As a continuation of my current experiments, I tried mixing up some “standard” Caffenol C-L with 40g/L Borax rather than the usual Washing Soda. I didn’t add any Sulfite or Bromine so there should have been nothing hindering development. A test strip failed to develop after 45 minutes. It did take on a gray color, roughly equivalent to a sunglass lens (dark but definitely transparent), yet nowhere near the density that fully exposed film usually attains.
As a control, I developed another test strip in Rodinal for about five minutes.
This doesn’t show up very well, but the Rodinal strip is on the left, Caffenol C-L with Borax center, and fixed film base on the right. If you squint a little (or zoom in) you can make out the lines beneath the Borax strip, but nothing through the Rodinal. In hand, the difference in density is quite obvious.
I believe this singles the Borax out as the problem since it was the only alteration to a mix that had been working well previously. I’m guessing that for some reason I’m not reaching the published pH of 9.2 and the developers aren’t being activated sufficiently – it’s just not alkaline enough. This is purely a guess on my part. I ordered a pH meter and I’ll continue tests when it gets here.
In the mean time I’m thinking about further trials with standard C-L with Sodium Sulfite added. Wikipedia lists the pH of a saturated Sodium Sulfite solution at “about 9” so it shouldn’t cause too much trouble, though it apparently slows development somewhat – 30min rather than 15min for the “normally” agitated mixes. I think I’ll need to run test strips with at least 1hr development times.
A Shot Of Caffenol 