What could go wrong

iakustov · Jul 2, 2021

Today I mixed a fresh stock of Pyrocat-M (stock A: metol 2.5g/l, metabisulfite 10g/l, pyrocatechin 50g/l) and developed four FP4 4x5 sheets with standard dilution (I use 20% sodium carbonate for stock B so my dilution is 1+5+94). I presoak for a couple of mins.

They came out ugly - very thin, with fingerprints, uneven density / stain across the sheet.

Per my understanding any fingerprints should be gone during development, I never had such problems before that. Last time I prepared such a stock was a year ago and it worked fine, I have not changed anything since then except for the fixer - previously used Rapid Fixer from Ilford, now use rapid neutral fixer hypo + ammonium chloride based (Agfa 304 analog by Rudeofus, he posted the formula some months ago).

I can say I trust my exposure, development techniques as today I developed some sheets of other film in XTOL just before that. I also trust Metol as I mix other metol-based developers with no issues.

I measured pH of developer solution and it is 11. Fixer’s pH is 6.4.

Can pyrocatechin go bad even if stored in tight container? This is how it looks like now:

It seems to smell like it should be, but more of like gouache paints though.

Don_ih · Jul 2, 2021

My unopened bottle, which is a few years old, has almost white catechol in it.

iakustov · Jul 2, 2021

Don Heisz said:
My unopened bottle, which is a few years old, has almost white catechol in it.

Thanks! My metol is also not white, but works fine..

michael_r said:
Did you use an acid stop bath or thorough running water wash before fixing?

Brown catechol indicates a fairly advanced state of oxidation. Fresh catechol should basically be white. As it oxidizes it will start to go grey, then brown, then brown-black when it is dead.

Thank you! I use tap running water for the stop bath.
So, it looks like I have to search for fresh catechol now.

GLS · Jul 2, 2021

iakustov said:
Can pyrocatechin go bad even if stored in tight container? This is how it looks like now:

That doesn't look good at all. As already mentioned, pure catechol is colourless. As it oxidises it will turn yellow, then brown, then darken further with age. Your sample looks in bad shape and should be replaced. Newly purchased material should be white to just off-white, depending on the grade.

To prolong the longevity, you could make up a large batch of part A in glycol (in which oxygen has very low solubility). This is commonly done with Pyrocat-HD so I'm sure would also work with the M variant.

iakustov · Jul 2, 2021

michael_r said:
One quick thing I suggest would be to re-fix the film in fresh Ilford Rapid Fixer and see if anything at all changes. This will not address all of the problems but might give you some more information.

Bad catechol in this formula could potentially cause all sorts of staining issues and loss of emulsion speed.

While you’re at it you might want to get fresh metol, depending on how discoloured/dark it is, as well as new sulfite and metabisulfite/bisulfite if they are very old.

I just developed a sheet of FP4 whole plate in fresh home mixed D76 and it came out just fine, so can rule out the fixer, I suppose. My metabisulfite is fresh, so it looks like catechol is indeed the issue.
If I remember correctly there was a discussion about proper colour of Metol recently and maybe there are some variations non-white which work fine, I dont know. I will search for fresh metol and catechol anyway, it just that these are imported over here, not always in stock / available and quality could differ.

GLS said:
That doesn't look good at all. As already mentioned, pure catechol is colourless. As it oxidises it will turn yellow, then brown, then darken further with age. Your sample looks in bad shape and should be replaced. Newly purchased material should be white to just off-white, depending on the grade.

To prolong the longevity, you could make up a large batch of part A in glycol (in which oxygen has very low solubility). This is commonly done with Pyrocat-HD so I'm sure would also work with the M variant.

Thanks, I am more assured now. I have not tried, but Sandy here suggests that the metol version should be made in water rather than glycol due to solubility concerns.

GLS · Jul 2, 2021

iakustov said:
I have not tried, but Sandy here suggests that the metol version should be made in water rather than glycol due to solubility concerns.

Makes sense if using the salt form, but the metol could be free based as Sandy mentions. It is an extra step though. Even with the salt, you could probably pre-dissolve it in a small amount of water, then add that solution to the main glycol mixture. Anyway, the glycol was just an idea. No doubt water is fine as long as your ingredients are fresh and you use up the part A concentrate before it starts going bad.

mrosenlof · Jul 2, 2021

The fingerprints usually come from fingers in fixer and then touching the film before washing the fix off well enough. At least that's the first thing I think when I see prints like this.

koraks · Jul 2, 2021

GLS said:
That doesn't look good at all.

I disagree. All the pyrocatechol I've had looked exactly the same and has always worked just fine.

cliveh · Jul 2, 2021

Why don't you use a developer from a developer manufacturer, rather than mix your own?

GLS · Jul 2, 2021

mrosenlof said:
The fingerprints usually come from fingers in fixer and then touching the film before washing the fix off well enough. At least that's the first thing I think when I see prints like this.

I was thinking the same thing.

koraks said:
I disagree. All the pyrocatechol I've had looked exactly the same and has always worked just fine.

Maybe, but the point is it is certainly not very pure if it looks like that, and there is no way of knowing the exact extent of oxidation or the degree to which other impurities are present from just the appearance (yours may have been in better shape than his). In lieu of spectroscopic analyses it is a qualitative judgement in other words, and if there is a problem with the developer this catechol is certainly a possible culprit.

Raghu Kuvempunagar · Jul 3, 2021

koraks said:
I disagree. All the pyrocatechol I've had looked exactly the same and has always worked just fine.

