What's wrong with my Foma RC paper?

tezzasmall · Jul 3, 2025

Well done dcy on finally sorting the issue out. In the distant past I had a similar problem and like you I finally sorted the problem out by making some fresh D72. The original stock developer looked good, so I didn't consider this to be the problem initially. So, sometimes the answer is right there, waiting for that Dohhh! moment to happen.

As for E23, I have used it and it was easy as any to mix up, but I generally ignore formulas which say, 'Add 1/2 of the final liquid amount and mix the chemicals in'. I now use 2/3 to 3/4 of the warm / hot water listed, and have found all chemicals mix in fine then. The mixture is then finally topped up to the recommended amount.

The only thing with home-mixed E23, as you will quickly find out, is it's short shelf life. The same with film developer E76. After much reading, I am trying out a chelating agent, of which I presume the Adox Eco developer uses, to extend the developers lifespan.

As for named paper developers, I used Ilford MG for many years, before starting to mixing my own, and found it to be great, both in use and its storage life. In fact, I recently found a single one litre bottle of the concentrate tucked away at the back of a darkroom shelf. It had been decanted from a five litre bottle, which is how I buy / bought my fixers and developers, as you basically get two litres free, when the prices are compared between one and five litre containers. It must be about five plus years old and it still works like it was freshly bought! But I'll carry on mixing my own various developers and toners, for like you, I enjoy it as part of my photography.

Terry S

dcy · Jul 3, 2025

Don_ih said:
I actually meant are you sure that what you think is ascorbic acid is actually ascorbic acid?

Ah. That makes a lot more sense.

Yes. I did consider that also and that is in fact a very strong possibility. This is in fact the #1 thing I wanted to improve about my process before I even begun. I'll explain: The product I used is actually a set of Vitamin C tablets that I got from the grocery store a year ago when I decided to make PC-TEA. That means that, while they are mostly ascorbic acid, they also have other ingredients such as a binding agent to keep the tablet together. I still used them because they're still mostly ascorbic acid and my PC-TEA worked well. So my plan was to finish off most of the bottle and then order a bag of pure ascorbic acid. The E-72 that I just made was enough for that, and I did order a bag. Anyway, it is possible that either some of the binding agents or an imperfection in how I ground the tablets down made it harder to dissolve.

koraks · Jul 3, 2025

dcy said:
Anyway, it is possible that either some of the binding agents or an imperfection in how I ground the tablets down made it harder to dissolve.

The fillers are typically stuff like calcium carbonate - which virtually doesn't dissolve. So yeah, the stuff floating around was mostly just basically inert material anyway.

Don_ih · Jul 3, 2025

That solves the mystery. And the stuff works, so that's good.

Bill Burk · Jul 4, 2025

I think it’s cool you found different papers react differently to the D-23 you mixed.

If you’d used regular premixed developer you’d never have run into that.

Maybe you can find the root cause, which will make you better at mixing your own. Maybe the pH was too low and you could’ve just adjusted something. Maybe it was the water.

dcy · Jul 4, 2025

Bill Burk said:
I think it’s cool you found different papers react differently to the D-23 you mixed.

If you’d used regular premixed developer you’d never have run into that.

No no no. The original problem was with a premixed developer. I was using the Arista paper developer. Problem was probably that a half-empty bottle of concentrate has a shelf life shorter than a year.

Bill Burk said:
Maybe it was the water.

FWIW, I use distilled water for everything except the final rinse.

koraks · Jul 4, 2025

dcy said:
FWIW, I use distilled water for everything except the final rinse.

If it's any consolation, the water is virtually never the problem, anyway. Commercial chemistry is formulated in such a way as to be tolerant of a wide range of water quality, which means that plain tap water will generally work in most parts of the world except perhaps in very extreme cases with e.g. exceptionally high iron content. With DIY chemistry you can notice cloudiness in e.g. developers if you don't use a sequestering agent. This is generally harmless.

Bill Burk · Jul 4, 2025

dcy said:
No no no. The original problem was with a premixed developer. I was using the Arista paper developer. Problem was probably that a half-empty bottle of concentrate has a shelf life shorter than a year.

FWIW, I use distilled water for everything except the final rinse.

Ok, maybe mixing your own would have been better.

I use bottled water to make the stock, but tap water to mix working solution and stop bath and fix (from concentrate). All the water goes through a single stage filter but I just use the bottled water sparingly. But then the final rinse with Photo-Flo (for film) I use bottled water again because I don’t want water spots.

koraks · Jul 4, 2025

To clarify, by "bottled water" I assume you mean distilled or demineralized water, correct? The term 'bottled water' can also refer to water sold for human consumption, sometimes called 'mineral water'. This is often relatively rich in dissolved salts, depending on origin.

dcy · Jul 4, 2025

Bill Burk said:
Ok, maybe mixing your own would have been better.

