SCIOPTICON MANUAL. 71 



THE COLLODIO-CHXORIDE PROCESS. 



(From Humphrey's Journal.) 



The following formula is not only used for opal pic- 

 tures, but to some extent for transparencies also. 



1. Take the whites of two eggs and two ounces of 

 water, beat well to a froth, and let it settle for two hours 

 and pour off the clear solution. 



2. Coat your white plate with this solution (as you 

 would with collodion), and set away to dry. "When 

 dry take in your dark-room and coat the plate with 

 the " opal solution," which is made thus: 



Plain collodion 8 oz. (thinner than you would use for 

 iodizing), then dissolve in as little water as possible 60 

 grains nitrate of silver, and add this to the collodion and 

 shake well. Then dissolve 16 grains of strontium in as 

 little water as possible, and add this to the collodion and 

 shake well. Then dissolve 10 grains citric acid in as 

 little water as possible, and add to the collodion. Shake 

 well, and you have the opal solution. 



"When dry, put your negative in the printing-frame, 

 lay the opal-prepared plate on the negative, and print 

 from 10 to 15 minutes in the sun, and print much darker 

 than you would a photograph. 



Tone and fix as you would a photograph, only you 

 need not wash before toning and wash but little before 

 fixing. The "opals" tone in one-tenth the time of a 

 photograph. 



Keep the opal preparation in a dark-room. Have your 

 toning bath a little alkaline, and not as strong as for 

 toning photographs. 



