I want to publicly express my appreciation to Alan for running these tests.
Originally Posted by Alan Johnson
BTW, in my prior posting of time-increases based on colour, I incorrectly assumed a linear drop in activity. As ascorbate is destroyed, activity drops slowly at first, and then faster. So I revised my estimates:
clear -------------> 0%
yellow -----------> 3%
dark yellow -----> 8%
orange ----------> 15%
dark orange ----> 30%
Alan is also concerned about water of crystallization (in the metaborate) hydrolysing the Phenidone. Coincidentally, I recently tried developer 214D modified by replacing the sodium metaborate with TEA. The interesting part was the amount of weight-loss due to evaporation during hot mixing: 214D loses about .30 g in the 1-liter formula. The TEA-version only lost .05 g, and my temperature was a little higher. That tells me that either (1) the metaborate-version loses much more water because more water is present, or (2) TEA prevents PG from evaporating.
If anyone cares to try it, I changed 214D to use 2.8 g of TEA-99% and 11 g of PG. The resulting concentrate is at the same 18 g/litre and yields the same pH of 8.08. But it develops faster. TEA seems to cause faster development than metaborate, even at the same pH. Anyway, 214D is similar to D316, and D316 survived a severe one-year test and did well in my extensive tests, so I'll stay with that formulation. TEA must wait.