I could also have transferred the contents to a smaller glass bottle. I did not think of this at the time.

Bill Burk said:
But then the final rinse with Photo-Flo (for film) I use bottled water again because I don’t want water spots.

For film I use tap water for the Ilford wash, and then one last rinse with distilled water and Photo-Flo. That's probably excessive, as either just Photo-Flo or distilled water should be enough on its own, but distilled water is cheap and I happier knowing I won't get water spots.

MTGseattle · Jul 4, 2025

I just want to chime in and compliment @dcy on pushing through a few different problems. It's good to see someone on the journey having setbacks and successes. I can't seem to be bothered to even mix up any chemistry lately. I've built myself into a bunker worth of old/expired/formerly highly regarded papers, and the thought of running it all through various tests to check viability does not excite me. I do have some film to process, so maybe that will shake me out of my quasi-slump.

I'm sure it's been said before, but if you run into weird results and you suspect your chemistry do not change chemistry, just mix some fresh stuff up and repeat your process.

Don_ih · Jul 4, 2025

MTGseattle said:
slump

Happens to everyone. Sometimes, you need to shift your attention elsewhere for a while.

As for your paper, make sure you have some benzotriazole and potassium bromide - and maybe a set of A-B lith dev....

Bill Burk · Jul 4, 2025

dcy said:
For film I use tap water for the Ilford wash, and then one last rinse with distilled water and Photo-Flo. That's probably excessive, as either just Photo-Flo or distilled water should be enough on its own, but distilled water is cheap and I happier knowing I won't get water spots.

Ah you’re calling “rinse” what I call “wash” and you’re doing same as me, the last contact with water is Photo Flo and bottled water. Note: I remove the film from the reel and then see-saw it through the Photo-Flo. My reels came out of plain water so they don’t need any further attention- just put them up to dry. If you dip film with the reels then you have to wash the reels. And I would worry about bubbles.

I will use the cheapest water, tending to get the Crystal Springs purified drinking water (so I could drink it if there’s an earthquake, or bring it on a day trip for drinking water in the car).

koraks · Jul 5, 2025

Bill Burk said:
I will use the cheapest water, tending to get the Crystal Springs purified drinking water

Have you looked at the mineral content of that water and compared it to your tap water? Around here, the water companies publish (for reasons of legal compliance) the composition of the water they deliver to homes, and the mineral content of drinking water is listed on the bottle, in which case it's easy to compare. I'm asking because bottled spring water can be high in e.g. calcium content, making it not a very suitable candidate for a final rinse - at least not anymore suitable than tap water. But it depends on specific characteristics.

If someone wants to avoid water spots/drying marks due to mineral content in the water, I'd suggest using demineralized water, which is available in virtually all supermarkets.

dcy · Jul 5, 2025

koraks said:
Have you looked at the mineral content of that water and compared it to your tap water? Around here, the water companies publish (for reasons of legal compliance) the composition of the water they deliver to homes, and the mineral content of drinking water is listed on the bottle, in which case it's easy to compare. I'm asking because bottled spring water can be high in e.g. calcium content, making it not a very suitable candidate for a final rinse - at least not anymore suitable than tap water. But it depends on specific characteristics.

I found this paper from 2020 with relevant information in Table 3. For someone in North America, spring water is "probably" slightly better than tap water, and mineral water is probably significantly worse, all with error bars so large as to make the comparison essentially a coin toss.

For Europe, the table doesn't include much information about tap water, but the error bars for bottled water are just as large.

Code:

Water source                            Calcium (mg/L) (mean ± stdev)
---------------------------------------------------------------------
North American tap water   
     Surface water sources (n = 36)            34 ± 21
     Ground water sources (n = 8)              52 ± 24
     U.S. tap water (n = 33)                   51 ± 29
     Canada tap water (n = 6)                  49 ± 53
North American bottled waters   
     Spring water (n = 28)                     18 ± 22
     Mineral water (n = 9)                    100 ± 125
European bottled waters   
     Low mineralization water (n = 40)         60 ± 40
     Moderate mineralization water (n = 26)   262 ± 139
     High mineralization water (n = 7)         60 ± 59

koraks · Jul 5, 2025

dcy said:
For Europe, the table doesn't include much information about tap water

Tap water is insanely variable w.r.t. mineral content. The numbers would be all over the place.
For instance, tap water in my home would have a calcium content of 40-60mg/l depending on which source we're being fed from. Drinking water companies in my country are legally obliged to keep the calcium content between ca. 40 and 100mg/l (5.6-14DH).

According to the table you found, American 'spring' water should indeed be quite low in calcium, so it looks a bit better than tap water, but evidently much worse than demineralized. At least for this purpose.

What's wrong with my Foma RC paper?

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