|CHEMISTRY of PHOTOGRAPHY||@CSU Stanislaus|
CHEM 2502 Chemistry of Photography Laboratory
Section 1 -- The Components of a Developer
In this Section of the laboratory, the role of each of the chemicals in a developer will be investigated by preparing a developer in a stepwise fashion. As each substance is included or deleted from the developer, the contact prints which are obtained will be used to help identify the role played by that substance. Write your own purpose for each of these experiments.
There are 5 experiments that are incorporated in Section 1. In Experiment 1the set of optimum, or best, conditions for making a black and white contact print, is determined experimentally. In Experiment 2, a developer is prepared which contains only water and the compound, metol, to determine if this is sufficient for development. Experiment 3 is designed to determine if a second compound, sodium carbonate (Na2CO3H2O), improves the developer and, if so, what changes occur. In Experiment 4 another compound is included. This compound is sodium sulfite, (Na2SO3). The purpose in now to determine the role played by soduim sulfite in a developer. Finally, in Experiment 5, sodium bromide (NaBr) is included to determine its effect on the development process.
Experiment 1 -- Determining the Optimum Conditions
Step 1 Obtain several sheets of photographic paper. Caution: this paper is, of course, very sensitive to light. Be certain it never sees the "light of day."
Step 2 Place approximately 100 mL each of the prepared developer, stop bath, fixer and deionized water into 4 different 400 mL beakers; label each beaker. [Note: developer and stop bath can be disposed of down the drain. Fixer must be placed in the used fixer container because it contains silver.)
Step 3 Set up the exposing light as shown in the figure.
Step 4 Using only red safety lights, remove a piece of photographic paper from its storage space and place it directly under the light with emulsion side up. Place the negative on top of the paper and a piece of glass on top of the negative.
Step 5 Turn on the light for 15 seconds to expose the paper.
Step 6 Develop the print (still in safety light) by placing it in the beaker containing the developer for 30 seconds (caution: use tongs), then the stop bath for 5 seconds, the fixer for 5 minutes and the deionized water wash for 5 minutes. While the paper is in the developer and stop bath, be certain that you agitate it by holding it with tongs and swishing it about in the solution. Place the print on a paper towel to dry. Record the temperature of the developer, the Variac setting, and the exposure and developer times.
Step 7 Try to improve the print. If it is too dark, reduce the exposure or the developing time. The exposure can be reduced by reducing the exposure time, raising the bulb or reducing the setting on the Variac. If the print is too light, the opposite remedies should be applied. Be certain to keep an accurate record of your conditions for each experiment. Your goal here is to find the conditions for the best print possible. You will use these conditions as a starting point in the subsequent sections for your developer.
Experiment 2 -- Metol, The Reducing Agent
The purpose of this experiment is to determine if a solution containing only metol can develop a black and white print.
Step 1 Prepare a developer by dissolving 0.60 g of metol in deionized water and dilute to 100 mL. Pour into your 400 mL developing beaker.
Step 2 Prepare a stop bath, if necessary, by diluting 5 ml of 28% acetic acid to 100 mL with deionized water. Pour the solution into your stop bath beaker.
Step 3 Prepare a fixer, if necessary, by dissolving 1.0 g of sodium sulfite, Na2SO3, 2.5 g sodium bisulfite, NaHSO3, and 24.0 g of sodium thiosulfate, Na2S2O35H2O in water and dilute to 100 mL. Pour this into your fixer beaker.
Step 4 Prepare a wash beaker with deionized water.
Step 5 Expose a piece of paper with the negative on top of it in exactly the same way as in Experiment 1. Develop the contact print also in the same way. Record the conditions and the results. Is there any reduction of silver ion to metallic silver? Try to improve the print by changing the conditions. Record the results. Note any color changes in the developer solution with time.
Experiment 3 - Sodium Carbonate, The Activator
Prepare another developer by dissolving 0.60 g of metol and 2.00
g of sodium carbonate
(Na2CO3H2O), in water and diluting it to 100 mL with deionized water.
Step 2 Prepare a new stop bath and a new fixer or use the ones that you used in Experiment 2.
Step 3 Expose and develop the contact print using the optimum conditions of Experiment 1. Has there been any reduction of silver ion to metallic silver? Try to improve the print by increasing the exposure time or brightness. Try to increase the developer time. Be certain to record all of your observations, conditions and results. Is this developer as good at reducing the silver as the developer of Experiment 1?
Experiment 4 -- Sodium Sulfite, The Preservative
Step 1 Prepare a new developer by dissolving, in this order, 1.90 g of sodium sulfite (Na2SO3), 0.60 g of metol and 2.00 g of sodium carbonate, Na2CO3H2O, in deionized water and diluting to 100 mL.
Step 2 Expose a contact print in the same manner as in Experiment 1. Develop the print also as outlined in Experiment 1. Record the results.
Change conditions to attempt to improve the print. Is this possible? What effect does the sodium sulfite have? Explain the effect using chemical equations.
Experiment 5 -- Sodium Bromide, the Restrainer
Step 1 Prepare yet another developer by dissolving 2.00 g Na2SO3, 0.25 g sodium bromide (NaBr), 0.60 g metol, and 2.00 g of Na2CO3H2O in distilled water and dilute to 100 ml. Be sure to dissolve these chemicals in the order listed.
Step 2 Expose and develop a contact print again according to your optimum conditions of Experiment 1. Record your results. Try to improve the print.
Step 3 How does this print compare with that of Experiment 1? Experiment 4? What has been the effect of the NaBr? Explain briefly how the bromide ion (Br-) functions.