Troubleshooting Homemade C41 chemistry.

Hello Photrio friends, dignitaries, and great minds!
This is my first post on your forums, though I have used the resources contained here for at least three years.
Though there is a lot of information on the topic already, I still find that I can’t seem to get a workable negative out of homemade chemistry.

The first three recipes I made all yielded the same result, so I’ll only share the last one.
I was using the flexclone recipe (minus calgon) from https://www.photrio.com/forum/threa...ow-does-it-compare-to-commercial-chems.74564/ and still getting nearly crystal-clear orange negatives.

I posess no means to test the pH, so I added 2 grams of baking soda to steer it alkaline, and after my first run, some faint and scannable negatives appeared. They were super thin, but complete. And the colors were more-or-less correct.

happy that i was on the right path, I doubled the baking soda to 4g.
No change. quadrupled, no change.

what gives?
I’m no chemist, so I have no idea what next to try. My scale is accurate, my water is distilled, and my temps are controlled.

I’m not asking anyone to walk through this with me, but if someone knows a few easy variables I can try tweaking it would be lovely to know where to start.

Thanks~
~John

Baking soda has a set "solution pH" and adding more will not make the solution any more alkaline -- though it will provide a reserve of alkalinity to buffer against the addition of acid. What you need to do instead is use the correct chemical. Every C-41 recipe I've seen, including the one you linked, calls for the carbonate -- in this case, actually potassium carbonate, though if you correct for the change in molecular weight, you'll be fine with sodium carbonate -- but you're using the bicarbonate, and sodium hydrogen carbonate. The formula actually uses both, which establishes a buffer system that will keep the pH nearly constant as you use it.

The big difference between the two, for our purposes, is that sodium carbonate has a significantly higher solution pH than sodium bicarbonate. The carbonate will make a pH as high as 11.6, while the bicarbonate will only to to a maximum of 9. Combining the two will give a value in between (as I recall, something around 10.6 for C-41 color developer), with the ability to robustly maintain it.

Use the correct mix of washing and baking soda (and correct appropriately for sodium vs. potassium salt, and for the water of crystallization -- washing soda is the monohydrate, while your formula may want anhydrous) and you should get correct results, assuming you used the correct chemicals otherwise.

It might help others who know more than I about C-41 chemistry if you'll post the exact formula you actually used (i.e. what you actually put in the mix, rather than just what the formula called for) and what process you went through to mix it. I've personally used Dignan's 2-bath C-41, home mixed from scratch, and had very good results -- but it uses only carbonate, no bicarb at all, and it has all of that in the second bath (the Bath A contains all the "good stuff"; Bath B is just the carbonate).

Target pH of c41 deceloper is usually 10.00 but home brew concoctions may require up to 10.25 for the required contrast in my experience. When homebrewing c41 developer, it is a very good idea to invest the $20 in a somewhat decent pH meter.

As indicated above, you need carbonate, not just bicarbonate. A moderate understanding of organic chemistry is beneficial to the outcome of such experiments. Learning about it can be fun, but if it's not your cup of tea, store bought chemistry is usually a better option.