Pre wet colour paper with a jobo drum. Yes or no?

[Don_ih]

the cheapest vinegar around her worked out to be more expensive per use than stop bath

one can use stop bath with indicator many time with color paper and that will work out to be much cheaper than using vinegar as a one shot stop bath.

I bought 4 litres of vinegar for $1.49, yesterday. Stop bath is $10 per half litre.

Arguing against the use of vinegar as stop bath is silly.

Pre-wetting gets the drum, the paper, and the air in the drum up to working temperature. If you don't mind your developer temperature dropping by 10 degree C when you start developing, then don't pre-wet. Some people develop at room temperature and get good results.

 

[MattKing]

Stop bath is $10 per half litre.

If that is the Kodak stuff, it will make 32 litres of working solution - about $0.30 per litre.

I bought 4 litres of vinegar for $1.49, yesterday.

If that needs to be diluted 1 + 1 to get to working strength, it will make 8 litres of working strength - about $0.16 per litre.
Vinegar is cheaper than it used to be. Stop bath is a bit more expensive than it used to be, so the savings aren't where they used to be - except for the space savings.

 

[DREW WILEY]

Most stop bath formulas call for 2% acetic acid. That's probably with re-use in mind. But it's way too much for one shot use, where 1/2% is adequate. I just keep gallon jugs of glacial acetic acid on hand. Yeah, you gotta be careful handling it and with the fumes until diluted; but one of those gallon jugs will make a helluva lot of working strength stop bath quite economically.

 

[Don_ih]

If that is the Kodak stuff, it will make 32 litres of working solution - about $0.30 per litre.


If that needs to be diluted 1 + 1 to get to working strength, it will make 8 litres of working strength - about $0.16 per litre.
Vinegar is cheaper than it used to be. Stop bath is a bit more expensive than it used to be, so the savings aren't where they used to be - except for the space savings.

I doubt Kodak stop bath is 160% acetic acid....

 

[MattKing]

What percentage is your vinegar?
According to the MSDS, the Kodak Indicator Stop Bath is "more than 80% by mass" glacial acetic acid.

 

[Don_ih]

What percentage is your vinegar?
According to the MSDS, the Kodak Indicator Stop Bath is "more than 80% by mass" glacial acetic acid.

Vinegar is 5% acetic acid.

To achieve a dilution of 2.5% at 32 litres, the half litre would need to be 160% acetic acid. Perhaps you meant a litre bottle? That accords with 80%.

Anyway. Cost needs to take in more than just unit price. The convenience of getting cheap vinegar makes it much more appealing. Also, if you use your stop bath until it turns purple, you've used it for far too many sheets, anyway. (Who would reuse diluted stop when developing film?)

 

[MattKing]

Vinegar is 5% acetic acid.

To achieve a dilution of 2.5% at 32 litres, the half litre would need to be 160% acetic acid. Perhaps you meant a litre bottle? That accords with 80%.

Anyway. Cost needs to take in more than just unit price. The convenience of getting cheap vinegar makes it much more appealing. Also, if you use your stop bath until it turns purple, you've used it for far too many sheets, anyway. (Who would reuse diluted stop when developing film?)

I'm not saying that vinegar isn't a viable option now - I'm saying that there are pros and cons with using it instead of indicator stop bath, and while the price is now similar, that wasn't necessarily the case when vinegar was more expensive!
White vinegar is one of the few products that has gone down in price - significantly!
But those 4 litre bottles haven't got any smaller.
I reuse Kodak stop bath for film when I'm doing several batches of development in a day or two. Otherwise I use it at half strength, and discard after use.
If I could find equally well priced glacial acetic acid in easy to handle, safe half litre bottles, I would consider replacing the indicator stop with that.
But I do like having it as a backup, for the citric acid based indicator stop that I use when printing.

 

[Don_ih]

citric acid based indicator stop

That stuff (at least what I have) seems to be too expensive. I have a small bottle of Fomacitro. I think the dilution is 1:19? Maybe. Whatever it is, to fill a tray for printing uses 1/3 of the bottle.

 

[DREW WILEY]

Kodak Glacial Acetic Acid is nearly 100% acetic acid and is classified as a hazmat item. Indicator Stop Bath is only 28% actual acetic acid, plus a litmus dye. Vinegar varies, but is weaker than either. I certainly wouldn't want to substitute Indicator Stop Bath in an oil and vinegar salad dressing!

 

[MattKing]

Indicator Stop Bath is only 28% actual acetic acid, plus a litmus dye.

80% by mass, according to the current MSDS.
Don't spill drops of it on a laminate countertop - I learned this the hard way..
The 500 ml bottles of citric acid based Ilfostop dilute to 10 litres (1 +19), which is enough for 5+ printing sessions for me.
I keep a pound of citric acid powder from a U-brew source in backup - in case I run out of Ilfostop.

 

[DREW WILEY]

If it were 80% by solution, Matt, it would be almost as hazardous as glacial acetic, and be un-shippable except hazmat. I'm well aware of what MSDS sheets are. We had an entire library of them in our Govt and Military sales dept right down the hall from my office before there was easy access over the web. In other words, it's not 80% acid, 20% water, but only 28% diluted acid plus an equivalent molecular weight of only 20% added "ingredient" such as litmus dye. I've got both styles or concentrations on hand, and there is an enormous practical difference between them. Even a small spill of anything even close to glacial purity, like 80%, and you'd have to immediately leave the room or risk lung damage. I only dilute it down myself under a powerful fume hood. Indicator Stop is far less noxious.

Actually, the current MSDS listing gives Indicator Stop as 80-90% "component" = acetic acid. That term "component" is significant because it is attached to any ingredients having an applicable CAS registry number, in other words, what must be identified as an active ingredient required to be disclosed for safety reasons. Added water is NOT one of those. Even the dye does not need to be specifically identified in this particular case.

Compare Muriatic Acid, which is typically 18% hydrochloric, but still needs massive dilution for swimming pool use. The other 82% is water, which is not one of the "active" ingredients, so is not considered as MSDS significant. Anyway, the actual concentration of acid in Indicator Stop Bath is listed right on the bottle label, or at least used to be. I still have only the old style bottles.

 

[BMbikerider]

You can eliminate the need for pre wetting film or paper before developing by adding one small drop of wetting agent to the developer. That destroys any surface tension and lets the water flow freely over the material. When I say 'small' drop I mean no larger than a match head. We always used to do it when I was in the forces overseas especially in the Mediterranean and middle east areas where the daytime temperature in our darkroom would get to over 130F.
It also had it would appear the advantage of stopping any grit or hairs attaching them selves to the emulsion when it is wet and soft because that was a problem we never had to deal with.

Water on it's own will not 'dilute' colours, colour emulsion will not react to plain water it has to have some reagent such as the developer or blix added.

 

[xkaes]

I always pre-wet. That not only helps the developer spread more evenly afterwards, but helps to precondition the inside of the drum and paper surface itself to the correct temperature.

I use Colourtronic tubes in a heated water bath and always pre-wet for all the reasons listed above -- to avoid problems. Never had any complaints.