View Full Version : Evaporation through airlock

12-22-2010, 06:50 PM
This is a weird question, does anyone else get significant evaporation through their airlocks? I've seen levels drop in my jugs and carboys by in some cases well over a cm (this is mostly only noticable when I have them topped off so they're part way up the narrow portion of the neck).

I thought one of the advantages of barrel aging was a slow evaporation that concentrated the flavours/aromas, but it seems to be occuring right through my airlocks...

Or is something else going on here?

12-22-2010, 07:38 PM

I have not noticed this, but I had a similar question/query.

If you if you think about mass balance, sugar eaten by yeast = alcohol and CO2, that CO2 goes out the airlock. Does this CO2 result in a noticeable volume loss?

However, this does not seem to be what happening in your batches, because your active fermentation is done...

12-22-2010, 07:40 PM
Is the level going down only during primary fermentation or the mead level continually go down during the entire time the mead is in a vessel with an airlock? If it is only during fermentation then my guess would be that the decrease in volume is proportional to the mass of the gas that escapes through the airlock.

If it is happening throughout the entire process then maybe the water in the mead is evaporating and going into gas phase. The vapor from the mead is coming into contact with the water in the airlock and the vapor is going back into liquid form at a greater rate than the water in the airlock is evaporating back into the mead.

12-22-2010, 08:05 PM
During fermentation the mass lost by CO2 is very measurable, some people here have even measured their SG by weighing the container as it ferments. Now, volume is a different issue - a dissolved substance may not increase the volume... I don't know if that applies to gasses or only to solids.

This is during aging. I did have a thought that it was maybe residual CO2 degassing, but I'm not sure if that effects the volume (I'm sure someone will clarify that though). It does seem to just be evaporating.