Fungus in Stop Bath

[Adrian]

Hi,

I use Ilford Stop Bath diluted 1:19 (the regular version with the yellow indicator). It is stored at a reasonably low temperature, usually < 15 deg. C. I have found in the past that a jelly-like substance can form. I normally remove it with a syringe. Just cleaning out the bottle in which the made-up solution is stored with hot water is not enough. It seems to breed and return. I had to throw away the container (a 1L plastic container) and make up fresh solution in a new container. However, I have noticed it has now returned.

This time I took a sample and looked at it under a phase contrast microscope at 600x See attached photo. I am not a biologist let alone an expert on fungi, maybe there is somebody on this forum who is and can advise as to what it is. To me, it looks like a fungus with spores and branched stems both visible in the image.

Has anyone else had this problem? How did you get rid of it?

[John King]

Yes seen it before. 'orrible stuff. You will be using the non smelly variety of stop bath based on Citric Acid. Some forms of mold/fungus can develop on the surface because bacteria can survive on the surface. As far as I can tell there will be no ill effects to the working of the solution, just filter the mold off using a paper coffee filter in a funnel.

Or-

Go back to using Acetic Acid based stop bath, that will remain growth free. That's what I did. The Kodak variety is also a lot cheaper than the Ilford offering using Citric Acid and comes in I think 450cc bottles and dilutes down to 1-64. Be careful of the concentrate it is very caustic. First Call also sell a reasonably priced acetic acid based concentrate.

[Reinhold]

This was discussed back here...
http://www.film-and-darkroom-user.or...light=reinhold

Reinhold

[Miha]

Adrian, do you store it diluted (1+19)?

[photomi7ch]

I have had the same thing happen. As suggested by others I filter it and keep on using it till it happens again or runs out of steam. If I'm in a hurry I bin it for a fresh batch. For what it costs it is not worth mucking about really.

[Adrian]

Thanks for the replies. So no quick fix other than filtering it or keeping it concentrated and just making up the dilution when needed.

Yes it's the citric acid based stop from Ilford. I do store it diluted to 1:19. I hate the smell of acetic acid so I'll put up with the fungus.

[Miha]

Originally Posted by Adrian

I do store it diluted to 1:19. I hate the smell of acetic acid so I'll put up with the fungus.

I see this as a combination of several factors; I assume you are reusing it so each time you introduce some gelatine to the bath which microorganism adore. Some other makes include small amount of biocide, most often 2-Methylisothiazol-3(2H)-one but Ilford doesn't. I would recoment using it one shot and discard it after use.

[Martin Aislabie]

I never bother storing dilute Stop, unless I'm using it again next day.

Its "cheap as chips" - as the say and not environmentally harmful.

If your workflow is not very great on any one day, you can reduce the dilution, I go as far as 1+40 - but only if I'm using it for two or three films.

Acetic Acid stop bath is more bio resistant but smelly - so take your choice.

Martin

[John King]

The one and only time I had to deal with Stop Bath Fungus was in a Nova Deep-tank which I used for RA4 Processing, but as I said before once I went back to Acetic acid the problem ceased.

[Reinhold]

I also found a discussion by Riujii; "What is stop bath for?".
Things most of us never thought about...

I when printing, I like the Boric acid stop mentioned in the text .

Reinhold