As a rule the surface of this is very greasy, and it is advisable to gently rub it over with a pad of cottonwool dipped in weak solution of ammonia till it no longer appears greasy. The best method to sensitize is to use a gelatino-chloride emulsion, or the following is simpler:

Ammonia chloride 100 grs. 20 grs.

Gelatine 30 grs. 6 rs.

Water 10 ozs. 1,000 c. c.

Soak the gelatine for half an hour, then melt in a water bath and add the chloride. Keep at a temperature of about 100° F., and then with a varnish mop coat the canvas with an even and fairly thick coating. Keep the canvas level, and allow to set and dry. When dry use a broad, flat brush and paint fairly thickly with

Silver nitrate 50 grs. 100 g. Water 1 oz. 1,000 c. c. dissolve and add Liquid ammonia fort .880 till the precipitate first formed is redissolved. Brush this evenly over the surface and dry, and it is ready for printing on; but when sensitized it will not keep more than 36 hours. - Photo-American.