Kodak 指示劑停影液（液體）黑白底片與相紙用（可調製8加侖）

I was tired of guessing when my stop bath was exhausted, but the liquid concentrate makes mixing a breeze and the color shift is so obvious there's no second-guessing. Eight gallons of working solution from one bottle is great value for a hobbyist like me.

The color change is the best part—it turns purple the second it's exhausted, so there's no guessing when to dump it. I mixed a full 8-gallon batch and it's held up through a long session of paper prints without any fuss.

I've been using this stop bath for a few weeks now and the liquid concentrate mixes up effortlessly compared to powder chemicals. The indicator's color shift from clear to yellow gives me confidence that my fixer is still active.