Use: 
Borax 62.5 ¢ 1 oz. 
Glycerine 62.5 ccm 1 oz. 
Shellac 125 ¢ 2 OZ. 
Water 1000 ccm 16 oz. 
Boil until completely dissolved and add water to make up the 
original bulk, then add nigrosine WS, 125 g or 2 oz., stir 
until thoroughly dissolved, and paint the wood two or three 
times. ‘This is not as satisfactory as the following, in which 
the aniline black is chemically formed in the wood: 
Cupric chloride 70g 538 gr. 
Potassium bichromate 70g 538 gr. 
Hot water 1000 ccm 16 oz. 
The wood should be freed from grease, then painted with this 
solution and allowed to dry well, then painted with: 
Aniline hydrochloride 140 g 2% oz. 
Water 1000 ccm 16 oz. 
Allow to dry, wipe off any yellow powder that forms, and 
repaint with these solutions until black enough. As a rule, 
two coats are sufficient, as the colour deepens in a day or two. 
Then rub well with boiled linseed oil and leave to dry. 
To BLackeNn Brass.—Use: 
Copper nitrate 208 g 200 gr. 
Water 500 ccm loz 
Dissolve and add the following solution: 
Silver nitrate 208 g 200 gr. 
Water 500 ccm 1 oz. 
