mixing rodinal from scratch

[noahfactor]

I made a stupid mistake with the rodinal kit from photographer's formulary. I

was unclear with the directions (actually the directions are unclear) and I

did not put in enough potassium hydroxide to get rid of the precipitate. I

only put in the amount that the instructions said and (not thinking) threw out

the rest. Im currently in south korea and cant find premixed rodinal, so my

question is are there any house hold chemicals i could use to replace the

potassium hydroxide (would a weak base work)?

[john_stockdale2]

Just a guess: the only readily available chemical that might be suitable is sodium hydroxide (caustic soda). Sodium compounds are chemically similar to potassium ones, but are less soluble, and that might have an adverse effect in this case. If you only need a small amount, it's worth a try.

 

Potassium compounds are often used to make highly concentrated developers because of their high solubility.

[big toys are better]

The formulary would be best choice to answer the question, and it may also be in a reference manual like the cookbook, but from my chemistry background I suspect that NaOH will probably work just fine although its saturation point may be weaker than KOH. Either way, the final developer will probably work fine as well but may need a bit of calibration.

 

BTW-- Both KOH and NaOH are VERY STRONG BASES! This means they are dangerous, and also that a weak base will not work in their place since you are looking to establish an equilibrium which would be weakened by a weak base (increase the final volume way too much). I would also thing that KOH can be obtained at a local chemical supply house.

[chris_waller]

Noah,

 

Anchell & Troops 'Film Developing Cookbook' gives a Rodinal formula which uses sodium hydroxide in the second solution at a rate of 200 gm in a total of 400 ml of solution.

 

Rodinal needs a very strong alkali to activate it so a weak base such as sodium carbonate would not work. Sodium hydroxide is freely available in the UK for clearing drains, though I don't know how Koreans clear their drains. It shouldn't be difficult to get hold of.

[noahfactor]

Thanks a lot for your responses. I was actually able to get KOH from the chemistry department at the school i work for. However, after i finished mixing the rodinal at the school i was informed by the vice principle that i cannot take any school chemicals outside the school, even the small amount of KOH i mixed into my existing half-rodinal solution. so, thats the end of that. i guess ill just have to order more. thanks for all your help.

[pete_andrews10]

You can use Sodium Hydroxide to make up Rodinal with no problem. In fact you need less NaOH than KOH, in the proportion of 5 parts NaOH to every 7 parts KOH (molecular weights are 40 and 56 respectively).

 

As a matter of fact; Rodinal can be made up entirely with Sodium salts, including the substitution of Potassium Sulphite by Sodium Sulphite. There is an issue with the sodium salts having a lower solubility, but this is only a problem if the solution is stored at a low temperature (under 10 Celcius). Some crystallisation occurs in the bottom of the bottle in these circumstances, but the crystals will re-dissolve if the temperature is raised again.

 

BTW Noah. Have you tried making up Para-Rodinal?

 

Para-aminophenol, the active ingredient in Rodinal, can be made from mixing Paracetamol (Acetominophen), the common painkiller, with Sodium or Potassium Hydroxide. Results are pretty much identical with genuine Rodinal. Equally good, or bad, depending on your view of Rodinal.

[noahfactor]

Really? No, i havent tried mixing that. Could you tell me the exact formula, i.e., how much acetomenophen and how much sodium or potassium hydroxide? Im very intrigued.

[pete_andrews10]

I haven't got the formula in my head, but the only critical thing is the amount of Sodium hydroxide (potassium hydroxide would be better, but I can't get supplies of that easily). The idea was to make a developer entirely from pharmacy and/or hardware store supplies.

 

7gms of Paracetamol neutralised with caustic soda/potash gives the equivalent of 5gms para-aminophenol + some sodium/potassium Acetate, which is photographically inert. For the preservative, I use sodium metabisulphite, which I can buy from a home-brew suppliers. Again it needs mixing with sodium or potassium hydroxide to convert it to sodium or potassium sulphite.

 

I don't bother with a restrainer at all, since none of the old published PAP-caustic formulae include one, and most modern films include an organic restrainer in the emulsion anyway.

 

So, all you need are three ingredients, 14 x 500mg paracetamol tablets, some caustic soda or potash, and about 25gms of sodium metabisulphite, to make 125ml of Rodinal substitute.

 

I'll dig the exact recipe out and post it later. Or there are previous postings on the subject, some of which give the quantities needed, and method of making-up.

[patrick_gainer]

It doesn't have to be metabisulfite. Use the sulfite and you need less caustic soda or potash.

 

If you can get p-aminophenol base, this works:

 

400 ml water.

85 g sodium sulfite.

40 g p-aminophenol.

Mix these and then add 13.8 g sodium hydroxide or 19.2 g potassium hydroxide. Some precipitate will remain. Keep it in your stock as a sort of preservative against aerial oxidation.

 

If you have to use acetaminophen, be careful not to use too much hydroxide to remove the acetate.