Paul Raphaelson has formulated and copyrighted GPQ liquid concentrate film developer. GPQ is a Glycin- phenidone-hydroquinone formula for T-Max 100 4x5 sheet film. The short development times recommended, 5 minutes, at 1:9 dilution minimizes grain. The relatively high concentration of developing agents, particularly glycin, seem to improve the tonal seperation in the shadows and highlights. The low solvent levels also seem to improve the tonal qualities. The chemicals are used to prepare a stock solution, which is diluted 1:9 or 1:14 to obtain the working solution. The shelf life of the stock solution is about 6 months. The working solution is used once and then discarded.
STOCK SOLUTION
| Chemical | Amount | Units |
|---|---|---|
| Distilled Water (55°C) | 600 | ml |
| Sodium Sulfite | 50 | g |
| Sodium Carbonate | 26 | g |
| Diethylene Glycol | 100 | ml |
| Hydroquinone | 20 | g |
| Phenidone | 2 | g |
| Glycin | 30 | g |
| Distilled water to make | 1000 | ml |
MIXING THE STOCK SOLUTION
Dissolve the order shown. Filter after cooling to remove any insoluble
particles. The stock solution color will vary depending on the nature of
the glycin used. Store in an amber glass bottle.
USAGE
Dilute 1:9 and develop for 5 minutes for normal contrast.
Dilute 1:14 for N-1 compensating contrast development.
Dilute 1:19 for N-? results and pyrocatechin-like contrast.
Dilute 1:6 for N+ contrast and a more brilliant, straight scale.
NOTES
The contrast may be adjusted by varying the amount of sodium cabonate in
the stock solution. You may consider adding a dilute sodium carbonate solution
to the working solution if increased contrast is required.
The GPQ Liquid Concentrate formula, the instructions for use, and the name GPQ are copyrights of Paul Raphaelson, 1996.
REFERENCE
GPQ Liquid Concentrate, Paul Raphaelson