Acetic acid as stop bath for film?

Necator · Oct 3, 2010

So far, when I have developed film, I have rinsed with water 4 times after development, instead of using a stop bath. However, as it takes me a while to hit the right water temperature from the tap, I end up wasting a lot of water (as I need to find the right temperature for making the developer, for the "stop" rinse, and for the final rinse). Therefore, I was wondering if I could use acetic acid (29% solution) as a stop bath? Would it work, and how much should I dilute it?

Ian Grant · Oct 3, 2010

Dilute about 1+30 to get a 1% (approx) solution, that's a good stop bath.

Ian

Removed Account2 · Oct 3, 2010

Methinks thts too little. The old X-rule suggest 2 parts of 29% acetic acid and 27 parts of water, which will yeld a 2% solution.

That was recommended as a stop bath back in the day. Just add 44ml acetic and dilute to 600ml for one Paterson tankful.

Ian Grant · Oct 3, 2010

Erik Prestmo said:
Methinks thts too little. The old X-rule suggest 2 parts of 29% acetic acid and 27 parts of water, which will yeld a 2% solution.

That was recommended as a stop bath back in the day. Just add 44ml acetic and dilute to 600ml for one Paterson tankful.

1% is fine particularly if it's going to be used once and discarded, for re-use 2-5% is more typical.

Ian

rufusm · Oct 3, 2010

Necator said:
However, as it takes me a while to hit the right water temperature from the tap, I end up wasting a lot of water (as I need to find the right temperature for making the developer, for the "stop" rinse, and for the final rinse).

I also do not have temp control on my tap, when I know I am going to work in my darkroom I fill a clean bucket with water a couple of hours before hand and let it get to room temp. No waste as I use it for film and paper chemistry and it's also enough water for the ilford 5-10-20 final film wash.

Anon Ymous · Oct 3, 2010

If you have 28 - 29% acetic acid, then you can make a 2% solution by using 70ml acid and topping up to 1 litre. This is reusable and its capacity is above 20 films (135, 120, 8x10, 80 square inches generally). Just make 1l and mark a line on the bottle for every film. The formula for SB1 (kodak) is a tad less than 1,5% solution and the stated capacity is 20 films per litre.

And since I mentioned the SB1 stop bath, the formula is 48ml of acetic acid 28% solution in 1l water. Rounding it to 50ml is just fine.

tomalophicon · Oct 3, 2010

Are you guys talking about using vinegar? Or a commercially available acid?

ic-racer · Oct 3, 2010

I'm not sure I'd use water for film stop. I like to have development stop on time. I use the 1.5% formula.

ic-racer · Oct 3, 2010

tomalophicon said:
Are you guys talking about using vinegar? Or a commercially available acid?

In the USA "white vinegar" is dilute acetic acid. The bottle my wife has says 5% so it can be diluted as needed.

dehk · Oct 3, 2010

I use cold water as 'stop bath' most the time just because I am lazy and it does work for me since its pretty cold coming out from the well. Alternatively I will use diluted White Vinegar especially when printing. And vinegar works great for me.

Ian Grant · Oct 4, 2010

dehk said:
I use cold water as 'stop bath' most the time just because I am lazy and it does work for me since its pretty cold coming out from the well. Alternatively I will use diluted White Vinegar especially when printing. And vinegar works great for me.

Any stop or rinse MUST be the same temperature as the Developer and fixer or you run the risk of grain clumping/micro reticulation, or worse still full reticulation. This is worse with some films like Fuji Neopan 400, and Tmax 400, or the EFKE & Foma ranges.

Ian

Necator · Oct 4, 2010

I will try with a 1+30 dilution, thanks.

panchro-press · Oct 4, 2010

The only concern you should have using a stop bath with film is in making it too strong. The stronger the acid, the greater the possibility of pin holes...especially with a carbonate type developer.

Dave

Ian Grant · Oct 4, 2010

panchro-press said:
The only concern you should have using a stop bath with film is in making it too strong. The stronger the acid, the greater the possibility of pin holes...especially with a carbonate type developer.

Dave

Hence the 1% rather than stronger

Ian

Removed Account2 · Oct 4, 2010

Hey Ian, that is a good tip, especially in connection to carbonates, since I develop a lot of film in Caffenol-C, which IS a carbonate developer.

Being extremely thrifty I also appreciate the fact that I can cut back on the acetic acid, and save 50% on that alone!

Also the reminder of keeping temperatures at the same level all through the process should be noted by everyone, thats why I wash the film in 6 succesive changes of water in the tank, instead of hooking it up to the icecold tap water (live in Norway.....) 6 changes equal a dilution of roughly 1/1000 000, which, compared to running water would require 100 hours or thereabouts....

