Shelf life of Mytol?

retina_restoration · Mar 28, 2025

I'm having difficulty finding definitive information about the practical shelf life of Mytol, the home-brew version of Xtol. I've seen data that suggests it can't be stored (in a full, tightly capped brown glass bottle) for more than a week, and other data stating it is good for six months. That's a big spread, so I've leaned towards keeping it for no more than a week or ten days.

Can anyone tell me with any certainty what the shelf life of Mytol is, and can you provide references? Thanks.

chuckroast · Mar 28, 2025

I've never used it, but I looked up the formula, and - assuming you have a glass container, mostly full - it sure seems like this should be good for months.

An easy way to test would be to mix up a batch and test develop with it every month until you see failure.

I have routinely used DK-50, D-23, Pyrocat-HD, and D-76 that is at least 6 months old.

retina_restoration · Mar 28, 2025

chuckroast said:
I've never used it, but I looked up the formula, and - assuming you have a glass container, mostly full - it sure seems like this should be good for months.

An easy way to test would be to mix up a batch and test develop with it every month until you see failure.

I have routinely used DK-50, D-23, Pyrocat-HD, and D-76 that is at least 6 months old.

I ask because this is not a pre-manufactured, packaged product; it lacks the sequestering agent(s) that Kodak Xtol contains, and so it behaves differently, hence my specific question. I am well acquainted with the shelf life of products like D-76. But thanks.

chuckroast · Mar 28, 2025

retina_restoration said:
I ask because this is not a pre-manufactured, packaged product; it lacks the sequestering agent(s) that Kodak Xtol contains, and so it behaves differently, hence my specific question. I am well acquainted with the shelf life of products like D-76. But thanks.

I would think the fairly large presence of Sodium Sulphite in the mix would tend to keep it for quite a while. Again, the only way to know this is to test, I guess.

retina_restoration said:
Speaking of D-76 - you are aware of the fact that D-76 increases in activity as it ages, yes? By the 6 month point, stock D-76 is going to be noticeably more active than it was when fresh, resulting in denser, more contrasty negatives.

My understanding is that this is sort of true but somewhat overstated. The increase in pH (increasing alkalinity) is caused by the oxidation of the hydroquinone. This shows up as an issue if you store it in partially full bottles or plastic bottles that are air permeable. Stored properly, D-76 can be used normally for 6 months or more.

See:
https://webionaire.com/2015/08/20/d-76-ph-change/

koraks · Mar 28, 2025

I'm sorry, but I really don't know. I always mix it fresh, use immediately and discard. Given that it's a DIY ascorbate developer, I trust it about as far as I can throw it. It works marvelously, of course - but I wouldn't push the envelope, personally.

retina_restoration · Mar 28, 2025

koraks said:
I'm sorry, but I really don't know. I always mix it fresh, use immediately and discard.

That's been my approach as well, occasionally keeping a full bottle of stock for maybe up to 5 days but no more.

koraks said:
Given that it's a DIY ascorbate developer, I trust it about as far as I can throw it.

Exactly. Ascorbate developers of the DIY kind are not known for having good keeping properties, which is why I ask. Not even Anschel and Troop say anything about this in the book (unless I somehow missed it), which surprises me.

koraks said:
It works marvelously, of course - but I wouldn't push the envelope, personally.

Thanks. I think we have the same approach to it.

Milpool · Mar 28, 2025

retina_restoration said:
I'm having difficulty finding definitive information about the practical shelf life of Mytol, the home-brew version of Xtol. I've seen data that suggests it can't be stored (in a full, tightly capped brown glass bottle) for more than a week, and other data stating it is good for six months. That's a big spread, so I've leaned towards keeping it for no more than a week or ten days.

Can anyone tell me with any certainty what the shelf life of Mytol is, and can you provide references? Thanks.

Without the inclusion of a good iron/copper chelating agent such as DTPA unfortunately you can’t really know in advance how long a home-mixed ascorbate developer will keep.

