Kirk, you were right! I re-ran the precipitation-experiment at 20C (instead of 30C), and sure enough, slight cloudiness became visible after 40 min instead of 20 min. That means at 24C, it'll be 30 minutes, so this rule applies to the concentrate:
Originally Posted by Kirk Keyes
"If using hard tap-water, develop promptly, making sure development is finished within 30 minutes after mixing."
But I'd like to do better than that, so I'll investigate chelating agents.
I also waited one hour and then developed a test-strip to see what harm this cloudiness does. I'll scan it in 1-2 days.
@Relayer: I haven't forgotten your request to test your modified formula. I'd like to in a few days as time permits.