Rodinal (EZ , Gainer Formula) Troubleshooting
I gave making Patrick Gainer's EZ Rodinal a try after reading the forum posts here. It seemed more straightforward than the Anchell and Troop book version.
The EZ Rodinal formula is
To 400 ml water, add: 85 g anhydrous sodium sulfite. 40 g p-aminophenol base. Stir well. Add 13.8 g sodium hydroxide or 19.2 g potassium hydroxide. Add water to make 500 ml.
To a brown bottle with 400ml deionized water I added the sodium sulfite first and the p-aminophenol next, while constantly stirring with a magnetic stirbar. Not much seemed to dissolve even after 30minutes and heating to about 60 degrees. So I put in the KOH and the solution cleared quite a bit. The magnetic stirrer has went for a few hours but the solution was still quite cloudy and a lot of undissolved material is present. I would say about 2-3 tablespoons full of crystals. And it doesn't settle very readily.
Is this normal? I thought that only a few crystals were supposed to remain. Also, does this mean that I should titrate in more base until a tiny amount of precipitate is left? If so, what is the target pH of Rodinal? I would appreciate advice from people who've tried this formula out before.
Last edited by chakra; 06-12-2008 at 08:32 AM. Click to view previous post history.
The sulfite should dissolve readily. The p-aminophenol should not. If it did, it would be a sign that you had used p-aminophenol.HCl. This can be done, but will require different proportions. The hydroxide might be partly K2CO3 due to exposure to atmosphere.
The hydroxide converts p-aminophenol base to the potassium salt which is water soluble.
After I read your post, I retreated to my dungeon and made a batch of EZ-Rodinal. I had less than a teaspoon of sediment after stirring a few minutes with a soupspoon (my recently discovered automatic stirring machine). I tested it on HP5+ at 1+25 dilution according to instructions on an old Rodinal container, with proper results.
If through some accident you had used the p-aminophenol.HCl, the proper cure would be to double the amount of KOH. If the KOH is weak for one reason or another, the proper cure is again more KOH, but not so easilly determined. Perhaps the reason for the titration in older recipes was the uncertainty of purity of either or both p-aminophenol and KOH. You could not go wrong by adding more KOH to see if more of the sediment dissolves. It runs in my mind that a saturated solution of KOH will hold very little K2CO3, and will have a concentration that depends on temperature. If you make such a solution at a temperature higher than you are likely to have while working in your darkroom, and make sure it has an excess, you can use a table from the CRC Handbook of Physics and Chemistry to calculate how many ml of this solution will contain 19.2 grams of KOH at the current darkroom temperature.
You could try filtering out the precipitate and testing the clear liquid as if it were Rodinal.
Thanks so much for your reply and for testing the formula out yourself.
I bought the p-aminophenol and sodium sulfite reagents brand new from PhotoFormulary. The KOH was from a nearly full but old bottle in a research lab where I work.
I started the automatic stirrer with 400mls of water and dunked in the sulfite followed immediately by the p-aminophenol. So I am guessing that the sulfite went into solution but but the white stuff that simply would not dissolve was mostly p-aminophenol. I checked to see that the p-aminophenol bottle does not say HCL on it.
After adding the KOH (added pellets directly to the mix) things cleared but still had way too much sediment in it. So I added about 6 more grams of KOH in 2 gram steps. After the last two grams things suddenly cleared, the color went a bit pinkish and left only a tiny amount of crystals in it. I was worried about if I had added too much KOH. So I checked the pH and found it was about 12.5 (using both pH paper and a pH meter). This seemed high , but googling didn't turn up any references for rodinal's target pH which seemed a good way for getting some kind of standard.
I'll try this again tomorrow. A couple more questions
1. Does the order of adding the reagents make a difference?
2. I have old but nearly full bottles of both NaOH and KOH. Is there a reason to prefer one over the other?
3. What final pH should I be shooting for?
I'll check to see what pH I got. It will be pretty high, I'm sure. The sodium paraminophenolate is a salt of a strong bas and (I guess) a weak acid if that rule says anything about this situation. I did measure the pH of a 1:25 working solution, but forgot to write it down.
I read 11.9 in the batch of stock I just made. As I said, it behaves just as I would expect Rodinal to behave. I don't think you need to worry. Just try developing a test strip. The diffrence between 11.9 and 12.5 is not much at that level.
