Miscellaneous Printing Processes 
THE PowpeEr Process.—This process is based on the fact 
that colloids lose their tackiness on exposure to light in 
contact with a bichromate. It is rarely used for paper prints, 
and its chief application has been for the preparation of re- 
versed and duplicate negatives for photo-mechanical work, 
or for making ceramic enamels. For the latter process the 
image was produced on collodionised glass to facilitate strip- 
ping, and the image transferred to the enamel plaques. 
The following are typical formule: 
Dextrine 40g 307 gr. 
White sugar 50 g 384 er. 
Ammonium bichromate 20 g 154 gr. 
Water 1000 ccm 16 oz. 
Glycerine 20 to 80 drops 10 to 40 drops 
Or: 
Gum arabic 20 g 154 gr. 
White sugar 252 192 gr. 
Ammonium bichromate 20 g 154 gr. 
Alcohol 50 ccm 34 OZ. 
Water 1000 ccm 16 oz. 
The alcohol should be added after all the other ingredients 
are dissolved. Or: 
Dextrine 48 ¢ 368 gr. 
Grape sugar 48 g 368 gr. 
Potassium bichromate 48 g 368 gr. 
Water 1000 ccm 16 oz. 
Or (Miethe) : 
Gelatine 5.8¢ 44.5 gr. 
Rock sugar candy 194¢ 30z2., 177 gr. 
314 
