Can the airlock give SO2 level info?

[Gekko4321]

I am bulk aging and about 1.5 months in. I added a 1/4 teaspoon of K meta when I started. I have Accuvin but honestly cannot determine info from that so went with blind 1/4 teas. The cap in the 3 piece airlock was always pushed to the top by the SO2 until recently. It started settling and is now back resting on the plastic piece within. When it was up, I knew it had adequate SO2, but now that it is down I am wondering. I intended to add another 1/4 teas of K meta at 3 months and then another at 6 when bottling. Do you think I am okay waiting or does the airlock give an indication to low SO2 levels? Thanks.

 

[robie]

The air lock doesn't give any indication at all of the level of free SO2 in the wine.

The internal, floating piece of the air lock moves up and down based on the amount of pressure inside the carboy compared to the amount of pressure outside the carboy. When there is a lot of CO2 still in the wine, it can bubble a lot, releasing that excess CO2.

Each time the air lock bubbles, the inside floating piece should move back down to rest on or near the base. As pressure inside increases, it moves up and off the base until it finally reaches the top, where it releases a bubble and repeats the cycle over again.

The fact that you seem to always see it at the top means only that the particular times you saw it, it was about to bubble or it had pretty much stopped bubbling and happen to be resting up near the top.

If you don't want to test for free SO2, add no more than 1/8th tsp every three months. I, as others on the forum, used to say 1/4th tsp, but I have found that with my own experience, that is too much. You didn't say if the wine is red or white, but for your particular wine, even 1/8th could be too much, but in most cases, it is a safe bet.

The only truly safe bet is to accurately test for free SO2.

 

[Gekko4321]

I stepped to the Accuvin testing based on advice on this forum but to me it is an arbitrary test. Measuring the result against a tiny colored faded box is next to impossible for me. I am sure with practice I may get good at it but it is pretty expensive test to practice on. I am not experiencing what you mention above with my red wine. I agree during secondary ferment I see airlock piece moving around but not during bulk aging. It is consistently at the top and has now gradually (2 weeks) declined to a resting position. In the past I have noted that when adding SO2 I would see it right to the top again. My concern obviously is this is an indication of weakening SO2 levels. I would hate to arrive at month 3 with an oxygenated batch. Seems impossible but a fear nonetheless.

 

[robie]

Hey, I understand; it pays to be careful, so no problem.
I know about the SO2 testing. It is not at all an easy test. That's why some of us just add the periodic Kmeta dose and hope for the best.

When you add more Kmeta, the air lock acts that way because either air got stirred into the wine, which alwyas will happen to some extent, or existing CO2 got stirred up enough that it is venting. Also, the addition of Kmeta can cause a little reaction when it hits any oak you may have in your wine and cause a little pressure.

Other than that, don't pay any attention to the air lock's floating piece's position.