How Do You Know How Much ABV Is In Beer, After It's Bottled??

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Permalink Reply by Peter Church on October 14, 2015 at 8:02pm

You can measure the finished gravity, sample in a trial jar, le

ave to go flat then used hydrometer. Then its a guess where it started, if you kept records then you could estimate a range of starting gravities based on grain bill, water vol and an assumed efficiency. Or geta lab analysis done, not really worth it

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Permalink Reply by Darren Andrews (Daza) on October 14, 2015 at 9:45pm

Hey true just go back to the recipe it says OG was 1.052 not that my reading was accurate but that will be a good place to start, now the hard part letting my go flat on purpose!

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Permalink Reply by Peter Church on October 15, 2015 at 10:39am

my understanding is that you added 5 litres to that so the OG would come down to ~1042 

the recipe would be based on an assumed efficiency which would not normally be hit on your first brew, so conceivably your original gravity could be down at 1035-8ish so its probably mid to high 3's based on a heap of assumption and guess work

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Permalink Reply by mattd2 on October 15, 2015 at 12:29pm

I'm thinking this depends on why he only got 18L - if he boiled off more than expected then the 18L would be expected to have a higher OG and watering it down would bring it back to the 1.052 mark (less any efficiency issues he may have due to being the first beer). If it was he left a whole lot of wort throughout the process then what you said would be correct.

Darren - any idea what your volume was pre-boil?

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Permalink Reply by Peter Church on October 15, 2015 at 1:29pm

hi matt, true, i assumed the og was for the 18 l but that could be completed wrong, well done on finding time to make beers for competitions too, good luck with that

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Permalink Reply by Darren Andrews (Daza) on October 15, 2015 at 4:34pm

yep it was 30L pre-boil. 20L post boil (75min) I guess other 2 was from cooling and transfer.  I like where your head is at, like a detective working on the case of the missing ABV!!!

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Permalink Reply by Nathan on October 14, 2015 at 9:46pm

Or like said above take a reading post your grain bill and we could come to some assumptions based on efficiency to get a ball park SG

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Permalink Reply by Darren Andrews (Daza) on October 14, 2015 at 10:01pm

I'll do it tomorrow, only need a 100ml in trial jar. Let you know the reading then. Cheers

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Permalink Reply by Darren Andrews (Daza) on October 15, 2015 at 12:01pm

Ok cool Peter not what I was aiming for but I'll take it....I made alcohol!!! Yay.

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Permalink Reply by Darren Andrews (Daza) on October 15, 2015 at 2:34pm

I did do a real vigorous boil for 75 min losing 10L from 30L giving me 20L before cooking and transferring to fermenter giving me 18L

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Permalink Reply by Darren Andrews (Daza) on October 15, 2015 at 2:37pm

Cooling not cooking

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Permalink Reply by mattd2 on October 14, 2015 at 11:27pm

If you buy/borrow a refractometer you can calculate the abv from a hydrometer reading and a refractometer reading.

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