Diy ECN-2 chemistry resulted in dark negatives?

[koraks]

Washing soda can be anything from anhydrous to decahydrate.

Mix up a test batch of developer with the right amount of carbonate and see how that goes.

I don't know how that affects the developer

pH will end up way too high:

(quickly nicked from here)
Your developer should be at around 10.25 - 10.30 IIRC. Shifting the buffer to the right by adding an excess of carbonate will shift the pH point upwards. This will make the developer overactive and it will affect color balance as deeper layers (i.e. red, green) will develop faster in relation to the top layer (blue) than intended. It will also affect b+f, but the degree to which it happened here still makes me wonder whether this really explains what you're seeing. Still, it's definitely worth trying.

Also, if you can, test your developer with ECN2 film instead of C41, although the base of your C41 film processed properly in ECN2 should come out reasonably close in terms of density (not necessarily hue!) to the C41-processed sample you've got.

 

[filip0502]

Washing soda can be anything from anhydrous to decahydrate.

Mix up a test batch of developer with the right amount of carbonate and see how that goes.


pH will end up way too high:
View attachment 418087
(quickly nicked from here)
Your developer should be at around 10.25 - 10.30 IIRC. Shifting the buffer to the right by adding an excess of carbonate will shift the pH point upwards. This will make the developer overactive and it will affect color balance as deeper layers (i.e. red, green) will develop faster in relation to the top layer (blue) than intended. It will also affect b+f, but the degree to which it happened here still makes me wonder whether this really explains what you're seeing. Still, it's definitely worth trying.

Also, if you can, test your developer with ECN2 film instead of C41, although the base of your C41 film processed properly in ECN2 should come out reasonably close in terms of density (not necessarily hue!) to the C41-processed sample you've got.

Ok, I think I got 69 grams because I googled that the washing soda I was gonna use was decahydrate, and then 69 grams would be correct. I ended up getting something different, and it's anhydrous.
How can I test the pH? Is that something people regularly do when mixing ECN-2? I remember in school, during chemistry, we used some papers that changed color based on the pH level of a liquid.

 

[koraks]

How can I test the pH?

Strips or a pH meter. The latter are unreliable over the long term unless you get a really good one and maintain, calibrate & store it properly.
The papers you mention work, too, but are not very precise and really not exact enough for color photography unless you need to determine very gross deviations from target.

You can also just evaluate performance of the developer, but this requires everything more or less works OK. In your case, that's still an issue.