Nitric Acid Concentration in Dupont 6-T?

[tgtaylor]

Do you think that a 7% solution of nitric acid will work for Varigram toning bleach 6B-3 in the formulas for Dupont 6-T system? The Darkroom Cookbook doesn't specify a concentration and my only experience with this acid is from college chemistry lab where it was in its concentrated form: When you opened the bottle a sinuous white vapor drifted up toward the ceiling.

Thomas

[BarryS]

Concentrated nitric acid is a 68% solution--approximately ten times as concentrated as your 7% solution. I doubt the amount is that critical, but you could substitute 10x the amount of nitric acid called for, and add proportionately less water to make up the final volume. I use the 6-T toner system, but find I don't need anything beyond the 6B-1 and 6B-2 bleaches.

[tgtaylor]

Thanks Barry. The chemistry is on the way - should have it on Friday. The 7% solution should work as that is the same concentration used for the wet plate process.

Thomas