Refractometer advice or suggestion

ChrisR · November 8, 2019, 2:11am

Hey all. So I screwed up a mash because I didn’t get the grain milled enough. My OG was 1.032. So I threw a Hail Mary and added some sugar solution to the primary. 1.25 pounds dissolved in about a quart of water. I didn’t take a revised OG reading because I did it about 24 hours in when fermentation was already rolling.

No doubt I broke some rules and maybe that’s for another discussion… My question is whether I can use a refractometer to get a decent abv measurement. I was considering buying a cheap one. I did tweak my beer smith profile to match my actual OG and it said the sugar would add 1.5% on a 5 gallon batch. That seems too good to be true.

Rambling aside, I’d like to insight on using a refractometer to measure ending abv. Or I could sit down and see how many pints it takes to do the trick!!

Grantmesteven · November 8, 2019, 3:10am

I would get a hydrometer for measuring final gravity. It will probably be difficult to figure out what abv you actually will end with

sneezles61 · November 8, 2019, 11:22am

As Grant sez… I have a " finishing " hydrometer… It reads from 1.020 down to 0.90… Scale is stretched out a bit so my eyes don’t have to squint (like Clint)… Sneezles61

Rburrelli · November 8, 2019, 1:38pm

A refractometer does not measure gravity accurately in the presence of alcohol. That it why we all own hydrometer for final gravity measurement. You can do it with a refractometer but it involves some calculations and knowing what your original gravity was, which you do know. Take some time to read about it.

Also, there is software that will tell you how much sugar (or other fermentable) you need to add to your post boil gravity to offset your shortage, rather than just using a random amount.

Steve · November 8, 2019, 6:46pm

Our host’s refractometer calculator is here.
If you know your original gravity, or brix, you can approximate abv using it. With no alcohol in the mix, the conversion between gravity and brix is straight-forward. As Rburrelli said, in the presence of alcohol, you have to use the calculator.
As also noted above, a hydrometer works well.
There is another abv and calorie calculator here
.

squeegeethree · November 9, 2019, 9:59am

what @Rburrelli said x2

dmtaylo2 · November 9, 2019, 2:23pm

@Steve was on the right track. If you have both final Brix from a refractometer and final gravity from a hydrometer, you can use these two values to back-calculate the OG and ABV. See the following link for the equation I use which I have found to be quite accurate within about 0.4% ABV or 0.004 of the true OG.