Friday, June 4, 2010

More concentrated stock solution?

To make a more concentrated stock solution of GSD-10 would require only substituting potassium carbonate for sodium carbonate, and reducing the ratio of sodium sulfite to glycin to around 1:1. The more concentrated version would look something like:

Distilled water: 50ml
Sodium sulfite: 12g
Glycin: 10g
Potassium carbonate: 75g
Distilled water to 100ml

This concentrate would be diluted 1:50 for intermittent or rotary processing, and 1:100-1:200 for stand development.

I would expect to see an increase in the appearance of both grain and sharpness. Personally, I like the way GSD-10 balances of grain and sharpness, and so I would consider this concentrated version a compromise, especially for 35mm work.

Another option would be to double the concentration of GSD-10 by retaining the formula as-is, and simply making it up in 1/2 the water. This version would be:

Distilled water: 500ml
Sodium sulfite 100g
Glycin: 20g
Sodium carbonate: 150g
Distilled water to 1 liter

Dilute 1:10 for intermittent or rotary processing, and 1:20-1:40 for stand development.

I like this option better, since it would still be the developer I know and love, but I will try both options and compare them before coming to any conclusions. If anyone decides to experiment with these, or any other variations, I'd love to know about it. Please contact me at:

with any comments, questions or suggestions, and I'm always very happy to see images made with my developers.


kyle said...

Would the more concentrated stocks have longer life?

jdef said...

Theoretically, yes; more concentrated solutions are more stable, and so have longer shelf lives. The concentration of a compound solution, like a developer, is usually determined by the solubility of one or more constituents. In the case of GSD-10, sodium sulfite is the limiting constituent.

jdef said...

I'v been using the 2X concentrate, and it works very well- just like the less concentrated version. If you want to mix your GSD-10 this way, you'll have to heat 2/3 the final volume of water in order to dissolve the sulfite; 100g of sulfite won't dissolve in 666ml of water at room temperature. Make sure all the sulfite is completely dissolved before adding the carbonate. The carbonate will heat up the solution a little through an exothermic reaction, so add it slowly, and make sure it's all dissolved before adding the glycin. When all the chemicals are completely dissolved, top up to final volume with cold water. Mixed this way, the stock should be diluted 1:10 for rotary development, and 1:20-1:60 for Low Frequency Agitation, or stand development.

jdef said...

I've changed the official formula to this 2X concentrated version.