CHEMISTRY of PHOTOGRAPHY

@CSU Stanislaus

CHEM 2502 Chemistry of Photography Laboratory

Section 2 -- Stop Bath and Fixer

 The purposes of these experiments are to illustrate the nature of the role of the fixer and stop bath. This is achieved by comparing contact prints which are made with and without using, either, fixer or stop bath.

 Experiment 1: The Stop Bath

Step 1 Prepare 100 mL of developer using the same formulation you used in Section 1, Experiment 5. Prepare also, 100 mL each of stop bath and fixer according to the formulation of Section 1, Experiment 2 if there is none already prepared for you.

 Step 2 Expose and develop a contact print. Dip it halfway into the stop bath for 60 seconds. Then put the print into the fixer for 5 minutes. Wash the print for 5 minutes.

 Step 3 Is there any difference visible on the print? What has omission of the stop bath step done to the print? Write the relevant chemical reactions.

Experiment 2: The Fixer

 Step 1 Expose two more prints. Develop both for the same length of time and then place each in the stop bath for 60 sec. Wash one print for 5 min. without fixing. Fix the second print for 5 min. and then wash.

 Step 2 Is there any difference between the two prints immediately after washing? Do differences appear greater after some time has passed? Why or why not? Shine a bright light on the prints. What happens? What has the fixer done? Write the chemical reaction for the action of the fixer.

 j byrd
jim@chem.csustan.edu

 m perona
mike@chem.csustan.edu