Have a nice day.

ozphoto · Oct 4, 2010

I've used both water and vinegar as stop bath; both have worked well for me, but I'm currently using some indicator stop bath.
Any of these will work, it depends on what you can get your hands on at the time - hard to buy chemicals when the shops close over Christmas, hence good ol' reliable vinegar or water at a pinch.

clayne · Oct 4, 2010

Erik Prestmo said:
Also the reminder of keeping temperatures at the same level all through the process should be noted by everyone, thats why I wash the film in 6 succesive changes of water in the tank, instead of hooking it up to the icecold tap water (live in Norway.....) 6 changes equal a dilution of roughly 1/1000 000, which, compared to running water would require 100 hours or thereabouts....

Have a nice day.

Can you explain that last part? Surely you'll approach the same dilution (of something) with running water within similar volumes.

Ian Grant · Oct 4, 2010

G.I.P. Levenson at Kodak (Harrow, UK) came up with a number of changes of water giving optimal dilution of residual fixer. The assumption is that each dilution/change reduces the amount of residual silver/thiosulphate complexes that can be washed out to 2% of the previous level.

Over 6 changes it's actually more than the 1/1000,000 dilution Erik mentions. The problem with running water is it's hard to get efficient washing at the slow flow rate required to use the same amount of water, so typically 10 times or more water is used.

Ian

bsdunek · Oct 4, 2010

panchro-press said:
The only concern you should have using a stop bath with film is in making it too strong. The stronger the acid, the greater the possibility of pin holes...especially with a carbonate type developer.

Dave

That's why I quit using acid stop for films. I just use one tank of water for about 30 sec. Seems to do the trick for me, and my fixer lasts a long time, so I must not be hurting it. I think four washes is over kill - just IMHO.

Ian Grant · Oct 4, 2010

Here in Turkey I just use water for films, my fixer lasts just as long as when I use stop bath in the UK.

Ian

Removed Account2 · Oct 4, 2010

clayne said:
Can you explain that last part? Surely you'll approach the same dilution (of something) with running water within similar volumes.

I know nothing about your background, but to understand this you must study chemical engineering a liitle.

In a sense you're comparing apples with oranges.

Dilution is simple, you need X litres of water to achieve something, in this example 1000 000 litres of water. At half a litre per minute you can work out how long that would take.

The other technique uses a simple trick : every time we empty the tank (six times) we DISCARD 95% of the impurities, here sodium thiosulphate.

Then we dilute this to 1/20 by filling the tank. Repeated 6 times the calculation is a continued multiplication :

1/20 x 1/20 x 1/20 x 1/20 x 1/20 x 1/20 = 0.000 000 015

That means I was a little off, you need 66 666 666,67 litres plain dilution to achieve the same goal, and that is a LONG time at half a litre per minute!

A college course in chemical engineering cover this.

PS dilutions at this level is really meaningless, at 1/10 000 strength we're talking clean water already and the slightest trace of fixer on your hands will pollute the entire tank and throw all calculations to the wind.

I use 6 changes of water to be damn sure, Ilford states that 3 changes is enough.
Doubling the number of changes does not make me double sure, it makes me more than 1000 times sure and that concept is hard to grasp unless you study this a little closer.

Ian Grant · Oct 4, 2010

Remember that Kodak's longer wash cycle was based on using Sodium Thiosulphate fixer with a hardener, Ilford's on Ammonium Thiosulphate with no hardener.

Like you though I do five or six changes, and slightly longer than Ilford's times for each bath. Ammonium Thiosulphate and the silver complexes formed are more soluble than the Sodium equivalents.

Ian

clayne · Oct 4, 2010

Here's my issue. We're not filling an ever increasing lake of water when we use running water (rather than water changes) - so isn't the dilution comparison a bit off? If we're replacing water rather than continuously adding water to a tank that gets increasingly larger, I can't see how it would possibly take 66M liters of water to approach the same level of fixer dilution. When we use running water the tank is seeing a removal of old water and replacement with new just the same.

For the record though, I do use the Ilford method.

Removed Account2 · Oct 4, 2010

Nope your'e wrong its the hypo content in the FILM that is the contaminent.
If you discard six times its the same as filling the tabnk continiously with a million liters of water.....

This concept might be hard to grasp for somebody that hasn't studied chem. engineering, to cut a long story short : trust me - and Ilford!

clayne · Oct 4, 2010

And how is running water into the tank *not* discarding water? The tank volume does not expand.

Acetic acid as stop bath for film?

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