I use Salifert kits for all my tests. I now read an article by ol' Randy which talks about "fugitive endpoints" when doing titration-type tests (the kind where you add drops until the colour change, and then read the result off a chart). Specifically, he advises that you should stop adding drops the moment you observe a colour change. Even if the colour reverts back the way it was. The bloody salifert kits' english Instructions don't mention this!!! Die Hollandaise instrukties ist meer duidelijk in sovaar hierdie geval. Or some . No parle voux Francais pour merde, either! BUT. Even though I know this now, this still doesn't solve the problem. The magnesium kit, I think it is, will impart a blue colour to the newly added drop immediately, which then disappears. At some point as you add drops, the solution turns blue and then pink again. And eventually it remains blue. So now wobble you tea eff?!? Which one? Grrrrrr.