The good news is you can buy DTPA from Artcraft. It used to be more difficult to source this compound.

There will still be some uncertainty because the rest of the ingredients (in particular sodium sulfite) typically used at home are technical grade, but you’ll still be better off than without the chelating agent.

retina_restoration · Mar 28, 2025

Milpool said:
Without the inclusion of a good iron/copper chelating agent such as DTPA unfortunately you can’t really know in advance how long a home-mixed ascorbate developer will keep.

The good news is you can buy DTPA from Artcraft. It used to be more difficult to source this compound.

There will still be some uncertainty because the rest of the ingredients (in particular sodium sulfite) typically used at home are technical grade, but you’ll still be better off than without the chelating agent.

Thanks for that info.
It appears that you can add 1 gram of DTPA per liter of Mytol to achieve the preservation (and avoid the Fenton reaction ) of the developer, is that about right?
And FWIW, I use the Sodium sulfite from ArtCraft, which is likely standard technical grade, yes?

Milpool · Mar 28, 2025

retina_restoration said:
Thanks for that info.
It appears that you can add 1 gram of DTPA per liter of Mytol to achieve the preservation (and avoid the Fenton reaction ) of the developer, is that about right?
And FWIW, I use the Sodium sulfite from ArtCraft, which is likely standard technical grade, yes?

1-2g/l would be a reasonable starting point. Note that is for the dry salt DTPA Na5 (1g for Mytol likely comes from the XTOL patent in which the example (1) formula contained 1g of DTPA Na5) but what you purchase will be a ~40% solution in water, so you'll need to roughly double it.

The original range in the patent was up to 0.02mol/l of the dry compound which would be a max of 10g/l DTPA Na5, but the example formula calls for 1g.

You could confirm with Mike at Artcraft but I think it's a safe assumption the more standard compounds he supplies are mostly technical grade (same as you get anywhere else dealing to hobbyists). Note I'm not trying to say that's a bad. Technical grade is perfectly fine for photographic purposes. Certain things are just more finicky about how much junk is in the mix - ascorbate is a good example.

All that being said, I still suggest testing any home-mixed ascorbate film developer before use if it is being stored rather than mixed 1-shot.

chuckroast · Mar 28, 2025

Re; D-76 increasing alkalinity. I raised this on the pure-silver list today and this was the response by Dick Knoppow:

Note that this effect, rise in pH, was investigated by Kodak Labs and a paper published about 1928. I am going by memory but can find the citation. The paper shows the rise with time of unused D-76 and the effect on contrast. The paper also shows several variations of M-Q developers. It also shows a buffered version of D-76 which does not display the effect.

D-76 was originally devised as a fine grain developer for a duplicating film for motion picture negatives. It was quickly adopted as the standard developer for negatives. The change in pH and hence activity, was discovered very soon. The buffered version uses equal amounts of borax and boric acid. The formula is:

Kodak D-76d Buffered Borax Developer
Water (at 125F)......................750.0 mL
Metol..................................2.0 grams
Sodium sulfite (anhydrous)...........100.0 grams
Hydroquinone...........................5.0 grams
Borax (granular).......................8.0 grams
Boric acid.............................8.0 grams
Water to make..........................1.0 Liter
The fresh mixed developer will produce a very slight fog. To eliminate this add to the above:
Posassium bromide.....................0.25 grams

Developer which has been used does not need the added bromide.

One source for this formula is:

<https://125px.com/docs/techpubs/kodak/Kodak_formulary.pdf>

I have the original paper somewhere and will try to find it. I am pretty sure it was printed in the Journal of the Society of Motion Picture Engineers as well as other places.

chuckroast · Mar 28, 2025

retina_restoration said:
Exactly. Ascorbate developers of the DIY kind are not known for having good keeping properties, which is why I ask. Not even Anschel and Troop say anything about this in the book (unless I somehow missed it), which surprises me.

