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Volume lost during fermentation

I seem to be loosing more beer in the brewing process than I expected . I calculated the boil loss, the amount in the pump and cooling coil, and the cone of the fermenter. Does any one know how much could new lost during fermentation through the vent as sugars convert to CO2 and alcohol

I’ve seen several homebrewers estimate the loss in volume due to fermentation at about 0.5 gallons per batch. It is for this reason, as well as others including trub loss, etc., that many homebrewers will actually plan on starting with 5.5 gallons wort in order to end up with a standard “5-gallon batch”. For a larger size fermenter, you’d have to go even bigger, like for 10 gallons maybe brew 11 gallons wort, etc. The volume loss is more significant than people often account for.

I think the largest “loss” of volume would be due to temperature change. A warmer solution takes up more volume than an equal weight of cooler solution. Active fermentation raises the temperature, increasing the volume. When active fermentation ceases and the temperature drops as a result, it appears that volume has been lost.

wow, I never thought it was as much as 0.5 gallons. that is great info to know.
I never seem to be able to get more than 44-45 bottles and I always assumed I was not doing a good enough job topping off the fermentation bucket or carboy to 5 gallons.

Thanks for the great comments. here is the whole story. I started with two two hearted clone packages, added a litter of malt syrup to take care of the waste in the brew process. I was going to leave some in the boiler, some in the pump and tubes and cooler, some in the conical bottom, some for the drained off yeast. I estimated that I needed 13 gallons of liquid to start with to end up with ten gallons of beer. I got 7.5 pumped into the kegs.

I calculated a gallon of evaporation. Maybe that was 1.5., The yeast drain was 1/2 gallon, the waste in the bottom of the conical was 1/2 gallon, I ended with an OG of 11.5 going from a beginning of 13 gallons to end up with 7.5 still does not make sense. Converting sugar/syrup to CO2 and alcohol must make some difference in volume and of course cooing shrinks the volume.

How do I do the next batch to get 10 gallons of Two Heated?

PS: the last failed batch is like a good heavy beer with two shots of bourbon (maybe cheap bourbon)

What was the specific gravity at pre-boil, post-boil, and post-fermentation? Do you know the volume of the beer and crud you left in the fermenter?

I brew to hit a predetermined specific gravity, not to get a certain volume. Kits will give the advertised specific gravity at the advertised volume into the fermenter, then there are losses to trub, hops, and yeast. If you have measured all the losses you can use brewing software to help you calculate the amount of additional fermentables and water to add.

[quote=“Old_Dawg”]What was the specific gravity at pre-boil, post-boil, and post-fermentation? Do you know the volume of the beer and crud you left in the fermenter?

I brew to hit a predetermined specific gravity, not to get a certain volume. Kits will give the advertised specific gravity at the advertised volume into the fermenter, then there are losses to trub, hops, and yeast. If you have measured all the losses you can use brewing software to help you calculate the amount of additional fermentables and water to add.[/quote]

Let’s turn a negative into a positive. Lost volume is just nature’s way of forcing you to start your next batch sooner rather than later… :cheers:

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