PHOTOGRAPHIC PROCESSES. 93 



add any ammonia, use a few drops of nitric acid in- 

 stead. 



Another way Eub the glass over with the follow- 

 ing solution : Silicate of soda, loz. ; water, 30oz. ; 

 rub dry with tissue paper. 



Another way is to use the glass without any 

 substratum. This is less trouble and just as good. 

 Do not polish, simply rub off dirt with dry cloth. If 

 the emulsion does not flow readily, on account of 

 plates being too ccld, you can assist the emulsion to 

 the edges with a glass rod or your finger. If air 

 bubbles get on the plate, break them with pieces of 

 filtering paper, The greatest cause of failure is too 

 much light in flowing and drying the plates. Also 

 dust is a great enemy. Fog, if not from light, comes 

 from free silver left in the emulsion. An emulsion 

 of this kind can be made all right by putting it again 

 into the brine, leavirg for a few hours, and washing 

 as before. The temperature of the brine should be 

 CO or 70. I would advise you to make all your 

 plates in spring for summer use, and in the fall for 

 winter use, as it is much more pleasant. Do not have 

 the flowing room over 80, 60 to 70 is better. Plates 

 that have been exposed to light and not developed, 

 can be soaked in a solution of bichromate of potash and 

 washed and dried, and they are as good as before ex- 

 posure. Be sure and keep plates dry. Dampness 

 is a great enemy to the dry plate. Plates that take 

 along time to dry are apt to frill. If you wish to make 

 a more intense negative than this formula gives, use 

 same amount of gelatine and less silver ; if you want 