I wonder it this is universally true for all ascorbate developers, though. I switched from Pyrocat-HD to Pyrocat-HDC exactly because - even in glycol - I saw a sudden failure of HD. My HDC (again, in glycol) has been going strong for 6+ months at this point in a half full glass bottle.

Milpool · Mar 28, 2025

chuckroast said:
I wonder it this is universally true for all ascorbate developers, though. I switched from Pyrocat-HD to Pyrocat-HDC exactly because - even in glycol - I saw a sudden failure of HD. My HDC (again, in glycol) has been going strong for 6+ months at this point in a half full glass bottle.

The relatively small amount of ascorbate in pyrocat HDC is mostly playing the role of anti-oxidant. It’s still basically a Phenidone-catechol developer. You might not even know if the ascorbate had partially or totally oxidized.

The mytol-type developer is a very different story as the ascorbate is the superadditive developing partner to the Phenidone/Dimezone. And of course an aqueous mix will be more susceptible to premature oxidation (all other things being equal).

chuckroast · Mar 28, 2025

Milpool said:
The relatively small amount of ascorbate in pyrocat HDC is mostly playing the role of anti-oxidant. It’s still basically a Phenidone-catechol developer. You might not even know if the ascorbate had partially or totally oxidized.

The mytol-type developer is a very different story as the ascorbate is the superadditive developing partner to the Phenidone/Dimezone. And of course an aqueous mix will be more susceptible to premature oxidation (all other things being equal).

Ah, OK that makes sense. Thanks for the explanation.

Would mixing Mytol in glycol improve its shelf life or is the cost just not worth it?

Milpool · Mar 28, 2025

chuckroast said:
Ah, OK that makes sense. Thanks for the explanation.

Would mixing Mytol in glycol improve its shelf life or is the cost just not worth it?

You won’t be able to do that - basically because you won’t be able to dissolve the sulfite.

If you want to make a non aqueous, XTOL-like developer realistically your best bet would be a two part formulation - everything but the sulfite in the organic solvent, and then you either make a separate sulfite concentrate or just make the sulfite part one-shot as you go.

A guy named Mark Overton did this work for you. If you are interested look up “Mocon”, which was an XTOL-like two-part formula of the type described above. It was a project with lots of input from some reputable sources, trial and error and testing/objective evaluation.

bluechromis · Mar 28, 2025

Milpool said:
You won’t be able to do that - basically because you won’t be able to dissolve the sulfite.

If you want to make a non aqueous, XTOL-like developer realistically your best bet would be a two part formulation - everything but the sulfite in the organic solvent, and then you either make a separate sulfite concentrate or just make the sulfite part one-shot as you go.

A guy named Mark Overton did this work for you. If you are interested look up “Mocon”, which was an XTOL-like two-part formula of the type described above. It was a project with lots of input from some reputable sources, trial and error and testing/objective evaluation.

Jordan also created an non-aqueous version of Instant Mytol. I have had it last at least six months. https://www.photrio.com/forum/threads/shelf-life-of-mytol.212841/

gkardmw · Mar 28, 2025

There is a version of Instant Mytol that uses TEA and propylene glycol and keeps and works rather well, IMHO. It does, as Milpool suggests, separate the sodium sulfite from the other ingredients, so has 2 baths. Mine still working well after 2 years. PC-512 is a similar developer as developed by relistan and works very well also. The Fenton reaction exists but don't let it detour you from trying PC formulas.

Oh, I see bluechromis beat me to the punch while I was typing.

relistan · Mar 31, 2025

As was said on the thread, aqueous solutions of ascorbic acid/ascorbate developers without copper/iron chelating agents could last a day or a year. It entirely depends on the presence of iron or copper and how much. Both are impurities to be found in other components, so using distilled water is not enough. The alternative to a DTPA is TEA and salicylic acid combo like Ryuji Suzuki used.

