General Category > Yeast and Fermentation

Double Boiling, Double Fermentation

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I have a home brewing buddy who did a double boil and a double fermentation and achieved (what he said) 11.4%ABV.  I was unfamiliar with this technique and was trying to figure out his math behind it to see if it made sense.

Here is what he said.  He had an OG of 1.083 and finished off at .0995.

That part makes sense, but the metjod to how he got to it is where I got lost.

He let it ferment then reboiled it with 3lbs of dark LME and 7 lbs of cane sugar.  He repitched it the same yeast.  IT was for a 10 gallon batch.

It was a Double IPA and had a lot of hop additions, but that is irrelevant to the information I am inquiring about.

I have struggled with achieving high ABV (above 9%) and is this metjod a common practice to achieve higher ABV?  Is there advantages / disadvantages to this method?  Does the math add up?

I guess that I would want to know how it tasted....I am no expert, but if my understanding is correct, the boil after fermentation would have driven off the alcohol content of the beer (think how distilling works).  Unless he captured (distilled) the alcohol and added it back, any contribution of alcohol from the original steps were lost.

He said it tasted smooth and cleared up nicely.  That is about all I got from him.

i haven't been homebrewing long, but i do know that alcohol boils at a much lower temp than water.  if your friend re-boiled his wort (beer, actually) he lost a ton of alcohol in the process.  i'm not sure what the LME and cane sugar would produce for alcohol, but you can't really take the previous alcohol content into account.  something smells fishy about the math.

If he truly boiled the finished beer a second time, then I've never heard of that technique. In addition to boiling off alcohol, I'd worry about off-flavors from yeast lysing.

Adding simple sugars near the end of fermentation is a common technique for fermenting a high-gravity beer. It lets the yeast do their thing without having to fight the osmotic pressure of a very high-gravity wort from the beginning.

What kind of "struggles" are you having? As long as you pitch a sufficient amount of yeast, fermenting a 9% beer should be relatively routine. It's when you get to about 14% or so that things get tricky.


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