Ilford Ilfostop Working Solution Longevity

[logan2z]

I often have a limited time window to develop film so I'm trying to avoid having to mix up new chemistry for every session - it's obviously not very economical to do that either.

I use my developer one-shot but try and re-use my stop bath and fixer as long as possible. I use a snip test to check the efficacy of my fixer before I use it, but I'm not sure how long I can safely use Ilford Ilfostop as a stop bath. The Ilford data sheet says the working solution is good for 7 days in a full, tightly-capped bottle, but I've heard others on this forum say they use it until the indicator turns purple. Is Ilford being too conservative here? Does anyone here use the working solution for more than 7 days before dumping it?

 

[MattKing]

Working strength, citric acid based Ilfostop is a perfect environment for mould growth - that is the reason that the longevity is limited.
The acetic acid based Kodak Indicator Stop Bath isn't so encouraging to mould, so is a better choice for this approach. Even then, I only keep and re-use mine for a couple of days at most. More typically I use mine one-shot, diluted to half strength.
If your usage is light, diluted white vinegar used one shot is probably a better choice.

 

[Andrew O'Neill]

Do what Matt suggests. I keep a large jug of vinegar in my sink. I got tired of Ilfostop going moldy, even sitting in an airtight bottle. We use Ilfostop at the school I teach at but it makes more sense there as it is used daily. Having that indicator dye is very helpful.

 

[Steve Goldstein]

I've had mold grow in acetic acid stop stored for a long time (six or so months). PE suggested adding 1 gram/liter of Benzoic acid to discourage the little beasties. But really, stop is the cheapest thing you use (after water) so there's little reason to keep it.

You can mix up citric acid stop each session if you don't like the smell of vinegar. Citric acid is inexpensive and widely available in markets, health-food stores, and online. 20 grams per liter, dump at end of session. It's easily soluble in room-temperature water so no waiting. And the dry powder will last forever.

There's no indicator and the capacity is less than an acetic acid stop - I seem to recall reading 15 8x10s per liter. I believe that to be a conservative number, and it probably varies depending on how well you drain your prints before they go into the stop. But it's cheap enough that you can dump the tray in the middle of a long darkroom session and just mix a fresh batch.

FWIW, I use some cheap eBay tally counters to track how many prints go through each tray. The numbers aren't always the same (like forgetting to close down enlarging lens --> skip stop/fix, exposing paper to white light --> skip dev/stop).

 

[grat]

I got about a month of use out of a closed, mostly full bottle of working-strength ilfostop.

Mold was not an issue-- partly, I suspect, because citric acid is deadly to mold. In fact, citric acid is commonly used as a preservative, an anti-bacterial, and an anti-fungal, so I'm not sure where the idea that it's an "ideal" environment for mold. Perhaps the indicator is made from sugar.

It did reach a point where the effect was more "dilution" than "stop", but that was after about 6 weeks of irregular usage.

As others have said, easy enough to mix up your own, and cheap.

 

[MattKing]

I suspect, because citric acid is deadly to mold.

Interesting, as black mould is used to make the non-organic citric acid that is most likely found in the stop bath.

 

[Steven Lee]

@logan2z I use Ilfostop and Kodak's stop interchangeably. Usually I mix 1L in distilled water and use it for 10 rolls spread over 3 months, keeping in a tightly capped bottle. Never had any mold issues and I live in the same climate as you.

This is convenient because my stop bath and fixer prep are synchronized. I re-mix both together after 10 rolls.

 

[DREW WILEY]

Egad. How long do you want your negatives and prints to last? Fixer approaching exhaustion isn't going to be as effective.

 

[logan2z]

Egad. How long do you want your negatives and prints to last? Fixer approaching exhaustion isn't going to be as effective.

I'm not trying to stretch the stop bath beyond its usefulness, just curious if storing it for more than 7 days will still leave it in a usable state. But to be safe, I'll follow Ilford's directions and dump it within a week.

Thanks everyone for the feedback.

 

[brian steinberger]

@logan2z I use Ilfostop and Kodak's stop interchangeably. Usually I mix 1L in distilled water and use it for 10 rolls spread over 3 months, keeping in a tightly capped bottle. Never had any mold issues and I live in the same climate as you.

This is convenient because my stop bath and fixer prep are synchronized. I re-mix both together after 10 rolls.

I do the exact same thing, except I mix up 2 liters and use it for 20 rolls of film. Sometimes up to 3 months as well. Never had a problem either.

 

[Maris]

I use Fotospeed SB50 citric acid stop bath (same formula as Ilford) and diluted 1+19 from the concentrate means a litre of working solution costs me 50 cents. That's so cheap compared to the $40 worth of photographic paper I'll put through it that it's not worth saving. But I do save it because if it stays on the acid side of neutral it will keep working until the indicator dye tells me it has died.

First step in maximising stop bath life is to minimise alkaline developer carry over. I drain freshly developed prints for a number of seconds equal to the diagonal size of the paper measured in inches before transferring them to the stop tray; tedious but seems to work.
At the end of a printing session I transfer used but active stop bath to a big plastic bottle which goes into the darkroom refrigerator. The low temperature, about 4C, inhibits mould growth seemingly indefinitely.

 

[DREW WILEY]

I use fixer one-shot, and mix up just enough for the daily session - that takes, what? - only about 2 minutes. But it saves a lot of time and fuss afterwards. And my preference is TF4 "Archival fixer". Yeah, it costs more; but what is your time and water bill worth? No second bath needed, no HCA, none of the issues described in preceding posts.

 

[grat]

Interesting, as black mould is used to make the non-organic citric acid that is most likely found in the stop bath.

Yeah, I saw that. So I'm admittedly confused, and obviously, anecdotally, people have seen mold form in Ilfostop working solution.