But in either case, you'd need to experiment and adjust other components to match the pH. DTPA is an acid and will lower pH, but I am not sure by how much.

All of this is why it's popular to use a glycol solution like Gainer did (and like my PC-512 Borax).

Milpool · Mar 31, 2025

DTPA is supplied as the pentasodium salt (actually alkaline in water). In any case the amounts used are small and should have a negligible effect on target pH in the case of mytol.

The main issue with formulating a single glycol concentrate without water which clones XTOL/mytol is it would lack sulfite - which in the case of solvent developers is playing a significant role in image structure (along with a smaller role in emulsion speed). Without the ~90g/l sulfite XTOL is a different developer.

Edit: If one wants XTOL characteristics in a home-mixed developer without the hassle of ascorbate (ie a relatively known shelf life) my honest suggestion would be to simply go with D-76. The differences are very slight, probably unnoticeable under most circumstances.

relistan · Apr 2, 2025

Milpool said:
The main issue with formulating a single glycol concentrate without water which clones XTOL/mytol is it would lack sulfite - which in the case of solvent developers is playing a significant role in image structure (along with a smaller role in emulsion speed). Without the ~90g/l sulfite XTOL is a different developer.

It does have an effect, but not as much as you might think. The correct ratio of developing agents and the right pH have more effect than the sulfite. The results are different than XTOL but have a very similar look and feel. They are slightly grainier. They are slightly sharper. You can easily reach box speed or slightly higher depending on the film. So it depends on the reasons you use XTOL whether or not it’s a replacement. If longevity is a consideration then it’s better than occasionally used XTOL.

BHuij · Apr 2, 2025

I store mine as a dry powder (with the exception of the phenidone which is mixed as a weak solution in propylene glycol), and mix up immediately prior to use, then use one-shot. In that storage schema, the shelf life is... something I don't concern myself with. "Long enough."

I have often wondered about the viability of mixing it all up in propylene glycol for long-term storage with easier mixing prior to use. Possibly as a single bottle (a la HC-110), possibly as a two-part situation (a la Pyrocat HD). Haven't explored that idea yet though.

Before I got my hands on some PG to dissolve the phenidone, I tried it in 99% isopropyl alcohol. The phenidone managed to go bad within a week (it's possible my alcohol was old and less concentrated than the label would suggest). This resulted in completely dead developer and blank negs. Ever since then I have been religious about doing a clip test while I mix up the developer from powder and get it up to the right temperature. if that film leader isn't dark after a few minutes, I won't commit a roll to it.

Mixed in water, I wouldn't trust it for very long at all. Chemicals are cheap. Latent images on my film are not

chuckroast · Apr 2, 2025

Milpool said:
DTPA is supplied as the pentasodium salt (actually alkaline in water). In any case the amounts used are small and should have a negligible effect on target pH in the case of mytol.

The main issue with formulating a single glycol concentrate without water which clones XTOL/mytol is it would lack sulfite - which in the case of solvent developers is playing a significant role in image structure (along with a smaller role in emulsion speed). Without the ~90g/l sulfite XTOL is a different developer.

Edit: If one wants XTOL characteristics in a home-mixed developer without the hassle of ascorbate (ie a relatively known shelf life) my honest suggestion would be to simply go with D-76. The differences are very slight, probably unnoticeable under most circumstances.

Funny you should say that. I started with film development in Dektol in Tri-Chem packs back in the time of dinosaurs. I quickly moved to Microdol-X and D-76 thereafter and stayed there for decades until I switched to HC-110. In the past 10 years I've done a lot with D-23, DK-50, PMK, and Pyrocat-HD(C).

While each of these has their virtues, I am always amazed when I return to D-76 as to just how good and flexible this stuff is. I just did a 45min EMA development of Fomapan 200 in D-76 1+3 over the weekend and got absolutely terrific negs.

I think it is likely true that the differences between developers are less significant that we'd like to believe. What's more important is knowing how to use them properly.

Shelf life of Mytol?

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