Refractometer: Correct Version...?

[KrafteD]

I bought a refractometer for brewing, one that was allegedly made for brewing and winemaking. But the scale inside the looking glass is different. It is shown in percentage scale (0-30%), not the decimal point system that’s on a hydrometer. Is this the correct one, or did I get one with the wrong scale? I need to return this in the next 24 hours because I’m going on vacation for 2 1/2 weeks and I’ll be passed my return window by the time I get back. Please advise.

 

[GaBrewZoo]

That is the right scale. It measures in Brix, which you can convert into gravity like what is on a hydrometer. Basically, 1 Brix is equal to 1.004 gravity. It's best to use a refractometer calculator. Pro brewers just talk in Brix, but I know I have to convert it to gravity to be able to know what I have, kind of like knowing a temperature in celcius, I won't know what it is until I convert it to Fahrenheit.
If your refractometer reads 15 Brix, your starting gravity is about 1.060. Figuring out your final gravity is a bit more complicated, but can be done with a refractometer.

 

[mongoose33]

What @GaBrewZoo said above.

If I were you, and could return it, I'd swap it for one that reads directly in specific gravity, not brix. It's not that you can't, it's that you'll have to constantly be making this conversion and that will get old very fast.

So--my advice is return it and get one with the gravity scale.

 

[dmtaylor]

I'd swap it for one that reads directly in specific gravity, not brix. It's not that you can't, it's that you'll have to constantly be making this conversion and that will get old very fast.

So--my advice is return it and get one with the gravity scale.

You have the correct refractometer. And I do NOT recommend trading in for one with an SG scale. The SG scales are notoriously wrong, not just for FG but for OG as well. You are always best off getting used to using a conversion calculator. This one is the best I have seen:

https://www.brewersfriend.com/refractometer-calculator/

 

[mongoose33]

You have the correct refractometer. And I do NOT recommend trading in for one with an SG scale. The SG scales are notoriously wrong, not just for FG but for OG as well. You are always best off getting used to using a conversion calculator. This one is the best I have seen:

https://www.brewersfriend.com/refractometer-calculator/

The world is full of masochists. But that makes things fun. Here's a scale like the one I have; can't imagine, in my wildest dreams, why I would want to constantly convert brix to sg, but to each his own. I suppose if you're professionally brewing, maybe, but then.....

 

[petemoss]

I have one as above with both Brix and SG scales. I personally only use the Brix scale. The reason for that is that you have to make conversions based on your reading anyway, especially for fermenting wort and FG. I use BeerSmith for this purpose. The calculator(s) in Beersmith use a Brix reading, therefore that is what I use. If they required an SG reading, then I would use that instead.

 

[dmtaylor]

Go ahead and use the SG scale if you want. As long as you understand that it's WRONG.

 

[mongoose33]

Go ahead and use the SG scale if you want. As long as you understand that it's WRONG.

OK, I'll bite. Might learn something. What is wrong about it?

 

[balrog]

I see for instance that the brix of 10.0 matches up with 1.044 so it has "helpfully" applied 1.004 "correction" factor to its Brix scale.

Question in my mind is, is that the correction factor?
I would only trust that as far as I trust any hydrometer to read 1.000 in distilled water, held at the calibration temp to which the hydrometer is manufactured.

In other words, I would test it at 1.000, and likely at other gravities.

 

[kh54s10]

I have read that some refractometer's sg scales are off. I checked mine when I got it and it is NOT wrong.

 

[Smellyglove]

OK, I'll bite. Might learn something. What is wrong about it?

There are lots of refractometers with both Brix and SG scales. I have seen a lot that has the wrong conversion. In the scale posted a few posts above, this is one of them. Look at 10 Brix, correct, then look at 16 Brix, wrong.

But there are also refractometers which are NOT wrong in the SG scale. I have one myself and I'm dreading the day I lose or break it because then I have to buy and return from different sources until I find one which is correct again.

 

[dmtaylor]

There is a wort correction factor (WCF) that is different for every individual gauge, such that a standard printed conversion scale is questionable at best. I have also heard that even the WCF is not a constant for different grists! Experimentation is required to learn the WCF for each gauge... Which then must be entered into a conversion calculator.

Refractometers also are not measuring SG at all but only refractive index, so don't let anyone be fooled into blind trust of an SG scale. Even calibration will not fix this fact, given the unknowns associated with WCF as discussed above.

Most importantly, if there is any alcohol present, a conversion calculator SHALL be used, lest the user will have complaints of "hey my attenuation always sucks" then receiving bogus advice to lower mash temp or pitch more yeast, when all that's really happening is that the alcohol increases the Brix reading.

