Experiences with Vitamin C developers please

[Gerald C Koch]

Using carbon dioxide to preserve developers is not a good idea. It will lower the pH of ordinary developers. It is also not necessary with waterless concentrates made with TEA or glycols. Carbon dioxide will form an adduct with TEA which will lower the pH when water is added. However it is very doubtful that enough carbon dioxide is absorbed to realistically change the pH of these concentrates.

As has been stated many times measuring the pH of distilled or de-ionized water is rather pointless as purified water has very little buffer capacity. This means that the pH is easily changed by VERY small amounts of acidic or alkaline additions. Even carbon dioxide from the air will change its pH. It also means that its pH is changed by the chemicals added to make a developer.

There is a fundamental problem when ascorbate is used as both a developing agent and as a preservative. As ascorbate is used up in its role as preservative the amount available as a developing agent also decreases. This is not a problem for sulfite based developers such as D-76 .

 

[sfaber17]

This might make another reason for mixing the developing agents in glycol which I measured at a pH of 5.5 which couldn't care less about a blanket of CO2 I should imagine...

I'm doubtful that you could use a glass pH electrode to measure pH accurately in glycol.
I tend to agree with Gerald's discussion though about CO2 not having much effect on the TEA.

I agree with you on using 510-Pyro at high dilutions. I wouldn't do it with rotary processing. Maybe
with stand development with large volumes and small amounts of film.

I did do a test developing a 4x5 sheet in a tray at 7.5 min 23C to compare with rotary processing, and the result
was a CI of .42 in the tray vs the .48 or so IIRC in the jobo. The spent developer was about the same color as with the jobo also, so the conclusion is that the jobo isn't over-oxidizing the developer from aeration, and the CI difference can be accounted for by the difference in agitation.

 

[swmcl]

Sorry ... I've just realized it wasn't CO2 I was using but N. I've been using a hand operated air duster to squirt some Nitrogen onto the tops of my various chemicals in solution. The reason I got confused was I did actually buy a 6-pack of CO2 canisters intended for the aquarium industry but then changed over to Nitrogen.

I trust Nitrogen is no worse than CO2.

 

[Gerald C Koch]

Nitrogen is essentially inert under normal conditions and would have no effect on photo solutions.

 

[Rudeofus]

Is there a significant difference in diffusion speed (through bottle wall materials) between Nitrogen, Carbon Dioxide and Butane?

 

[swmcl]

I should mention that I only recently switched over to N2 - so the previous post of mine is relevant up to a few months ago. Previously I had used several canisters of CO2 (hence my confusion) and certainly my first batch of 510 Pyro was under CO2.

My chemicals are stored in amber glass bottles with those black phenol ? lids that screw down tight and are kept in a fridge. No diffusion, high temp or sunlight allowed !

 

[Paul Verizzo]

Sorry ... I've just realized it wasn't CO2 I was using but N. I've been using a hand operated air duster to squirt some Nitrogen onto the tops of my various chemicals in solution. The reason I got confused was I did actually buy a 6-pack of CO2 canisters intended for the aquarium industry but then changed over to Nitrogen.

I trust Nitrogen is no worse than CO2.

If you are referring to "canned air", it is not nitrogen. It is of the Freon family. Another thread closeby shows that it does change the activity of Xtol, oddly enough.

Plain old propane or butane does the trick fine. The Tetenal product is ORM-D (haz mat category) That tells you right there what it most likely is.

 

[Gerald C Koch]

The problem with using nitrogen is that it is slightly lighter than air. So getting it into a bottle is the trick.

The best way to prevent oxidation is to store developer in several fully filled bottles and to use it promptly once a bottle is opened.