OK, I'm in my papers getting back up to speed on these.
Hardeners were mostly used for the Stop and Fixing stages to prevent the negative from getting damaged while in storage.
There were some pre-hardeners but these used formaldehyde in their solution... not really something we want to play with.
Then there are tropical developers. I'm currently looking for one that would be easy to make with as few components as possible.
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Kodak D-91
Kodelon Tropical Developer
SOLUTION
Water (about 125°F/52°C) 24 ounces 750 cc
Kodelon 100 grains 7 grams
Sodium Sulphite, desiccated 1 oz. 290 grains 50 grams
Sodium Carbonate, desiccated 1 oz. 290 grains 50 grams
Water to make 32 ounces 1 liter
Dissolve the chemicals in the order given.
Average time of development, 7 to 9 minutes at 65°F/18°C and 2 to 3 minutes at 90°F/ 32°C in fresh developer according to the contrast desired. Rinse, harden, fix, and wash as recommended for Formula DK 15
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Agfa Chrome Alum Hardening Bath
This bath may be used instead of a regular acetic acid stop-bath to give additional hardening to film. It is particularly desirable in hot weather, for tropical development, and for negatives which have to be enlarged wet.
SOLUTION
Potassium Chrome Alum 30 g
Water 1 liter
Films should be agitated thoroughly when immersed in the solution. Maximum hardening will be obtained with about 3 minutes treatment.
Solution should be used fresh as it does not keep well. Formation of a greenish sludge is an indication that the solution should be replaced by a fresh bath.
If the chrome alum used is such that a sludge is formed when the bath is first used, an addition of 1ml of concentrated Sulphuric Acid per liter of solution can be made to overcome this condition.
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Though I was reading a formula by Cramer Plates and in the instructions they say their developer is for use in places where no ice is available...
In this formula they use a pre-hardening bath made using Formalin (which is a 40% formaldehyde solution) that gets diluted 1 part folmalin to 60 parts water. Interesting but I think anybody should avoid formaldehyde as it's really nasty stuff.
I'll keep on looking...