Please, determine your WCF, only read in Brix, and always use a conversion calculator. IF you care at all about accuracy. And if not, then why ever measure at all??

 

[Smellyglove]

For what it's worth, I always measure OG with both a hydro and the refractometer, and they are in most cases on par with each other that I could just use the refractometer. (I didn't go for the cheapest hydrometer from ebay, but maybe one which was almost 2x the price of the cheapest ones) However, I've noticed that at higher gravity beers, with a lot of hop (oils) in them, the refractometer is not as correct anymore, due to what dmtaylor above said, the refractive index, My guess is that the oils are skewing it, since a high gravity with not as much hops is pretty correct.

 

[Robert65]

FWIW I don't really believe in the wort correction factor, not sure why some people seem to find evidence for its existence. I have two digital refractometers and a set of narrow range, professional brewery, Brix (Plato) saccharometers (hydrometers.) These are all alaways in complete agreement on wort, so I see no such factor. I suppose there may be something else going on with the handheld units.

I also am in agreement with Smellyglove that hop oils undoubtedly have a small but real effect on refractivity, but I just don't brew anything that hoppy so I'm not sure how big an impact this has.

In short, it's been a very long time since I've drawn the ~ 250 mL sample required for my saccharometers. I just use the refractometer and a nice little sample of about 2 metric drops. For beer with alcohol present, I use Petr Novotný's correction equation. The Brewer's Friend calculator incorporates this. I have also confirmed by saccharometer that this is probably the most accurate of the various formulas out there. (But remember, you may not need an exact FG reading anyway. If you get a consistent one over several days, you can safely assume that fermentation is complete. You can similarly track batch to batch consistency without being absolutely correct. And this doesn't just apply to refractometers, getting an accurate hydrometer reading isn't always easy either. Absolute accuracy is necessary for commercial brewers who have to pay excise based on alcohol content and remain within the specs on their TTB approved labels. We have different requirements.)

 

[dmtaylor]

FWIW, my WCF is 0.99. So @Robert65 's point about it being essentially meaningless, maybe he's right. But Terrill swears that the WCF averaged 1.04 for several other gauges, so who am I to argue as I myself only have one data point.

 

[mongoose33]

OK, i see--in the example I posted above, again posted below, the scale from brix to SG doesn't line up correctly.

Using this calculator https://www.brewersfriend.com/brix-converter/ if I put in

10 Brix I get 1.040 SG, on the scale from the refractometer, 1.044

15 Brix I get 1.0611 SG, on the scale from the refractometer, 1.066

So the problem is the scale isn't correct, one to the other. I'm presuming people have checked with hydrometers, but how do we know the Brix scale is correct and not the SG scale? Bears checking either way.

 

[balrog]

FWIW my hydrometers match refractometer at OG
I've yet to find anything on FG that is CONSISTENTLY correct between my hydrometers and refractometer.

During fermentation, my refractometer is "directional" only, letting me know as the fermentation levels off (I hesitate using the word "end").

{EDIT: @mongoose33 , to your point, my sciency background says you'd have to weigh out sugar and water, making solutions of known SG and measuring. But, no, I've not done that. That's my lazy-y background.}

 

[dmtaylor]

I'm presuming people have checked with hydrometers, but how do we know the Brix scale is correct and not the SG scale? Bears checking either way.

When you first get your refractometer, you'll need to check, double-check, triple-check, quadruple-check all your readings for a while with a calibrated hydrometer in concert with a conversion calculator every time until you are confident that it is reading consistently and accurately. Absolutely. You're right.

 

[dmtaylor]

FWIW my hydrometers match refractometer at OG
I've yet to find anything on FG that is CONSISTENTLY correct between my hydrometers and refractometer.

Petr Novotny formulae get me consistent accurate results for FG on a refractometer within an average 0.0015 gravity points compared to a calibrated hydrometer. It's possible. Not super easy but with enough attention to detail and a lot of calibrating, it is possible to get it that close consistently.

 

[deadwolfbones]

I've never bothered with the WCF because the differences, if they exist, are so small and ABV is functionally meaningless for a homebrewer. As long as I can tell when I've gotten to FG and know within ~0.5% ABV where it ends up, it's fine.

 

[balrog]

and another thing, the last refractometer I bought had a lovely picture showing the brix and sg scales, but the real life scale lined up differently.

I only ever read the brix side. Might as well be heiroglyphics on the right side for all i care

 

[kh54s10]

Please, determine your WCF, only read in Brix, and always use a conversion calculator. IF you care at all about accuracy. And if not, then why ever measure at all??

