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EdmundH
6th September 2017, 02:57 PM
The mould growing in the stop bath slot of my Nova print processor is becoming a real problem, so I shall have to change to an acetic acid stop .
Some time ago I was given a very old glass bottle of 'Glacial' acetic acid. Can anyone tell me the correct dilution?

John King
6th September 2017, 08:28 PM
The actual dilution cannot be gauged unless we are aware of the actual concentrate you have. Some of the proprietry stop baths such as that by Kodak have a dilution of 1-73 whilst some others as little as 1-10.

On the back of this and acetic acid being quite dangerous in concentrates I would just put it back and get some of the better known brands. (Even the Kodak 1-73 version is very strong and pungent). AG sell one that is very cheap for 1 ltr but is clear and doesn't have the indicator if it is exhausted, however if it is replenised after each session, there is no need to have the indicator.

Mike O'Pray
6th September 2017, 10:09 PM
Do a google on glacial acetic acid, Edmund, to see what the range of concentrate might be. If it is almost pure glacial acetic acid then it might be as high as 99%. If it were this high then it freezes at about 16 degrees C. Most photographic high concentrate acid is about 28% acid. As John has said the stuff in its genuine glacial state can be very dangerous if handled carelessly. I would not want this stuff in the house nor anywhere near kids if it is genuine glacial acid. I'd want it under lock and one key to be retained by me at all times. I'd also want to reduce all of it to "safe" proportions (28%) immediately or find a way of disposing of it safely immediately on its glacial state.

I appreciate however that it might seem a shame to not use the stuff. If it were me I'd want to find out what percentage I was dealing with first and then I'd wear rubber gloves that came beyond my wrists with a long sleeved garment on and safety glasses and mix it outside on concrete with a hose at the ready in case of spillage.

Check which needs to be added to which i.e. I think it is acid to water and not water to acid to avoid any chance of splatter but again DO read up on the stuff and its mixing before trying anything.

It may not be illegal to have glacial acetic acid yet as an ordinary householder but I suspect if the police were to find out you had the 99% pure stuff,if that is what it is, then you might get a visit owing to the recent increase in "acid attacks"

Mike

Jerry Bodine
6th September 2017, 10:25 PM
Diluting it 3 parts acid to 8 parts water will create photo grade 28%. For use as a stop bath the 28% product is further diluted. Kodak has discontinued their 28% version quite some time ago and now offer only Indicator Stop Both (which is yellowish when freshly mixed but turns purple-ish when approaching exhaustion). Their recommended dilution to make a working solution is 1+63. I can no longer find any of their information on diluting the 28%, but when I used it for many years I always followed directions and diluted it 1+30 for both film and paper, with no issues.

PLEASE NOTE: The glacial version is extremely hazardous to handle. It is corrosive and dangerous healthwise. Here is the MSDS:

https://www.emdmillipore.com/US/en/product/Acetic-acid-%28glacial%29-100%25,MDA_CHEM-100063#anchor_Safety%20Information%20according%20t o%20GHS

I used a glass jug of it when I first stated photography and decided it was not worth risking any longer.

Jerry Bodine
6th September 2017, 10:35 PM
Mike, you are quite correct about the mixing. It is most definitely "acid to water" for proper mixing. I still recall from a looooong time ago my high school chem teacher drilling that into us, saying the easy way to remember it is "acid to water - that is Aw Wight".

BTW, I'd worry about storing the glacial in a glass container as the high freezing temp could lead to breakage and causing an awful mess.

Martin Aislabie
7th September 2017, 12:33 PM
Remember the acidic level of stop bath needs only to very slightly acidic.

If the acid level is too high you risk emulsion damage to your films as strongly acid solutions can cause photographic emulsion to "out gas" - you sometimes hear it on FB paper and see a tinny stream of bubbles being emitted.

On film emulsion, a strong acid stop bath can cause the emulsion to flake off.

Acid stop baths from companies like Ilford use buffering to maintain a suitable level of PH across a long usable life.

My advice would be to buy some proper stop bath with an indicator included and safely dispose of your glacial acetic acid.

Martin

EdmundH
7th September 2017, 03:41 PM
okay, I can see a general consensus here. It's only a small bottle, well hidden away. However I'll look out my Hazmat Suit at the weekend and diute/dispose of the stuff :}

John King
7th September 2017, 04:14 PM
Having just checked the usage of Acetic acid (not photographic use) it also states that if it is a heavy concetration (above 50%) it is advisable to also wear breathing aparatus as well as gloves etc.

JimW
8th September 2017, 04:21 PM
However I'll look out my Hazmat Suit at the weekend and diute/dispose of the stuff
NBC suit surely?:rolleyes: And best find out where/who can take it - some kid wandering over a landfill site and sorting through the junk finding it.....? Just thinking.

Lostlabours
11th September 2017, 09:41 AM
Ilford recommended:

IS (Ilford Stopbath)

17ml Glacial Actetic acid
Water to make 1 lire

This should have a pH of around 2.9/3, use until the pH level reaches 5.8, you can test with narrow range pH papers.

A Citric acid stop bath has a pH of about 4 in use but pH 1 when concentrated (modern citic acid based Ilfostop).

Ian

MikeHeller
11th September 2017, 02:44 PM
When I used to liberate glacial acetic acid from work for photographic use, I seem to remember I used it at 2% solution and single use; it was in the days before I had a toaster. My 1966 edition of Ilford Manual of Photography says 1%.
Mike

Lostlabours
11th September 2017, 04:25 PM
When I used to liberate glacial acetic acid from work for photographic use, I seem to remember I used it at 2% solution and single use; it was in the days before I had a toaster. My 1966 edition of Ilford Manual of Photography says 1%.
Mike

The Ilford IS-1 stopbath is in your Ilford Maunal of Photography :D

Ian

MikeHeller
12th September 2017, 04:18 PM
The Ilford IS-1 stopbath is in your Ilford Maunal of Photography :D

Ian

Ah, yes. 1.7% glacial acetic acid!!
Mike

Stocky
14th September 2017, 12:21 AM
Ryuji Suzuki posted (I don't remember where) a buffered acetic acid stop bath with adequately low pH but not particularly low. The alternative formula using 90% acetic acid and sodium hydroxide (both dangerous if mishandled) would be cheaper than sourcing sodium acetate. I haven't tried it (I use bisulphite stop in my Nova). His comment about the inconvenience of draining the Nova is because he was using the early simple one with drain outlets not at the bottom.

=======start of pasted article:

buffered stop bath (replenishable)
Written by Ryuji Posted: 06:09 AM - 01-19-2005

acetic acid, 90% 20ml
sodium acetate 80g
water to make 1.0 liter
target pH 5.0 plus/minus 0.5

same thing can be made this way:
acetic acid, 90% 60ml
sodium hydroxide 25g
water to make 1.0 liter
target pH 5.0 p/m 0.5

Either bath can be replenished at the rate of 30 ml glacial acetic acid per each 30 of 80 sqi processed. Buffered stop bath may appear more expensive but lasts MUCH longer than 1.7% acetic acid bath. The replenishing capability is very useful for Nova slot processor because changing the entire bath is a real pain in that processor.