Hello all, I'm having trouble finding the answer to this but I've been told it's possible to do like a reverse gravity reading with a refractometer and hydrometer. How can I find the original gravity from a final gravity reading? Thanks.
Getting an original gravity from a final gravity reading.
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petrolSpice
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If you have your recipe you can plug it into an online calculator and it will predict the OG for you. If it's extract it will be very close. If it's all-grain it might be a little off depending on what mash efficiency you achieved.
https://www.brewersfriend.com/homebrew/recipe/calculator/
https://www.brewersfriend.com/homebrew/recipe/calculator/
Gnomebrewer
Well-Known Member
In theory you can do this. In practice, refractometer calculators are only estimates with the error margin increased when you work in reverse. Thus, you can get an estimate of your OG and ABV, but they will have a fairly high error margin - it may be more accurate just plugging your ingredients in to a calculator.
What were you FG readings on the hydrometer and refractometer?
What were you FG readings on the hydrometer and refractometer?
They were 1.025 and 12.1 brix. Not quite done yet but this beer is somehow ok after mashing to high. Couldn't get the mash temp down very fast so the original brix said 22 post boil. It was only supposed to be about 1.070 as an IPA but came in at 1.088 if the refractometer is correct. I had an idea for what the pre boil gravity should have looked like and it seemed higher so I had the sense to add more hops to balance it. But it was my first time using the refractometer and wanted to double check my numbers. It's still goin strong though so I think it will end up around 1.018 and 8.5 or so abv
Gnomebrewer
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We can use your current numbers: hydro = 1.025 (6.1 brix); refract = 1.050 (12.1 brix).
I'm going to use this calculator
http://onebeer.net/refractometer.shtml - they'll all be slightly different.
Put in your final brix (12.1), have a guess at the original brix (I'll start guessing at 20 brix) and press "calculate".
We are looking for the Final Gravity estimate to equal your hydro measurement (1.025) by trial and error. In this case, it's a bit high (1.0266) so I'll try a slightly higher Original brix. By trial and error, original brix = 20.6, final brix = 20.6 gives an FG of 1.025. Thus, OG = 20.6 brix or 1.087, which roughly matches your original measurement.
I'm going to use this calculator
http://onebeer.net/refractometer.shtml - they'll all be slightly different.
Put in your final brix (12.1), have a guess at the original brix (I'll start guessing at 20 brix) and press "calculate".
We are looking for the Final Gravity estimate to equal your hydro measurement (1.025) by trial and error. In this case, it's a bit high (1.0266) so I'll try a slightly higher Original brix. By trial and error, original brix = 20.6, final brix = 20.6 gives an FG of 1.025. Thus, OG = 20.6 brix or 1.087, which roughly matches your original measurement.
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