Parodinal, to filter or not to filter?

jorgemtrevino · Jul 9, 2022

Hi folks, I'm in Mexico and guess that if I might get commercial Rodinal (Adonal, R09 or whatever it's called nowadays) I wouldn't be trying to brew my own. Apologies if this has been asked and answered a hundred times but I've read dozens of threads and cannot get a simple straight answer.

I had a successful batch following the "standard" Rx of 15g acetaminophen (extracted from 20 grinded tablets of generic paracetamol, grinded in an old cofee mill diluted in 100ml H2O and strained through a stainless steel mesh cofee filter. To this I added the Solution B of 20g pure sodium hydroxide (diluted in 100ml 10ºC water) to which I added the 50g sodium sulphite anhidrous then slowly added to the acetaminophen solution. Let stand for 4 days and processed a 120 roll of HP5+ in 1:50 for 7 minutes. Got slightly flat negatives but very fine grain.

The question: Lotsa people say the precipitate and cloudiness of the stock is essential and we should agitate the stock before preparing the working dilution. Others say the precipitate is just paracetamol filler and should be discarded. What gives? Totally confused.

Another question; got some fog (not too much). Should I add some potassium bromide?

Thanks for your comments.

koraks · Jul 10, 2022

I've always understood that the solid sulfite muck at the bottom essentially ensures that an excess of sulfite is always present to protect the developer from oxidation. Then again, I can imagine that the excess is also sufficient if you filter out the undissolved solids and perhaps try and protect the concentrate a bit from oxygen in other ways.

Btw, I don't think the precipitate is either sulfite or tablet fillers -it's probably both, at least based on my brief experience making parodinal. Most of it at least in my case was sulfite. The tablet fillers are usually more flaky/fluffy whereas the sulfite tends to create a paste-like muddy layer.

I never filtered mine and just accepted it like it was (and moved on to other developers soon after).

jorgemtrevino said:
Should I add some potassium bromide?

Hey, it's your universe, experiment
Depending on the origin of the fog, it may or may not help.

Gregorius63 · Jul 10, 2022

jorgemtrevino said:
Hi folks, I'm in Mexico and guess that if I might get commercial Rodinal (Adonal, R09 or whatever it's called nowadays) I wouldn't be trying to brew my own. Apologies if this has been asked and answered a hundred times but I've read dozens of threads and cannot get a simple straight answer.

I had a successful batch following the "standard" Rx of 15g acetaminophen (extracted from 20 grinded tablets of generic paracetamol, grinded in an old cofee mill diluted in 100ml H2O and strained through a stainless steel mesh cofee filter. To this I added the Solution B of 20g pure sodium hydroxide (diluted in 100ml 10ºC water) to which I added the 50g sodium sulphite anhidrous then slowly added to the acetaminophen solution. Let stand for 4 days and processed a 120 roll of HP5+ in 1:50 for 7 minutes. Got slightly flat negatives but very fine grain.

The question: Lotsa people say the precipitate and cloudiness of the stock is essential and we should agitate the stock before preparing the working dilution. Others say the precipitate is just paracetamol filler and should be discarded. What gives? Totally confused.

Another question; got some fog (not too much). Should I add some potassium bromide?

Thanks for your comments.

I have always used 30 tablets for my recipe, (30 x 500mg=15 grams). I also grind the tablets and extract the acetaminophen with alcohol (denatured), pour off alcohol / acetaminophen mixture from tablet fillers and let alcohol evaporate. It turns into pink crystals that are weighed and added to formula.
This results in less sediment for your home made Rodinal, I have some two years old that works great and has a few crystals in the bottom, but no sludge.

jorgemtrevino · Jul 11, 2022

koraks said:
I've always understood that the solid sulfite muck at the bottom essentially ensures that an excess of sulfite is always present to protect the developer from oxidation. Then again, I can imagine that the excess is also sufficient if you filter out the undissolved solids and perhaps try and protect the concentrate a bit from oxygen in other ways.

Btw, I don't think the precipitate is either sulfite or tablet fillers -it's probably both, at least based on my brief experience making parodinal. Most of it at least in my case was sulfite. The tablet fillers are usually more flaky/fluffy whereas the sulfite tends to create a paste-like muddy layer.

I never filtered mine and just accepted it like it was (and moved on to other developers soon after).

Hey, it's your universe, experiment
Depending on the origin of the fog, it may or may not help.

The jury's out: no filtering! Thanks for the reply, now to refine times. I loved Rodinal when it was freely available.

jorgemtrevino · Jul 11, 2022

Gregorius63 said:
I have always used 30 tablets for my recipe, (30 x 500mg=15 grams). I also grind the tablets and extract the acetaminophen with alcohol (denatured), pour off alcohol / acetaminophen mixture from tablet fillers and let alcohol evaporate. It turns into pink crystals that are weighed and added to formula.
This results in less sediment for your home made Rodinal, I have some two years old that works great and has a few crystals in the bottom, but no sludge.

I tried dissolving with 99° isopropyl and didn't work. Will make another attempt with non-denaturated 96° cane alcohol. For important rolls I'll keep using HC-110 @ 1+63 Dil B1/2.

Gregorius63 · Jul 11, 2022

jorgemtrevino said:
I tried dissolving with 99° isopropyl and didn't work. Will make another attempt with non-denaturated 96° cane alcohol. For important rolls I'll keep using HC-110 @ 1+63 Dil B1/2.

