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citric acid

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CMoore

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Joined
Aug 23, 2015
Messages
6,347
Location
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The last few days i have been reading about Stop Baths.
At this point i am mainly using ID-11 developer and FP4 or HP5 film. Will no doubt be using Ilford multi grade paper as well.
Anyway, from my reading, it seems to be as simple as buying (which i have) some citric powder, and adding a bit to some water.
Is that really all there is to it.? Just mix up a bit and toss it out after it sits for a few days.....just those two elements.?
Thank You
 
Yes, citric acid provides an odorless stopbath. It is used as a 1% solution for films and papers.
 
A teaspoon full in a couple of litres of water is my mix. Buying citric acid in bulk makes it a very low cost stop bath - I also toss it after each session and don't bother keeping it to use another day.
 
OK... i will do the same, and just toss it out at days end.
Thank You
 
For film, mix it as indicated and use it essentially one shot.

For prints (especially fibre prints), you want to pay closer attention, because citric acid stop bath (like all stop baths) will lose effectiveness as developer is carried over into it. That is why manufacturers add an indicator to stop bath - an additive that changes colour when the stop bath requires replacement.

Any suggestions for CMoore what print capacity a teaspoon/2 litre batch of citric acid stop should have?
 
I've been using citric acid stop for years now. There's a wine making supplier just down the road from me that sells it cheaply in 1kg bags. One heaping tablespoon per litre does it for me. I also use it for kallitype printing.
 
For some reason every year or so I run into someone cleaning out a darkroom. I have conservatively at least 7 or 8 bottles of stop bath. Last couple times I've gotten the nice Ilford indicator citric acid stop. Since I will be dead before I use all my Kodak indicator stop, I just may give the ilford a go. I mixed up some of my free regular Kodak f-5 powdered fixer, wow I have forgotten how much that stuff stinks!
Best regards Mike
 
If you are concerned about the acidity of a citric acid stop bath just get a vial of blue litmus or congo red paper and test it a couple of times during a print session.
 
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As long as you either tally the number of prints run through your stop bath or use an indicator you'll be fine. In my experience a tray of acetic acid stop bath works for all of one of my sessions but citric acid stop doesn't seen to have quite the same capacity. So I either use a deep tray and twice as much stop or dump and mix fresh at lunch time.
 
Supermarkets also have citric acid. It's used in some sort of cooking (maybe jam making?)
 
Health food stores always have it in bulk. I think I pay $6 a pound here in Fl. at a Richards. I don't use stop bath for film (no need) but for prints I just throw two heaping teaspoons in a tray and if I am in the darkroom long enough I throw in another teaspoon. No math needed. If I remember correctly, Citric acid is not as strong as Acetic acid, so too much is mostly going to be ok, unless you are in the waaaaay too much category with film.
 
Health food stores usually carry it. As a general word of caution -- be careful not to buy anything that has extra additives. Some years ago an ApUGER bought some ascorbic acid that contained 5% powdered rose hips. While it worked as expected he had to filter off the rose hips each time he made up a developer. So always check the label.

update: My original post was not too clear. The ascorbic acid example was a caution about adulterated products in general.
 
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mehguy said:
Where can I get citric acid?
Click to expand...

Fleabay, many options wrt quantity. iirc, I got a kilo for about £5 delivered. Homebrew shops usually carry it but often only in 100g/4oz containers.
 
Citric acid is also know as sour salt, you can find it in the canning section of a supermarket or megamart especially this time of year (canning season). I've also found it in the Kosher food section of stores.
 
Interesting thread. I found a german vendor on ebay that sells both Citric acid and Sodium bicarbonate. I can use the acid for stop bath and the bicarbonate for my stomach. A teaspoon before bed so I can sleep. :sick:
 
Patrick Robert James said:
Citric acid is not as strong as Acetic acid, so too much is mostly going to be ok, unless you are in the waaaaay too much category with film.
Click to expand...

As a chemist I know this statement should be the other way around. Acetic acid is weaker. You can look up the ka constants for acetic and citric acids. There are three constants for citric acid since it contains 3 -COOH groups. Acetic acid is considered to be a weak acid while citric is a moderate strength one.
 
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darkroommike said:
Citric acid is also know as sour salt, you can find it in the canning section of a supermarket or megamart especially this time of year (canning season). I've also found it in the Kosher food section of stores.
Click to expand...

Sour salt (citric acid) is rather pricey for the amount that you get in a typical bottle in the Kosher food section.
 
If you have some surplus citric acid, mix it equal parts with sodium bicarbonate and white/icing sugar. A fizzy type of sherbet that amuses kids for a while.
 
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