Quote Originally Posted by Photo Engineer View Post
You know that if you don't test that new alternative, it will haunt you!
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:


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.

Mark Overton

PS: The title on the graph is wrong. I forgot to change that part of the gnuplot script-file.