Well, mine that I mixed from p-aminophenol and that had the extra 9 grams/liter, did not oxidize rapidly. OTH, the stuff I mixed from the old p-aminophenol.HCl was black as coal from the start. I seem to remember that the kit I got from the Formulary also produced very dark Rodinal from the start.Gerald Koch said:I wonder how many complaints Photographer's Formulary get every year to the effect "I mixed everything in the kit but the Rodinal turned out completely black." It needs to be stressed that the developer will oxidize VERY rapidly if there is ANY excess hydroxide. By leaving a small amount of precipitate you insure that there is no excess. Think of the end point in a titration where the indicator is the precipitate.
gainer said:You were right, Jurgen. I doctored the remains of the 500 ml I had made by adding 10 grams of sodium bisulfite to bring the pH down roughly where it would be without the extra 9 grams/liter of sodium hydroxide. The HP5+ negative at 1+25 is much better. I'll try a new batch from scratch when my supplies come in. Thanks.
The formula which I use says to first add x milliliters of the hydroxide solution. Then it says to add the hydroxide slowly until there is a sudden darkening of the solution. At this point the hydroxide should be added very slowly until most of the remaining precipitate dissolves but a small amount is left. Using this method the bulk of the hydroxide can be added all at once.gainer said:The problem that I had with trying to leave a litle precipitate was that the reaction upon adding hydroxide solution was slow. The visual feedback was delayed enough that I added too much hydroxide.
Criticism is good. I had to do enough of it and endure enough of it while working at NASA to know the value of it.Jurgen said:I don't want to be critical but I did a few calculations on the rodinal formula in the darkroom cookbook. After converting the HCl salt to base and assuming all 400ml of KOH is used it appears to be about 0.5 molar in para aminophenol, about 55 grams. This would require about 20 grams of NaOH. Not sure about the sulfite.
Also the pH of your formula at 1:25 would be about 12, at 1:50 about 11.6.
Jurgen
I wonder what they will charge. I have always found that their kits are overpriced for what you get.Lee Shively said:Not being of the chemical-concocting type, I kind of lost track of this thread with all the formulas involved. Somebody might have mentioned it and I missed it, but Photographer's Formulary website says they will be introducing an already mixed, liquid form of their Rodinal substitute shortly. The mix-it-yourself kits have been discontinued.
gainer said:I have found that the following recipe gives the results of Rodinal with no fuss in the making.
Start with 700 ml water at room temperature.
Add 170 grams of anhydrous sodium sulfite, 14 grams sodium hydroxide, and stir till dissolved. Warming it a little won't hurt. Add 40 grams p-aminophenol (not the hydrochloride). It will not all dissolve. Add water to make 1 liter. When you transfer from the mixing vesel to storage, do not filter out the sediment. Use it like AGFA Rodinal.
jim appleyard said:Am I missing something?
Red Devil brand lye is very good. It is a free flowing granular product, perfectly white, and the consistency of fine sugar. It also keeps better, not taking up moisture readily, as it comes in a screw cap bottle.Photo Engineer said:The Lye that I get here is often rather crummy stuff. If it is not pure white flakes, don't use it.
Finally, the real Rodinol formula is unique and does not need any benzotriazole or bromide as antifoggant. Its particular chemistry related characteristics have not really been caught or captured by anyone here. I wonder if anyone out there (that I have not told) will be able to discover what I'm referring to?
One thing I must point out is that properly mixed Rodinol or its work alikes should not ever have a purple color. The final stock solution should resemble tea.
jdef said:Thank you Ron and Gerald for sharing your expertise, it is most welcome.
jdef said:I have found that it is possible to make a developer that does not require any antifoggant, gives good film speed and fine grain, but is not as active as Rodinal. To match (or excede) the activity of Rodinal, I've had to increase the pH, and add a drop or two of BZT.
jdef said:I'm seeing a range of colors from very brown-purple, to the pale lilac color, with the light tea in between. I've assumed that the dark brown stuff is more oxidized than the lighter stuff, and that the lilac stuff hasn't fully hydrolysed.
Ron, what does the purple color indicate?
Photo Engineer said:One thing I must point out is that properly mixed Rodinol or its work alikes should not ever have a purple color.
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