It is really about degrees of accuracy. If I use my SG scale which is pretty accurate, and I don't care if I calculate 6.2 or 6.5 as my final ABV, any use of correction calculations it for me a total waste of time.

 

[balrog]

Petr Novotny formulae get me consistent accurate results for FG on a refractometer within an average 0.0015 gravity points compared to a calibrated hydrometer. It's possible. Not super easy but with enough attention to detail and a lot of calibrating, it is possible to get it that close consistently.

I'm trying to be careful but I have to imagine I'm not careful enough:

 

[dmtaylor]

I've never bothered with the WCF because the differences, if they exist, are so small and ABV is functionally meaningless for a homebrewer. As long as I can tell when I've gotten to FG and know within ~0.5% ABV where it ends up, it's fine.

It is really about degrees of accuracy. If I use my SG scale which is pretty accurate, and I don't care if I calculate 6.2 or 6.5 as my final ABV, any use of correction calculations it for me a total waste of time.

You guys really are not wrong there either. I'm a little more nit-picky I guess. I want the "right" answers always.

 

[dmtaylor]

I'm trying to be careful but I have to imagine I'm not careful enough:
View attachment 639013

Those are outliers. You'll probably find though that on the average, the FG is pretty damn close to accurate.

 

[kh54s10]

You guys really are not wrong there either. I'm a little more nit-picky I guess. I want the "right" answers always.

What is "right"?

 

[dmtaylor]

What is "right"?

"Good enough". It's a personal decision.

 

[Carolina_Matt]

Interesting. I've always used the calculator when getting the FG, but I never used it on brew day. I assumed the SG was correct. I'll start using the calculator to see if that works better.

My main problem with a refractometer is that sometimes it's hard to see what the reading is. I have good vision, and sometimes it's still tough to tell whether it's (let's say) 6.2 Brix or 6.6 Brix. I can't imagine how hard it is for people with lesser vision.

 

[deadwolfbones]

Interesting. I've always used the calculator when getting the FG, but I never used it on brew day. I assumed the SG was correct. I'll start using the calculator to see if that works better.

My main problem with a refractometer is that sometimes it's hard to see what the reading is. I have good vision, and sometimes it's still tough to tell whether it's (let's say) 6.2 Brix or 6.6 Brix. I can't imagine how hard it is for people with lesser vision.

Adjust the diopter and tap on the plastic cover to produce a sharper line.

 

[kh54s10]

Interesting. I've always used the calculator when getting the FG, but I never used it on brew day. I assumed the SG was correct. I'll start using the calculator to see if that works better.

My main problem with a refractometer is that sometimes it's hard to see what the reading is. I have good vision, and sometimes it's still tough to tell whether it's (let's say) 6.2 Brix or 6.6 Brix. I can't imagine how hard it is for people with lesser vision.

Are you using the focus on the refractometer? It should not be hard to see. You can correct for your vision.

 

[balrog]

foreign material and bubbles will degrade the sharp line
brighter light is also much better to read it

And bonus points when wanting to use the outdoor sun to read refractometer, when you suddenly dart out of your garage into the bright sun super early on a Saturday, and scare the living daylights out of the Jehova's Witnesses coming to your door. Ah. Good times.

 

[Carolina_Matt]

To be clear, it's not necessarily that the line itself isn't sharp. I do adjust the focus on it so that it's clear. It's just that the window is pretty small. Maybe refractometers are different sizes and I just have a small one - I'm not sure - but I can't imagine someone with mediocre eyesight seeing the numbers inside the tiny looking glass on my refractometer.

 

[dmtaylor]

It ain't easy taking a reading. Measure twice, cut once... or something like that.

 

[Smellyglove]

To be clear, it's not necessarily that the line itself isn't sharp. I do adjust the focus on it so that it's clear. It's just that the window is pretty small. Maybe refractometers are different sizes and I just have a small one - I'm not sure - but I can't imagine someone with mediocre eyesight seeing the numbers inside the tiny looking glass on my refractometer.

I feel the same way sometimes, It's sharp, but I feel that I reeeally have to try to zoom in with my eyeball, which is a kind of quite hard to do. But also, If you try to read it several times it becomes easier, I don't know if it's the eye which need to refocus or what and just get used to the small numbers and lines.

 

[Robert65]

I like the digital refractometer. For many reasons, not the least of which is that it never has any trouble reading itself. I know the price is off putting to many, but I've spent my money worse in this hobby.

 

[balrog]

and don't even start me down the rabbit hole of trying to cobble something together to photograph the refractometer "because it should be easy and remove the issues with astigmatism I have and shaking hands when it's 15°F and and"

It's not easy. I'm about ready to go the @Robert65 , digital refractometer path.