Refractometer for Final Gravity of fermented beer?

I recently bought a refractometer, calibrated it and calculated my brix correction factor. I am looking to eliminate the need for a hydrometer or at least minimize it. Can anybody tell me if I can use the refractometer to get an FG? I have read many different things and cant get a direct answer. FYI...I have beersmith and I see there is a way to possibly do this, but I can't figure it out. Thanks for any help

In short yes you can use a refractometer to get the FG of fermented beer. The alcohol will change the reading given off by the refractometer however there is an equation that only needs the original gravity. I use an iphone app called brew pal and just turn alcohol correction to "on". Also get used to taking your readings in Brix, even if your refractometer has SG readings because the calculatins use brix as input. I have used this on 2 batches so far and i feel like i can believe the numbers. happy brewing!

Alcohol throws off the reading, but there are formulas for correction. I actually have always used one; never started with a hydrometer. Listen to the 4/27/2011 Basic Brewing Radio podcast in which Sean Terrill returned from an earlier episode where he had solicited help from other brewers for regression data, and he revised the common formula. actually the earlier one probably does better explanation of why the difference on 9/2/2010. His site SeanTerrill.com has his results (I think in a usable spreadsheet form) and more info.

I use the calculator in Beer Alchemy now. I previously used BrewPal. They have different results, and no idea which is more accurate as you can't see the formula. But for my purposes of determining when fermentation is finished (no change in subsequent readings) and comparison from one of my own batches to another, it works fine.

It works- sort of.

It will not give you an accurate FG in my experience, even with correction tables and formulas. But it should be within .008 or so. That's a lot, so I don't trust it at all. It won't give you bottle bombs or anything- but the difference between 1.009 and 1.016 is pretty big.

There's also a spreadsheet available from a number of sources that will help with the conversion/adjustment once fermentation has started. Rebel Brewer has one (a web page actually), I think I've seen the same thing posted on other stores, but can't locate them right now. I also believe there's another one somewhere in the threads on HBT (haven't looked yet).

You'll want to use the brix reading on the spreadsheet. At first, I was annoyed by this since my first refractometer was SG and brix. But, I just recently picked up some more refractometers (two that go to either 32 brix, with a .2 resolution, and another to 20 brix with a .1 resolution) which makes it easier. I also have one that goes to either 60 or 62 brix (starts at 20 brix I believe), for testing other things.

I used the spreadsheet for recent batches and it converted to a good number. It was actually the estimated FG from BeerSmith.

I think they must have updated the formula used in the spreadsheet since the podcast mentioned earlier. I'll also be running the numbers through BeerSmith to see how that works out. I really like how little a sample you need for refractometer readings. Since I give my batches enough time to finish, I'm just looking to see what the FG is, so that I can get the ABV% number.

--update--
Refractobeer spreadsheet link...

Thanks for all the feedback. I think I figured it out on beersmith. It wants the final brix reading and the original SG reading and I guess it tells you the corrected FG and ABV. I may actually continue to use the hydrometer for FG's though, only because I enjoy drinking the sample and it seems i'll get a more accurate result. All my buddies always want to know..."whats the alcohol in this??"

Couple more questions: The brix correction factor, is that added or subtracted from the converted SG? I got a brix correction factor of 1.01544. does this sound right?

BigHead33 said:

Thanks for all the feedback. I think I figured it out on beersmith. It wants the final brix reading and the original SG reading and I guess it tells you the corrected FG and ABV. I may actually continue to use the hydrometer for FG's though, only because I enjoy drinking the sample and it seems i'll get a more accurate result. All my buddies always want to know..."whats the alcohol in this??"

Couple more questions: The brix correction factor, is that added or subtracted from the converted SG? I got a brix correction factor of 1.01544. does this sound right?

Click to expand...

Yes, that sounds about right. That is your correction factor for your hydrometer and refractometer. You plug your brix reading into the "refractometer tool" in BS and it will give you the corresponding SG number.

So I've seen these threads a few times recently, and they all seem to feature several folks saying "yeah, you can use a refractometer for FG, you just have to use this or that Excel spreadsheet," and Yooper saying "I've tried it and it don't work for s&%t."

