Oily substance in home-brewed C-41

[srs5694]

For a couple of years, I've been using this C-41 developer with good results. (Yes, I know it's not as close to Kodak's formula as some, but it's worked well enough to satisfy me.) Anyhow, my last couple of batches have produced an odd result: When I add the CD-4 as the last chemical, it begins to fizz and produces an oily brown substance that floats on the top of the solution. I've used the developer (with and without filtering this substance out), and it works, but the negatives seem a bit thin. (I have no quantitative measures with a densitometer, though; that's just my eyeball judgment.) The first time this happened I put it down to the fact that there was a bit of CD-4 that had clumped together; I figured there was an impurity that caused the problem. This isn't true of the last batch, though. I've got several hypotheses and was wondering if somebody might be able to rule any in or out, or suggest other alternatives:

• CD-4 gone bad -- My CD-4 is about two or three years old, so it could simply have gone bad.
• C-41 concentration -- I've been experimenting with C-41 concentration; for a while I've been mixing a 2x concentrate, but I've tried a 4x concentrate with these last two batches. Could the CD-4 be reacting when ingredients are at higher concentration even when it wouldn't react at lower concentration?
• Undissolved chemicals -- It's conceivable I just happen to have been less patient about dissolving other ingredients (particularly the hydroxylamine sulfate, the ingredient to go into the mix immediately before the CD-4) in these last couple of batches. Could the CD-4 be reacting with undissolved substances in ways it wouldn't be reacting with fully dissolved ingredients?
• Water impurities -- I use store-bought distilled water for my C-41, but I'm not picky about brands. Could I have a bad bottle of distilled water?

Any suggestions or tips are welcome. Thanks.

 

[Photo Engineer]

Are you sure it is CD-4? CD-4 is quite soluable compared to other color developers.

OTOH, at 20 g/l (4x concentration based on your formula), CD-4 in 4x alkali would probably oil out. It will almost always fizz as it is an acid salt and as such it reacts with the carbonate to give CO2 gas.

The formula, is not optimum in any case and gives no pH. Without that, if anything goes wrong who can say what it was from.

The blix formula is too weak and without extra EDTA will tend to stain the film orange which you will miss due to the orange mask.

PE

 

[srs5694]

Thanks; based on your second paragraph I'll try cutting back to 2x concentration. (I tried going to 4x in an effort to improve shelf life.) I am positive it's CD-4 -- or at least, it's marked as such on the jar and it's worked for me before. FWIW, I don't use the blix from that page, just the C-41 developer (and the RA-4 developer, but that's another matter).