Gremlins have been drinking my brew

I've been brewing a mead with a SG of 1.107. I've noticed over the past couple of weeks the mead in the carboy has been going down little by little and not from me taking samples. my theory is that the yeast are eating the sugar like usual and converting part it to CO2 and less bulky alcohol and this is whats causing the drop in the level. anyone else notice this?

Methinks you have a sneak taking samples. I doubt that you would notice a drop in volume level by fermentation unless you were looking at krausen levels. The krausen will drop once fermentation subsides.

damn! some room mates/spouses have all the luck.

How much have you lost?

I noticed a drop in my gallon of JAOM, about two inches in the kneck which is about 1.5" wide.

Good question. In both cases, sugar + water and alcohol + water, the final volume is less than the sum of the component volumes. Since CO2 is being given off and ethanol is smaller than any of the sugars in honey, one would expect a reduction in volume. You would also expect a small amount of evaporation, despite the airlock.

But water is a very strange chemical, one of the very few that expands when freezing. And expands when heated.

More research is called for. Many, many test batches must be produced ... and consumed.

Deal!

I am going to start marking my carboys...

lol, do you have a kid? If so, there is your answer.

DEFINATELY no kids here, and it hasn't moved from it's original location.

WIP said:

DEFINATELY no kids here, and it hasn't moved from it's original location.

Click to expand...

You don't have to move a carboy if you have a long enough straw

Are you the only one with access to this carboy?

no its not krausen level drop. mead doesn't really have much karusen. I know for a fact no one but me has been messing with the carboy. i had slightly over 5 gallons of mead in a 5 gallon carboy. and yes that is possible, the 5 gallon mark is about half way up the slope to the neck of the carboy. its dropped maybe 1/4" vertical distance so not much has been lost. I'm thinking its only a few ounces at most.

Could the cooler temp have something to do with it?

I know when I clean a 5G carboy with warm water, after stiting overnight and cooling down the water will drop ~4 inches.

not impossible. but the temps have been more or less steady or warmer.

Quick google found this information.

Based on the coefficient of thermal expansion, β, ethyl alcohol has much greater thermal expansion than water. So as the ABV goes up, the effect of even small changes in T will express greater change in volume.

So, 5% beer = 5% alcohol + 95% water and other components.

Total β = 0.95*β(water@30*C) + 0.05*β(ethyl)= 287.85 + 56= 343.85 (this seems correct, but feel free to correct me on this.

ΔV = 343.85 x 10-6* 5gals* ΔT

Example: Drop in T of 3*C(also 3Kelvin) equates to a drop in volume of 5.16x10-3gals or 0.66 ounces. This doesn't take into account the changes due to undissolved solids, sugars, esters, yeast!, etc.

So it is possible that you are seeing volumetric changes due to temperature changes of just a few degrees. This calculation was for a 5% beer. Since your alcohol content is much higher in a mead, you will see greater changes.

Move it to a warmer area (few degrees) after marking your current level to see any changes.

That was a fun distraction! Thanks

http://physics.info/expansion/
ΔV = βV0ΔT

material volume β (10−6 K−1)
alcohol, ethyl 1120
gasoline 950
jet fuel, kerosene 990
mercury 181
water, liquid (1 &#8451 −50
water, liquid (4 &#8451 0
water, liquid (10 &#8451 88
water, liquid (20 &#8451 207
water, liquid (30 &#8451 303
water, liquid (40 &#8451 385
water, liquid (50 &#8451 457
water, liquid (60 &#8451 522
iwater, liquid (70 &#8451 582
water, liquid (80 &#8451 640
water, liquid (90 &#8451 695

very cool. that would imply that in the morning i should see one level and in the afternoon i would see a higher level because of a temp increase. but the thing is that the level never seems to go up and i'm seeing more than an ounce change in volume, a few ounces actually. if i understand the math i should expect up to 1.2 ounces change in volume.

there are 3 distinct karasin rings on the inside of the carboy. judging by the top ring and the current level i would estimate i've lost maybe half a cup.

i think the 3 leading causes for the drop are ethanol shrinkage, water/ethanol evaporation through the air lock, and yeast converting the sugars into smaller sugar molecules, ethanol, and CO2, which is escaping through the airlock.

also i've noticed a sticky residue on the outside of the carboy.

TipsyDragon said:

very cool. that would imply that in the morning i should see one level and in the afternoon i would see a higher level because of a temp increase. but the thing is that the level never seems to go up and i'm seeing more than an ounce change in volume, a few ounces actually. if i understand the math i should expect up to 1.2 ounces change in volume.

there are 3 distinct karasin rings on the inside of the carboy. judging by the top ring and the current level i would estimate i've lost maybe half a cup.

i think the 3 leading causes for the drop are ethanol shrinkage, water/ethanol evaporation through the air lock, and yeast converting the sugars into smaller sugar molecules, ethanol, and CO2, which is escaping through the airlock.

also i've noticed a sticky residue on the outside of the carboy.

Click to expand...

I would suspect the same. It would be a neat experiment for a future batch to measure the volume levels periodically and weigh the whole container at those levels. Then you can determine if the volume change is due to temps or evaporation.