CD-4 in glycol

[bnxvs]

Hi there!
Please tell me - what is the maximum concentration of CD-4 in glycol can be achieved? I want to make long-life concentrates. 4.5 g are successfully dissolved in 25 ml of propylene glycol. Is it possible to dissolve more qty. of CD-4... for example 40-50g per 100ml of PG? I don’t have many CD-4s and I’m afraid to risk spoiling the latter. Maybe someone has experience in this matter?

 

[Rudeofus]

I highly recommend you try making such a concentrate in very small amounts at first. I did make such a CD-4 concentrate in TEA a while back, and it turned dark purple very quickly. Lack of water does not automatically make such a concentrate long term stable!

Once you are sure your concentrate is long term stable, you could go the opposite way: start with some amount of CD-4 and PG, and if it doesn't all dissolve, incrementally add more PG until is does. Find some way to heat the PG (e.g. with a hair dryer or some heat blower), this will speed up dissolution process a lot.

 

[bnxvs]

Thanks for your advice. I'm still watching a small amount of CD-4 solution in PG. If there are no changes in a few days, I’ll try to perform an experiment with a high concentration.

 

[Photo Engineer]

It is the Oxygen in air that is the danger. That is why commercial kits are packed with some form of Sulfite.

PE

 

[bnxvs]

It is the Oxygen in air that is the danger. That is why commercial kits are packed with some form of Sulfite.

Glycol isn't water. There are many examples showing that it doesn't so actively absorb oxygen from the environment. And as Patrick Gainer convincingly proved: sulfite - sucks)))

 

[Rudeofus]

Sulfite/Metabisulfite is actually the preservative to keep CD-4 in shape in pretty much any C-41 kit, it works quite well if done correctly. The biggest issue will not come from dissolved Oxygen, but from Oxygen at the solution surface. CD-4 can and will oxidize there at this surface, and diffusion will see to it that every CD-4 molecule gets to meet its fate over time. Therefore I recommend you don't commit too much CD-4 to this at first - once you know it lasts you can always mix more.

 

[Anon Ymous]

I don't know if it says much, but the CD4 I bought two years ago hasn't change colour and is still slightly off white. I keep it in a small glass jar with a lid that closes tightly. I don't see the point in dissolving CD4 in an organic solvent. Am I missing something?

 

[koraks]

Mixing a working solution from a liquid concentrate is a little easier and quicker than weighing out the dry stuff in my experience, so I assume that's the background to this thread as well.

But CD3 and CD4 just don't keep well as solutions, at least not in the kind of solutions and packaging conditions we can realistically achieve in a home darkroom setting. If glycol were the solution, I'm sure several commercial C41 developers would have employed that approach.

I'll be following this thread with interest to see how it pans out. My brief experiments with concentrated stock solutions of CD4 were very disappointing to say the least. I've rarely seen stuff oxidize so fast, even though it keeps formidably well in dry form.

 

[bnxvs]

I'm planning to monitor the status of the solution for about 15 days. Then I'll do a control development. If everything will be OK, I'll do the second test in 30 days.
Stock up on popcorn

 

[koraks]

Stock up on popcorn

Will do! My tests with aqueous concentrates gave severe oxidation after only a day or 2, so 15 days would already be quite an improvement!

 

[Rudeofus]

Will do! My tests with aqueous concentrates gave severe oxidation after only a day or 2, so 15 days would already be quite an improvement!

That's strange. Was this CD-4 alone, or with a trace of Sodium Metabisulfite? AFAIK concentrates for C-41 CD and E6 CD work just like that and last for a year or more.

 

[koraks]

Just CD4 and CD4 acidified with acetic acid. I didn't pursue the metabisulfite route. AFAIK commercial concentrates of CD4 are packaged in a protected atmosphere (no oxygen in the bottle) and with dissolved sulfite. The latter is easy, the former is a bite more difficult. I didn't pursue the issue simply because I didn't find it worth it; weighing out the dry stuff, while slightly more work than using a concentrate really isn't all that much work.

 

[GLS]

I don't see the point in dissolving CD4 in an organic solvent. Am I missing something?

Because the solubility of oxygen in many organic solvents is lower than it is in water, thereby providing more protection from oxidation of the developing agent over time. This is the reason some developers (such as Pyrocat-HD) use glycol as the solvent for part A.

 

[Anon Ymous]

Because the solubility of oxygen in many organic solvents is lower than it is in water, thereby providing more protection from oxidation of the developing agent over time. This is the reason some developers (such as Pyrocat-HD) use glycol as the solvent for part A.

Yes, I know about that, I just don't find much use in doing so. Had it been a case of using a very small amount of a compound, then it would be practical to do so. In this case, we're talking about using something like 5g/l, easily weighed and accurately. And as I said, CD4 keeps well in powder form in my experience.

 

[Photo Engineer]

That's strange. Was this CD-4 alone, or with a trace of Sodium Metabisulfite? AFAIK concentrates for C-41 CD and E6 CD work just like that and last for a year or more.

C41 and E6 concentrates contain Sulfur Dioxide in acid to scavenge Oxygen and insure keeping.

PE

 

[bnxvs]

the third day

In the right glass of CD-4 (the color has not changed at all). In the left glass are all the other ingredients. This volume is designed for 1 liter of finished developer. To be continued...

 

[koraks]

The solution on the right has oxidized to such an extent that I personally would not consider using it.

 

[bnxvs]

You are inattentive. I wrote - "the color has not changed at all." This is a concentrated solution of CD-4 in glycol, and it initially has such a red color.

 

[Rudeofus]

There's a non-trivial chance, that the CD-4 has already oxidized as powder before you dissolved it in Glycol. I would not worry about this level of discoloration, but expect more during the next few weeks/months. Is my assumption correct, that this is roughly 5g of CD-4 in 50ml Glycol?

 

[bnxvs]

Yes, there are about 5 grams. But this CD-4 is fresh.
It doesn't such colorize when dissolved in water. This occurs exclusively in PG, the solution immediately acquires the color of "young wine". I'll be waiting 15 days, as planned, before I try this solution in work. I think that you're worried about the color in vain.

 

[halfaman]

A standard CD-4 kit concentrate bottle last one month opened easily. If glycol has any advantage compared to standard water formula it should surpass that mark clearly.

 

[Photo Engineer]

I've had them last at least 6 months.

PE

 

[bnxvs]

7 days ))) (1-th test)
Fuji Superia 200 (2014 exp.). DIY rotation machine (based on Agfa Rondinax)

 

[Rudeofus]

Nobody expected much of a change after 7 days of storage. Here is a thread about someone reusing working solution over three months and still getting scannable negs. If a CD-4 concentrate is not able to last for at least 6 months, it's probably not worth mixing.

 

[bnxvs]

Nobody expected much of a change after 7 days of storage. Here is a thread about someone reusing working solution over three months and still getting scannable negs. If a CD-4 concentrate is not able to last for at least 6 months, it's probably not worth mixing.

You contradict yourself. You didn't like the color of the concentrate - so I did a test to show that there were no problems with oxidation. Now you are writing that 7 days is a short time for the test ... I have the impression that you just really don’t like this experiment of mine (I don't know why) and you're looking for a reason to declare it unsuccessful. Strange position.