Fresh Catechol I get from a reputed manufacturer looks exactly like OP's but always worked fine for me. However, before mixing a Pyrocat concentrate, it's always a good idea to do a simple test - mix 0.1g of Sodium Sulphite followed by 0.5g of Catechol and 5g of Sodium Carbonate in 1l of water. Use this fresh working solution to develop a less important film and verify that it gives expected result.

Pat Erson · Jul 3, 2021

iakustov said:
Thanks! My metol is also not white, but works fine..

Mine is brown/red but it works fine...

esearing · Jul 3, 2021

My 2+ year old cachetol is still white.

Your part B sodium carbonate should be 5G per liter , mixed fresh working solution, but I have had problems with inconsistency doing this. I think the monohydrate absorbs water fairly quickly so probably is not a true 5G/liter and is not quite active enough.
I found that Potassium Carbonate or Part B from a Pyrocat-HD kit (750g/liter Potassium Carbonate stock) works better and is more consistent when used 1:1:100 for 8x10/single roll. I buy it alone from Bostick and Sullivan

In a SP445 tank I generally use 4A : 3.5B : 500W for a single 4x5 sheet of FP4+ (13mins @70* / presoak 5mins, 2mins initial agitation, then agitate 20 seconds every 2-3 mins) , water stop, TF5 fixer.
Pyrocat M gives a slightly flatter negative than HD but holds the highlights nicely.
This is my working method for my print desires, but you may like a more contrasty thicker negative so lean toward the 1:1:100 mix for initial testing.
You can safely knock it down to about 3.5 : 3 : 500 for minimal agitation schemes with double the time.

If you have sweaty hands use a nitrile glove when loading/unloading film to avoid the finger prints.

iakustov · Jul 6, 2021

mrosenlof said:
The fingerprints usually come from fingers in fixer and then touching the film before washing the fix off well enough. At least that's the first thing I think when I see prints like this.

I use SP810 tray and only touch negatives when loading, I unload with gloves on and haven't had such problems with sheet film before so I believe the fingerprints were not removed during development.

GLS said:
Maybe, but the point is it is certainly not very pure if it looks like that, and there is no way of knowing the exact extent of oxidation or the degree to which other impurities are present from just the appearance (yours may have been in better shape than his). In lieu of spectroscopic analyses it is a qualitative judgement in other words, and if there is a problem with the developer this catechol is certainly a possible culprit.

So, it looks like you cannot tell if catechol is fine just by judging its colour..

Raghu Kuvempunagar said:
Fresh Catechol I get from a reputed manufacturer looks exactly like OP's but always worked fine for me. However, before mixing a Pyrocat concentrate, it's always a good idea to do a simple test - mix 0.1g of Sodium Sulphite followed by 0.5g of Catechol and 5g of Sodium Carbonate in 1l of water. Use this fresh working solution to develop a less important film and verify that it gives expected result.

Thanks, I will do that from now.

esearing said:
My 2+ year old cachetol is still white.

Your part B sodium carbonate should be 5G per liter , mixed fresh working solution, but I have had problems with inconsistency doing this. I think the monohydrate absorbs water fairly quickly so probably is not a true 5G/liter and is not quite active enough.
I found that Potassium Carbonate or Part B from a Pyrocat-HD kit (750g/liter Potassium Carbonate stock) works better and is more consistent when used 1:1:100 for 8x10/single roll. I buy it alone from Bostick and Sullivan

In a SP445 tank I generally use 4A : 3.5B : 500W for a single 4x5 sheet of FP4+ (13mins @70* / presoak 5mins, 2mins initial agitation, then agitate 20 seconds every 2-3 mins) , water stop, TF5 fixer.
Pyrocat M gives a slightly flatter negative than HD but holds the highlights nicely.
This is my working method for my print desires, but you may like a more contrasty thicker negative so lean toward the 1:1:100 mix for initial testing.
You can safely knock it down to about 3.5 : 3 : 500 for minimal agitation schemes with double the time.

If you have sweaty hands use a nitrile glove when loading/unloading film to avoid the finger prints.

I use 1+5+94 dilution with 20% sodium carbonate as part B per published formula, so it is 10g of sodium carbonate per litre in a working solution, but I did not have problems with previous batches.
As I said, I never experienced fingerprints on the developed negatives before, so something definitely went wrong during development.

GLS · Jul 6, 2021

iakustov said:
So, it looks like you cannot tell if catechol is fine just by judging its colour..

Not accurately no, but it is a good indication. The closer it is to white the better.

michael_r said:
This assumes one is getting a decent quality (technical grade) compound to begin with

This illustrates the huge variance the subjective terms "fine" or "decent" can encompass. Much of those value judgements depend on intended use or how much uncertainty one is willing to accept in the end result. Personally if I was mixing my own developers I would only want to use the highest purity ingredients I could get my hands on, but then I am a professional chemist so naturally incline that way

GLS · Jul 6, 2021

michael_r said:
By the way, since you are a professional chemist, let us know if you have any "ins" with a supplier like Sigma or something .

Suppliers like Sigma, Fisher, TCI etc unfortunately only sell to registered companies, institutions and so on, and not to individuals (even if you are a qualified chemist). I could probably work out an arrangement at work to order extremely high purity chemicals in order to make developers for my own use, but for example I remember pricing up what it would cost to make Pyrocat-HD from scratch and it was pretty much a wash cost-wise with the commercial stuff. I've no doubt the part A I could make would be higher quality of course, but not enough of a difference to be worth the hassle.

iakustov · Jul 23, 2021

I purchased new catechol, but its colour is similar to one in my post #1. I mixed a new batch from it and developed a not so important sheet, and it came fine.
So, from now on everytime I mix a new batch I will make a test first, as it looks like the catechol I can get in retail over here is not white.

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