The acetaminophen is dissolved in the alcohol, what is left is the tablet fillers. Carefully pour off the liquid and leave the filler in your glass or jar you are using. The liquid alcohol is poured in another glass container or bowl to allow alcohol to evaporate. What is left is pinkish crystals that are acetaminophen.

Gregorius63 · Jul 11, 2022

Fomapan 100 dev in parodinal 1+50 8 minutes
Rolleiflex Automat 75mm f3.5 xenar

Donald Qualls · Jul 12, 2022

FWIW, I've never filtered Parodinal. I usually use a syringe to take up the concentrate for dilution, but without agitating the concentrate bottle (I've stored it in a wide mouthed Mason type jar in the past).

Might have to get some denatured 95% ethanol to try the dissolve/evaporate extraction method. Seems cheaper than buying pure acetaminophen under its IUPAC name from chemical suppliers (especially since I don't need multiple kilos of the stuff at any one time).

jorgemtrevino · Jul 12, 2022

Gregorius63 said:
The acetaminophen is dissolved in the alcohol, what is left is the tablet fillers. Carefully pour off the liquid and leave the filler in your glass or jar you are using. The liquid alcohol is poured in another glass container or bowl to allow alcohol to evaporate. What is left is pinkish crystals that are acetaminophen.

Obliged! Sorry for the tardy reply; day job.

Right now I´m letting my last batch mature and precipitate (in water) but will decant it.

BTW, for reasons I cannot fathom, my current batch came out "strong" and overdeveloped Tri-X by about one stop (can't be sure as my contrast analyzer went with the rest of my wet printing gear three years ago). I followed the standard recipe for 250ml: 15g paracetamol, 50g sulfite and 20g lye. Developed 13 min as per The Massive Dev Chart with gentle agitation. Loaded a test roll of 12 frames and will cut the time in half; see what happens.

I have another 250ml with some KBr that I used to develop some expired 120 HP5+ that has started to fog: shot at 200 (+1), followed the Digitaltruth instructions for ISO 400 and it came out perfect for scanning or printing at grade III. Very fine grain.

I'll experiment with that, just getting bored with shooting figurines.

Couple more questions about the paracetamol dissolved in alcohol: how much alcohol for the (30 or 20) tablets and how long did it take to completely evaporate?

jorgemtrevino · Jul 12, 2022

Donald Qualls said:
Might have to get some denatured 95% ethanol to try the dissolve/evaporate extraction method. Seems cheaper than buying pure acetaminophen under its IUPAC name from chemical suppliers (especially since I don't need multiple kilos of the stuff at any one time).

Thanks Donald, same here. The nearest generic pharmacy gives me 20x .750 Paracetamol for about $1.50 (USD). Suspension solids are a characteristic, not a problem. I also stored the parodinal in ex-marmalade jars and use a vet syringe to pull it from the top. Once it's mixed 1:50 it´s clearer than the water I get from the tap. (not really, the city cleans it, but in any case we have a processor in the kitchen and filters in the fridge).

Gregorius63 · Jul 13, 2022

jorgemtrevino said:
Obliged! Sorry for the tardy reply; day job.

Right now I´m letting my last batch mature and precipitate (in water) but will decant it.

BTW, for reasons I cannot fathom, my current batch came out "strong" and overdeveloped Tri-X by about one stop (can't be sure as my contrast analyzer went with the rest of my wet printing gear three years ago). I followed the standard recipe for 250ml: 15g paracetamol, 50g sulfite and 20g lye. Developed 13 min as per The Massive Dev Chart with gentle agitation. Loaded a test roll of 12 frames and will cut the time in half; see what happens.

I have another 250ml with some KBr that I used to develop some expired 120 HP5+ that has started to fog: shot at 200 (+1), followed the Digitaltruth instructions for ISO 400 and it came out perfect for scanning or printing at grade III. Very fine grain.

I'll experiment with that, just getting bored with shooting figurines.

Couple more questions about the paracetamol dissolved in alcohol: how much alcohol for the (30 or 20) tablets and how long did it take to completely evaporate?

I used about 150ml of denatured alcohol in a 500ml pickle jar. I let it sit for about 15 minutes and poured the alcohol into a glass pie pan in the garage because of smell. It took 10-12 hours to evaporate. Your time may vary due temp/humidity in your location

jorgemtrevino · Jul 13, 2022

Gregorius63 said:
I used about 150ml of denatured alcohol in a 500ml pickle jar. I let it sit for about 15 minutes and poured the alcohol into a glass pie pan in the garage because of smell. It took 10-12 hours to evaporate. Your time may vary due temp/humidity in your location

Thanks, proportion (1:10) sounds about right. Did the net weight match? My darkroom has a good extractor into the yard. I can leave the pan there (will have to smuggle the glass pan surreptitiously tho, my wife is adamant that photo chems are poisonous!!).

PS, goofed with a film test, diluted 1:25 and developed for 1:50. Got this!

jorgemtrevino · Jul 13, 2022

Gregorius63 said:
Fomapan 100 dev in parodinal 1+50 8 minutes
Rolleiflex Automat 75mm f3.5 xenar

Tonality looks great and so does the grain but then 120 is 4X the area of 35. Rollei TLRs are like Swiss watches of lore, no?

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