I’ve used 510-Pyro often, and like the results, though I do believe it is staining some plastic parts in my developing tanks. I have a bottle that Jay DeFehr sold me what, five years ago? I think it’s probably weakening, though theoretically the TEA would inhibit oxidation, the way glycol does in HC-110. I note that the times on Mr. Hartung’s chart are for agitation every ten minutes, which in my lexicon would be semi-stand, so that may account for the extended times. FYI, if you don’t like the stain, Jay says that mixing some sodium sulphite into the water that you dilute the 510Pyro in will inhibit stain — I think it was 20g per liter, PM me if you want more precise info; I’ve got it in another computer.