Adding KOH into glycol instead of water

Fatih Ayoglu · Jun 12, 2025

Hi all,

Is it possible to add KOH into glycol instead of water? I have a formula which requires 1.4gm KOH per litre however I dont want to measure this every time so I'd like to have a 10% solution of glycol to keep it stable and measure 14ml each time. In fact I'd like to mix KOH into 2% phenidone solution

(To my understanding, when KOH added into water, it lasts about 6 months or so)

Best wishes,
Fatih

koraks · Jun 12, 2025

Potassium hydroxide is stable in water so you can just use that for your stock solution. I doubt it dissolves in glycol anyway.

koraks · Jun 12, 2025

Fatih Ayoglu said:
In fact I'd like to mix KOH into 2% phenidone solution

This will not keep unless you add an antioxidant; the phenidone will die. You'll be reinventing some kind of developer when all is said and done.
Maybe it's easier if you just explain what you're trying to achieve.

Fatih Ayoglu · Jun 12, 2025

koraks said:
This will not keep unless you add an antioxidant; the phenidone will die. You'll be reinventing some kind of developer when all is said and done.
Maybe it's easier if you just explain what you're trying to achieve.

No, Phenidone is in glycol so it will keep well. I am using Muir SoftShot to develop extremely low contrast masks with Arista Ortho and FP4. The entire formula works well and I get good results. However it has many parts which I'd like to mix into glycol to keep it like a syrup and mix with water when I need it.
Per litre working solution, I need 2g phenidone, 0.4g VitC, 1.4g KOH and 10g Sodium Sulfite with 15ml BZT (2%)

So my idea was prepare a litre syrup with glycol, add 20g Phenidone, 100g Sodium Sulfite 4g VitC and 14g KOH. I can take 100ml of this and mix with water to make working solution

Yezishu · Jun 12, 2025

Sodium sulfite does not dissolve easily in ethylene glycol, and phenidone is prone to oxidation under alkaline conditions.
I suggest to consider preparing two separate solutions: one with phenidone, vitamin C, and ethylene glycol; the other with sodium sulfite, potassium hydroxide, and water. Mix them together in a ratio, such as 1:1:10.

koraks · Jun 12, 2025

Fatih Ayoglu said:
So my idea was prepare a litre syrup with glycol, add 20g Phenidone, 100g Sodium Sulfite 4g VitC and 14g KOH. I can take 100ml of this and mix with water to make working solution

The fact that you can't buy this should be taken as a hint as to the fundamental problems with this approach. Kodak wouldn't have bothered with things like powder in bags, encapsulation technology etc if this would work.

You can make a couple of concentrates that would sort of work. There's a few threads on the forum about vitamin C developers and attempts to make concentrates out of them. A single concentrate is not going to happen I'm afraid.

Yezishu said:
the other with sodium sulfite, potassium hydroxide, and water.

The sulfite will oxidize into sulfate; it'll last for some time but not very long. Hard to tell how long you can stretch it.

Fatih Ayoglu · Jun 12, 2025

So if Phenidone and VitC can stay together in Glycol without an issue, at least that will solve part of my problem. BZT stays in water well. Sodium sulfite is large enough I can measure. As long as KOH in water can stay for couple of months, I think I can live with it

Fatih Ayoglu · Jun 12, 2025

Btw I just need to use this until I finish my phenidone stock, then I’ll move HC110 dilution with BZT for similar work.

koraks · Jun 12, 2025

Fatih Ayoglu said:
BZT stays in water well.

Yes, although it dissolves easier in ethanol. Which of course has the disadvantage that it tends to evaporate, but in a properly sealed bottle, this is not a problem.

Fatih Ayoglu said:
As long as KOH in water can stay for couple of months, I think I can live with it

No worries there; it's stable. I think people who argue it's not stable are thinking of uptake of CO2 from the air, which simply put will eat up the KOH over time. But it takes a long time, and just capping the bottle stops the process, so it's not a practical concern.