I don't have a refractometer, so I have no direct experience. I'm sure I'll get one at some point, to (1) help track OG during brewday, and (2) at a minimum be able to track changes in FG.

But I'm wondering if anyone besides Yooper has found that there are major failures in the FG correction tools? At this point I'm really just curious, but I've noted several times people saying this works and then Yoop throwing cold water on it so I was wondering

Some may say I've always kept blinders on by never comparing side by side results. I haven't experienced any repeatability issues. So if in fact my refractometer measurements are off, I'm still consistent and routinely finish where recipe software predicts I should. So no reason for me to go get a hydrometer.

We could really have fun with the debate and suggest it has something to do with whether dry yeast or liquid was used.

I still use my hydrometer for final gravity readings, but next time I may have to give it a shot with the refractometer as well and see how they match up. Personally, I don't mind using the hydrometer, because its a lot harder to taste test my refractometer samples!

My refractometer was over +0.010 off of actual, even after using the several different 'corrections' available online for a few batches.

The funny thing is it was accurate on 2-3 other batches.

Can it be used? Yes. Is it reliable enough to justify shelving the hydrometer? No.

Eventually you'll experience what I did, and you'll have to use the hydrometer...

I have been wondering about the accuracy of FG readings as well. I have been using a refractometer for all of my readings and beer smith for my conversions and my ending gravitys seem a bit low. I made a lemongrass IPA with a OG of 1070 and according to Beersmith my ending gravity was 1008 which seems a bit too good if you ask me.

I just wanted to say, I ended up buying a hydrometer and did multiple readings. Turns out it the FG was 1.010. Thanks for the tip. Bad thing is, I broke the new hydrometer after I used it. Why I can't keep these damn things in one piece is beyond me.

I don't use my refractometer for FG readings any more, but when I did, I found that most tools and spreadsheets out there were way off. Sean Terril's spreadsheet got me the closest (within 3 points).

After reading this thread and doing my own observations, I'm wondering why I even bought a refractometer.

I just measured FG of a beer using both a hydrometer and refractometer before kegging, and here are the results:

Hydrometer OG: 1.060
Refractometer: 14.7

Hydrometer FG: 1.020
Est. ABV: 5.25%

Refractometer FG: 8.1
Estimated adjusted SG: 1.015
Est. ABV: 5.91%

A difference of 5 gravity points / 0.66%ABV seems like a lot to me. I checked these numbers against multiple online calculators and all yielded similar results. I guess I should stick with the hydrometer readings.

Oh well, it's a neat toy, but I'm not sure how useful it will be. I guess I can still use it to double check SG readings during mashes and post-boil, but it doesn't seem great for FG readings.

I was really hoping for it to replace my hydrometer, as I have a tendency to break them and they are less convenient, but that seems like a pipe dream now.

I was having some trouble with my refractometer but recently calibrated it and started getting much better results. I use it for og of course and to track fermentation. I always take a hydrometer sample for the fg but as far as I can remember the refractometer was pretty accurate on fg on the last few batches I have done. I just use the refractometer tool in brewzor (an android app) and like I said works pretty well. I probably wouldn't rely on the refractometer alone though.

A cheap refractometer will be more prone to accuracy issues. A quality unit will give much better results. Another case of getting what you paid for. For cheap, I'm talking about refractometers selling for <$50. Even comparing one of those to a quality unit, in hand, you can easily tell the build quality difference. The cheap one will be very light, while the quality unit will have some heft to it. Features like better calibration adjustments are also easy ways to tell them apart. I don't need any tools to adjust mine.

Use what you like, but [IMO/IME] those calling out that refractometers are not accurate are using cheap POS versions. Don't buy a Geo and expect BMW build quality.

If you are using Beer Smith or some other tool and use the correction tool you can compute what your correction is for your particular refractometer/hydrometer and the readings will be a lot more accurate. I am sure readings are probably slightly different between different hydrometers and different refractometers. Look at the standard hydrometer that comes in your basic brew kit and then look at one of the specialty say the FG one More Beer or AHS sells. The price goes up as precision goes up.