Glacial acetic acid for prints?

[mfohl]

Not so much dangerous as inconvenient and requiring a lot more care. I imagine it wouldn't be that hard to dispose of if you could neutralize it, but I don't know how much base that would take or how much mess it might make. A few cases of baking soda and....

That would be exciting ....

 

[mfohl]

My favorite mnemonic device is no longer politically correct but no one has come up with a better one. "Bad Boys Rape Our Young Girls But Violet Gives Willingly." It gives the color code for resisters and capacitors: black = 0, brown = 1, red, orange, yellow, green, blue, violet, gray, white = 9. Learned in an all male engineering class.

Ah yes, young high school nerds. I was one of those once ...

PS - how many folks know what resistors and capacitors are

 

[bdial]

Certainly do use it!

You don't want to have to dispose of a gallon of glacial acetic acid. You may have to pass what you have left on to others when you pass on... A gallon will last practically forever!
...

Doremus

A camera shop that was closing up () gave me two gallons a few years ago. They did ask me a couple of times... "You know what this is, and how to deal with it right??"
I've managed to give out and use about 1/2 of the first one so far.

Fortunately, I don't mind the smell of acetic acid stop.

 

[DREW WILEY]

Roger... dye transfer printing uses a LOT of acetic acid, so I keep glacial around, even though at the moment I have no actual time for dye
transfer work. And any highly dilute acid is useful for neutralizing efflorescence on old concrete slabs, like my shop floor, prior to repainting. And stop bath is a helluva lot safer than muriatic. ... and even safer than getting caught swiping some of my wife's kitchen vinegar !

 

[Rudeofus]

My understanding is citric acid is a stronger acid than acetic. Depending on concentration and other ingredients a citric acid stop bath will have a lower pH than an acetic acid stop. This may or may not be relevant depending on the process.

As far as stop bathes are concerned, Citric Acid is a completely different animal compared to Acetic Acid. Citric Acid has three protons with pKa1=3.15; pKa2=4.77; pKa3=5.19. As a result you get very low pH with concentrated Citric Acid (which can hurt your photographic material) and rather poor buffering with more dilute Citric Acid (as found in most "odorless" stop bath formulas). And Citric Acid is food for mold, so you can't store a used stop bath unless you add a fungicide. Acetic Acid, on the other side, makes a very nice buffer between pH 4 and 5, right where we need it, and is a fungicide by itself. It smells, though ...

 

[Rudeofus]

Rudeofus - interesting info thanks for this. Can you elaborate on acetic acid buffering between pH 4-5? I'm not sure I follow.

If you slowly add an alkali (e.g. lye) to Acetic Acid, you will start with a very low pH which very quickly goes up to around 4, then slowly moves up to about 5 (and it takes a fair amount of alkali to get there), then after about pH 5.5 additional alkali will raise pH quickly again. With Citric Acid you will see three such steps, and the first step is too low for us (somewhere between pH 3 and 4), the second one would be sort of alright, and the third step is already in the pH 5.5 - 6 region where some development agents already become active. So as far as buffering is concerned, we use one of the three protons of Citric Acid (or two of the three in dilute Citric Acid).

Now to the difference between buffered and unbuffered stop bathes: an unbuffered one has to be dilute, otherwise its pH would be too low. As a result it doesn't last very long before its pH rises too high for proper stopping action. Each print carries a fair amount of developer which is quite alkaline (Dektol 20-30 g/l Na2CO3 and 10-20 g/l Na2SO3 depending on dilution). With a buffered stop bath you can use much higher concentrations of acid because you add alkali upfront to move pH into a region that is healthy for photographic material. As a result, it will sort of last forever.

 

[Roger Cole]

So the bottom line is that citric acid stops don't last as long? That's ok with me - still cheap. I use the indicator ones - is the indicator still an effective, well, indication?

I have noticed glop, presumably fungus, growing in old bottles of citric acid stop which I've had to throw out though, even concentrate that was pretty old.

 

[DREW WILEY]

Roger - you can filter out the water mold with a coffee filter, or perhaps add a bit of Listerine (thymol) to it to begin with. But isn't old stuff fermenting in jugs what you folks down there do for a little side money?

 

[Rudeofus]

So the bottom line is that citric acid stops don't last as long? That's ok with me - still cheap. I use the indicator ones - is the indicator still an effective, well, indication?

A indicator tells you whether pH has gotten above a certain level and should work regardless of which acid you use (assuming reasonable choices).

I have noticed glop, presumably fungus, growing in old bottles of citric acid stop which I've had to throw out though, even concentrate that was pretty old.

My biggest qualm with mold is that it reeks. If we use Citric Acid, with all its disadvantages, because it is "odorless", then moldy Citric Acid stop bath is completely pointless IMHO.

 

[Photo Engineer]

If you get mold in a CA stop bath it can "infect" the paper if any of the mold spores get left in the paper after washing. This is a Very Bad Thing.

Among methods to prevent this is the use of benzoic acid in the CA bath and/or formalin.

Don't let it grow and if it grows don't use it. You cannot filter out the spores!!!!!

PE

 

[dynachrome]

This is one of my oldest stories. Near the end of High School, many years ago, I thought the gallon container of glacial acetic acid in the science lab was getting lonely. It was nearly full and the bottle was made of very thick glass with a large cap. I brought it home on the subway (NY). It just sat on the floor between my legs for the whole trip. It was late enough in the year that the trains were no longer putting out any heat. A gallon of glacial acetic acid can last for years but not forever. If someone tried this today on a subway he'd get locked up for a good long time.

 

[mfohl]

This is one of my oldest stories. Near the end of High School, many years ago, I thought the gallon container of glacial acetic acid in the science lab was getting lonely. It was nearly full and the bottle was made of very thick glass with a large cap. I brought it home on the subway (NY). It just sat on the floor between my legs for the whole trip. It was late enough in the year that the trains were no longer putting out any heat. A gallon of glacial acetic acid can last for years but not forever. If someone tried this today on a subway he'd get locked up for a good long time.

Terrorist!