Can higher fermentation temperatures make higher abv

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biggben

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I recently had a batch of winter ale that has stopped fermenting now and its at 8.3% abv. The recipe however stated that this was a 7% abv recipe it said to ferment at 65 degrees but i couldnt keep it down so it was a 70-73 degrees. Would this explain my high abv?

this is the recipe

7 lbs Light Malt Extract

3 lbs Light Dry Malt Extract

1 lb British Crystal Malt 50-80 L

1/2 lb Belgian Caramunich Malt

1/2 lb Special B Malt

2 oz Centennial 25 HBUs(Boiling) 60 min

1 Brewers Licorice stick 10 min

1 oz Willamette(Flavor) 2 min

Wyeast American Ale Yeast

For Bottling:

1 1/4 cup Dry Malt Extract Or 3/4 cup Corn sugar
 

GilaMinumBeer

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Higher temps can increase the metabolic rate of yeast but can also result on higher order alcohols. The dreaded fusels.
 
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biggben

biggben

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what is a higher order alcohol and will it be all right
 

GilaMinumBeer

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what is a higher order alcohol and will it be all right
Fusel Oils. The headache makers. Oily, hot, slick feeling in the mouth.

"If" you have them go easy or you will pay. the production is dependent on the yeast but 70-73 isn't too extreme so long as that is the actual liquid temp.
 

pimento

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What were your starting and ending gravities and what size batch was it?

70-73 degrees isn't terribly high for an ale and fusels aren't likely to be produced in high enough amounts to alter your ABV.
 

jollytim

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Did you use 'top up' water? It's possible that your initial gravity reading may have been skewed if the wort wasn't mixed well. It does seem a tad high, but not unreasonable.

Unless it tastes 'hot', I wouldn't worry too much about it, but I understand trying to determine where and why things didn't go as predicted.

EDIT-

I did a quick and dirty plug in to an alcohol calculator (for extract): http://www.brewersfriend.com/extract-ogfg/
and it results in an approximate OG of 1.079 and FG of 1.018, with an ABV of 7.96%. That puts you right in the ballpark. Accounting for temperature when making readings may put you spot on.
 

DrJerryrigger

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High temps make fermentation times shorter and increase the potential for nasty alcohols, but it doesn't lead to higher % of ethanol, actually the opposite. When fermenting very strong wine with a yeast with a strong attenuation (appetite), say something like Lavin 1118, the yeast will go dormant due to high alcohol levels at higher temps, and at lower temps will keep on eating. So for a fast and full fermentation of said wine, the ideal temp would be quite warm to start, but then drop as the alcohol level increased.
This is not very useful info for beer brewing, as you are not maxing out the alcohol tolerance of your yeast, and not using a yeast with such a high attenuation.

As far as the nasty alcohols; I wouldn't think you would have much of a problem at those temps.
 
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