That SERVICE port gets everyone at least once.

Does the grit depend on the finish too, like maybe water based needs a different stop than oil? Taking his idea further, I bet the shop's humidity plays into grain raise as much as the paper does. Seems like the old guy learned it the hard way and just never explained the why.

Read somewhere that bleach keeps working til the developer runs out, so the timer thing is kind of a myth anyway. Watched a video where a guy checked his swatches every few minutes and saw the same slow change you're talking about. Take it with a grain of salt but strand testing always beats the clock in my book.