I think from the standpoint of protecting the p-aminophenol, it is best to ddissolve the sulfite first, then the p-aminophenol, then the KOH. I think K salts were easier to get or make for the Germans at the time of Rodinal's inception. It was interesting to me that Hurter & Driffield mentioned rodinal, with the lower case, as a developing agent. I suspect that was potassium paraminophenolate. If that is available, it would simplify things for us, would it not?
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If you want to read more on the subject of Rodinal, you might be interested in this post on rec.photo.darkroom, in which Michael Gudziniwicz discusses someone else's "home brew" made with p-aminiphenol:
You can see the whole thread by clicking on the link of the title , i.e. "My Home Brew."
Unfortunately rec.photo.darkroom isn't nearly as good as it used to be, but there are some gems there.
OK. So I redid the preparation in graduated 50ml plastic tubes with both KOH and NaOH.
To 40ml deionized water I added 8.5 gram sodium sulfite. Capped the tube and inverted until it dissolved. To this I then added 4g p-aminophenol base. That led to some kind of whitish colloidal precipitate which would not dissolve further. Next I started titrating with a ~20 molar solution of KOH. There was a very clear relation between amount of base added and how much precipitate went into solution. I titrated until there was only a pinch of precipitate left at the bottom. I had to add about 5 grams equivalent of KOH solution and the pH was 13.1.
I redid this with NaOH and it was MUCH harder to get the solution to clear. I have the tube sitting with precipitate upto about the 10ml mark and a pH of 12.8. If it doesn't clear by tomorrow I'll bring the pH upto about 13.1 so I can compare the two solutions.
The 5 gram number is almost 3 times the amount should need to add, and it makes me wonder if the bottle was mispackaged or if age of the p-aminophenol makes a difference. And I am still a bit worried that my solution clears at a higher pH.
I'll run a comparison with Tri-X in the coming week and report back.
I am also realizing that I have almost no understanding of the underlying chemistry.
Could you recommend a few photographic chemistry texts or manuscripts?
Have you read the post by Gudzinowicz in re.photo.darkroom? It is quite enlightening.
Test the water solubility of your p-aminophenol. If it is in fact the base, it should not be very soluble. The hydrochloride is more soluble than Metol.
I don't think that is the problem, though. Of course, our pH meters may not be calibrated alike, but the pH of my final solution with just a little precipitate reads less than 12.
Traditionally, the preparation of Rodinal begins with p-aminophenol.HCl in solution. Adding potassium metabisulfite does not cause it to precipitate. The first addition of hydroxide, either Na or K, removes HCl from the tail, which makes the flocculent precipitate. As more hydroxide is added, the potassium or sodium aminophenolate salt is formed, which is the final developing agent, and is quite soluble in water. If you have pure ingredients, the amount of each one required to convert all the p-aminophenol.HCl to a solution of the aminophenolate salt and NaCl or KCl can be calculated. The shelf life of the Rodinal stock is much extended if some of the p-aminophenol base is left undissolved. I do not know why, but apparently Gudzinowicz does. The amount of hydroxide required to remove the HCl from the hydrochloride is, in molecular weights, the same as the amount required to make the aminophenolate, so using the p-aminophenol base in place of the hydrochloride will require only half as much hydroxide. Last time I bought any, a pound of the base cost the same as a pound of the hydrochloride, so I saved money two ways.
Obviously, impurities anywhere along the line can bolix up the calculations. The impurities are not likely to affect the performance of the developer if the traditional titration is done at the end. You will wind up with a solution of sodium or potassium paraminophenolate and a sulfite in water with some precipitate which should be kept with the stock. You may not know the exact concentration of the stock if part of the p-aminophenol was the base and part was the hydrochloride, but calculating the concentration from the nominal weight of p-aminophenol and the final volume will be close enough for government work.
What bothers me most is the difference in pH between yours and mine. That could, of course, be due to differences in calibration between meters, were it not for the test strips.
I'm not sure whether to admire or pity you Rodinal-junkies....jeesh, mixing a developer ought to be Betty Crocker, not Los Alamos. I think separating uranium must be easier than mixing this stuff.
I was worried about impurities. So I checked the KOH/NaOH bottles. The KOH says > 87% (kinda low!) but the NaOH says >99.7% and both are behaving somewhat similarly.
I prefer the formula you posted both for reasons of simplicity and economy but I need to sort the pH thing out. I'll see if I can calculate expected pH theoretically. Something that just crossed my mind is that I should also stick the pH meter into a couple of bottles of commercial Rodinal that I have.
But more fun will be to actually test the developer on film and compare results. My worry (other than lack of understanding on my part) is that higher pH may lead to higher grain.