Andrew, I feel your pain !! About 2 years ago I had a similar problem, after years of nailing the results. I could not get any consistency, the numbers were all over the place, so I first replaced all the chemicals, then bought a new vac that I could control better, and continued to beat my head against the lab walls. I spoke with ETS, brought in my quality assurance guy and no matter what we did, we could not solve the problem. Looking back, I don’t even want to guess at the amount of hours spent trying to figure this out. So I solved it alright, set the pretty glass decoration aside and bought the HI 84100 and have not had one problem since. For us, it just wasn’t worth our time to continue to fight something that we had no confidence in. The hannah is easy to use, and well worth the money spent.
Good luck !
Linda
Thanks, Steve G., for your suggestion.
The Vinmetrica is working well for us.
I posted in more detail here: Hanna Instruments HI 84100-01 Mini Titration System for So2 Measurements - Cellar Rats (ITB) - WineBerserkers
I’m glad to hear the Vinmetrica unit is working out for you, Andrew. Its so much quicker and easier that I find myself testing when it needs to be done, rather than thinking I’ll do it next time I have the bung out. Now I just want them to develop a similarly easy tool for verification that MLF is done.
Thanks again for suggesting the device. As you say, SO2’s are now much more likely to get done on time rather than put off.
Do you have a hard time with your paper chromatography?
That seems easy enough to me. We normally do it twice a year. Once to see how far along everything is and once to be sure they are all done.
The problem with paper chromatography is it can’t/doesn’t show anything below 100mg/L…but 30mg/L is considered complete (and ideally below 10mg/L). So PC isn’t enough if you want to be sure.
I don’t doubt that what you say is technically correct. OTOH, we have been doing it this way for 26 years and never had a case of ML in a bottle. We wait until it is done on the paper plus a set period of time for extra measure. Then again, a lot of what we do is pretty low tech.
Some people also sterile filter all white wines since they consider malic unstable. Again, never had one go in a bottle.