I got spooky test-results! I mixed the formula again, but omitting the PG and decreasing the sodium metaborate by .1 g/L to maintain the same pH. Here are the curves with/without PG:
Originally Posted by Photo Engineer
They are eerily identical! At least you can't claim that my process lacks consistency. It makes one wonder if I actually added PG before. My log says so, and I remember measuring the PG. And if I didn't, the lower pH should have gotten my attention.
To summarize what I've seen: Adding 16 ml/L of propylene glycol (that's 1.6% of volume) causes dev-time to increase by 7% for test-strips. But it has no effect on complete rolls. I doubt this is a problem for typical users, but it's something that's haunting me.
PS: The title on the graph is wrong. I forgot to change that part of the gnuplot script-file.