Developers in organic solvents.
Safer glycols
I found an auto supply store that had the safe propylene glycol antifreeze. It worked as well as the ethylene. Another benign solvent that works is glycerol (glycerine at the drug store), but it is very viscous, even more so than HC110 syrup.
Technical grade propylene glycol is readily available. It works, so I am sure that the additives in the antifreeze that make it green had no appreciable good or bad effect.
There are other activator solutions that you might use with A1:
1. Try 100 grams of sulfite and 2 grams of borax per liter as the "B" solution. Add 20 ml of the "A1" solution per liter just before use. This is a kind of extended life split-stock developer of the type of Paul Lewis' Mytol.
2. Use 5 grams of borax + 5 grams of sodium carbonate + 20 ml of "A1" per liter of working solution (no sulfite). Development time will be about 8 minutes at 70o F. One teaspoon each of borax and carbonate will be accurate enough due to the buffering action of the combination.
Other uses for propylene glycol.
Use propylene glycol in place of water to make the "A" solution of Pyrocat-HD. Leave out bisulfite and bromide. Heat to hasten dissolving and to drive off water. Let's call it "A2". Use the standard Pyrocat-HD "B" solution.
See
http://unblinkingeye.com/Articles/PC-HD/pc-hd.html for the standard formula and developing times for Pyrocat HD.
Alternatively, use hydroquinone in place of catechol in A2. I'll bet you didn't know that hydroquinone can be a staining developer. Hydroquinone is 1,4-dihydroxybenzene. Pyrocatechol is 1,2-dihydroxybenzene. According to theory, any developer with two or more active hydroxyl groups will be an active tanning and staining developer.
Dilute 1:1:50. Add "B" to working solution just before developing. Don't be put off by the immediate change in color. Develop 7 or 8 minutes at 70o F.
If you keep phenidone in alcohol solution, use propylene glycol instead of the alcohol. Rumors that there is no way to keep phenidone in solution are greatly exaggerated. Heat the glycol or you will have to wait a week or so for the phenidone to dissolve.
Dire and not-so-dire warnings.
If you repeat my experiments but do not have a microwave oven, put the glycol in a Pyrex pitcher, set that in a baking dish in an ordinary oven. Set the oven at 250o F.. A candy thermometer is a good investment. Check the temperature of the liquid now and then, but not with your finger. If you see steam rising from the glycol it is most likely water vapor.
Propylene glycol (1,2-propanediol) and glycerine (1,2,3-propanetriol) are non-toxic to the extent that they can be used in foods, medicines and cosmetics. Propylene glycol is poisonous to cats but not to dogs. I don't think cats will ingest it willingly. Ethylene glycol is bad stuff for everyone. Dogs and little children love it because it is sweet, but it kills them. If you use it, do so with caution. HC110 contains it and diethylene glycol as well, and many of us use HC110 without a lot of worry. Maybe we don't worry enough. If you are careful, you will not have to worry.
Single solution developers
It is possible to prepare single solution developers with excellent storage life by using an organic base as solvent and activator. The organic bases become alkaline in the presence of water. Triethanolamine (TEA for short) is an example, and it is readily obtainable without hazmat shipping charges. One problem you may have is that it freezes at about 70o F. If your darkroom is colder than that you will have the strange experience of having to thaw out iced TEA before you can pour it. The freezing point will be lowered somewhat after you dissolve the solids in it. Here are some useful formulas.
P-C-TEA
Call it whatever you want. It is a phenidone-ascorbic acid developer with TEA as activator and solvent. I can't find the grain in properly exposed HP5+ or 400TMY at less than 20 power enlargement.
You may scale up the formula to any desired amount.
100 ml of TEA
9 grams l-ascorbic acid powder (Vitamin C Powder)
0.25 grams phenidone (1/8 tsp will be close enough.)
Heat the TEA to 250o F before adding the other ingredients. It won't boil, but some steam may be given off if there is any water in the solvent mixture. Steam will be evolved when the powdered ingredients are added, which I presume to be from water produced in a reaction between the ascorbic acid and part of the TEA.
Dilute 1+50 to develop 400TMax in 9.5 minutes at 70o F.
CAT-P-TEA
The name does not refer to its appearance or its bouquet. I heard it in a British sit-com and just couldn't resist using it. This developer contains catechol and phenidone. It is a staining developer.
100 ml TEA
0.2 gram phenidone
10 grams catechol
You may use a like amount of hydroquinone in place of the catechol if you like to save money. Call that Q-P-TEA.
Heat as before. Dilute 1+50 for use. The negatives will be lower in contrast to the eye than to the printing paper, and lower in contrast to VC than to graded paper.
If you use a 1% sodium sulfite solution (10 gram/liter) to dilute the stock you will have a fine-grain non-staining developer. You can experiment with different proportions of stock, sulfite solution and water.
P-TEA
This name also does not refer to its appearance but to the fact that pyrogallol is the sole developing agent. This and D-23 are the simplest single solution developers I know of. It is the only single stock concentrate that I know of with only two ingredients.
Many fear pyrogallol. That is a healthy fear, but with reasonable care there is no need to inhale or handle the pyro while mixing or using this developer.
100 ml TEA
7 grams pyrogallol
Dilute 1 + 50 for use.
Again, the negatives will be stained. This developer will produce a strong dye image on 400TMY film. It will prove to you that Pyrogallol alone is not intrinsically a coarse-grain developer.