[RA4] Citric Acid Stop Bath?
I've read lots about using citric acid as a stop, but all the posts are in the B&W forums. This is just to ask is there any issues with RA4 processing?
I currently use white vinegar diluted 1:4 as a stop and that's fine. The problem is that my wife likes to use white vinegar for cleaning and we both blame each other when the stocks are low! Last night we had only a bit left and my stop was quite weak. I got horrible blue/green streaks on my prints and now I'll have to dump my blix which I'm not happy about.
Can I change over to a citric acid stop?
I wouldn't use citric acid stop bath.
I tried it in my Nova tank once (RA-4).
After several days, it was contaminated with what looked like some sort of scummy organic matter.
I used to buy glacial acetic acid from Rayco, but they went out of business some time ago.
It's pretty cheap and you only need 20ml/litre.
I'm not sure where you can buy glacial acid these days but you can buy 80% solution from places like ag-photographic or sliverprint.
My plan was to use it one-shot and chuck it out after one printing session (4-6 prints).
Steve I can't see why citric acid which works for B&W paper shouldn't work for RA4 unless there is something about the chemical properties of citric acid which fails to do the same job with RA4 dev. I would also have thought that if you can buy citric acid powder in bulk it would work out cheaper than white vinegar and be purer. It may be that white vinegar is pure but it may also contain ingredients that citric acid crystals do not.
For B&W the general amount is about 15g per litre. Homebrew shops used to sell it in large quantities.
I always use citric acid stop for RA-4 (in trays at room temp). Never had any problems with it.
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AFAIK, Citric Acid should not be used with color products.
Don't ask. That was a suggestion I had from years ago. I think it might be the lesser acidity of the Citric Acid in comparison to Acetic Acid.
IIRC the old Kodak Hobby Pacs for making prints (EP-2 process) used citric acid in the stop bath.
I am not aware that the hobby pacs had citric acid. If I have one here I will check, but IIRC, they were all liquid kits and did use acetic acid. I was called from Christmas vacation in 1968 to work on a fix for the process, and had to come up with a fix. We made several variants and the 1 - 2% acetic acid won out for quality.
Perhaps the citric acid works one shot, IDK, but the stop we designed was acetic acid.
You see, it must be strong enough to extract the color developer from the coupler droplets so that none is retained in the coating. If CD3 is retained, the dye stability is affected. Citric acid did not acidify or extract well IIRC.
Confused here: Kodak say you do not need any stop, but that you should use a rinse if you do use a stop with Kodacolor RA chemicals.
From Kodak pub. j39.pdf:
From which I assume that as long as you don't process too many sq inches of paper you should be OK without?
Optional Stop Bath and Wash
Excessive developer carry-over into the bleach-fix can cause
surface marks or streaks on prints. If this occurs, use a
30-second stop bath followed by a 30-second wash between
the developer and the bleach-fix.
To prepare the stop bath, use 28 mL of KODAK Glacial
Acetic Acid per litre of water.
I used the Pacs in the mid-eighties, it was the only chemistry I purchased then, and I remember the stop bath packet (liquid) saying it contained citric acid, but I could be mistaken. I didn't used them but threw them away and instead I just used acetic acid I already had mixed, so I don't know how well it would have worked, if that is what it was.