Yezishu · Jun 12, 2025

Kodak’s solution for providing sulfite (and alkalinity) in concentrates is an alkanolamine solution of a sulfur dioxide–triethanolamine adduct. It makes sense, but handling sulfur dioxide gas is not practical for personal mixing. I’ve considered whether heating a mixture of sodium bisulfite and alkanolamine, then filtering it, could produce a similar compound—but this is just a thought.

The role of potassium hydroxide here is simply to provide the necessary pH. If you have calculated or measured the required amount, you can substitute it with borax or another alkali (such as sodium carbonate, or even sodium sulfite itself). These can be mixed with sodium sulfite as a powder and packaged in single-use sachets.

Fatih Ayoglu · Jun 12, 2025

koraks said:
No worries there; it's stable. I think people who argue it's not stable are thinking of uptake of CO2 from the air, which simply put will eat up the KOH over time. But it takes a long time, and just capping the bottle stops the process, so it's not a practical concern.

Aha, that's good. I always thought it goes bad quickly. I can prepare a solution and keep it in a tightly capped bottle. Thank you

koraks · Jun 12, 2025

That'll work fine. I've kept bottles of 5-10% NaOH and KOH around for well over a year. They don't seem to change, other than that there's always a little precipitation, so the bottle tends to look kind of ugly.

lamerko · Jun 13, 2025

Here they sell a solution of NaOH and KOH - about 30% as household chemicals - for unclogging drains, making soap, etc. I spoke to a local manufacturer of one of these products - he claims that this is a pure solution, without any impurities. They give it a shelf life of two years - it will probably last longer, but like Himalayan salt, they should indicate some period. After about a year of storage and a dozen or so opening of the HDPE bottle, there is no sediment inside, but it really gets ugly around the cap.

Fatih Ayoglu · Jun 13, 2025

Thnak you that is great. I can prepare 3 separate solutions, one for BZT, one for Phenindione/AA and one for KOH (probably even a weaker one to use up faster). I can always add Sulfite later one (which is a good thing as it slows down the oxidisation)

Thanks a lot all

koraks · Jun 13, 2025

Fatih Ayoglu said:
I can prepare 3 separate solutions, one for BZT, one for Phenindione/AA and one for KOH (probably even a weaker one to use up faster).

I'd recommend making the phenidone a separate solution without the ascorbic acid. That way you can use it for other purposes as well. A 1% or 2% solution generally works well but since you need quite a lot, you could try and make a stronger solution so you'll need less of it.
You could make a separate ascorbic acid solution in glycol; something like a 5% solution should be feasible. I understand from online search that up to 9% should also work, but will take more effort to get it to dissolve.
The KOH can be made as a regular watery 10% solution in plain water.
The sodium sulfite can be weighed out when mixing the developer. Only mix as much developer as you'll use in a single session; I do not expect it will keep very well.

The developer is Muir SoftShot and it's recommended by Ctein in his Post Exposure book for making contrast masks for color work (pp.103-105). The reason for the odd composition is that this developer is tailored to yield neutral density negatives on TMAX100 when developed to a very low gamma. Note that there's no guarantee it'll do the same on other types of film, although it may (should) do better than other developers of a more normal formulation.

I trust this will settle your previous question you asked here: https://www.photrio.com/forum/threads/mixing-my-own-liquid-developer-extending-shelf-life.204741 I'll lock that thread with a link to the present one to prevent possible redundancy when someone comes across it in the future.

Fatih Ayoglu · Jun 13, 2025

Thanks a lot @koraks I'll follow your recommendation. Yes precisely you are correct. On a note for future reference;
The given solution works well with Foma100 and Ilford FP4 sheet films. I follow the same 3 mins developing time and adjust the density of the mask with exposure. It gives a very long straight curve with 0.3 du.

I also use it with Arista Ortho film for the same purpose but mix it 1:4 instead of using straight. Again using 3 mins developing time. This also gives me a straight curve mask with 0.3 du. Again I adjust the density with exposure. The benefit of this solution with Arista Ortho film is, it does give a neutral colour mask rather than brown tinted one (if the film is developed with a weak paper developer).

koraks · Jun 13, 2025

Great, thanks for sharing these baseline parameters; very useful!

Adding KOH into glycol instead of water

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