Refractometer

[dmtaylor]

I did this correction factor calibration a few years ago when I first bought a refractometer (see below). I was a bit surprised when the result came out below 1.0 because everything that I had read suggested that it would most likely be ~1.04. So, I decided to continue monitoring it with almost every brew I have made since then. The average so far is 1.025, but the individual results are all over the place
I have no idea whether this is because my refractometer is rubbish, or if it is due to measurement error? So, for the now I do not rely on it for my ABV calculations, and continue to use a hydrometer. It's a shame because the refractometer is so quick and convenient to use.
I didn't pay a lot for the refractometer (I can't remember how much, but I think that it was ~£25.00), so perhaps a better quality one would be more reliable?????

You can use your cheap refractometer with good repeatability. I use a cheap one. You just need to pay close attention to pre-calibration and post calibration. With every single wort reading you take, measure plain water both before and after your wort measurement. Use the average deviation from zero from the water measurements to determine the true reading. My standard guidance for calibration is linked below.

By the way… my correction factor is definitely 0.99… so I think values less than 1 or 1.04 are possible, and probably common. The 1.04 is just an average of a few guys from Colorado or whatever. And who knows how well they calibrated their refractometers. Probably not like I do.

https://www.homebrewersassociation.org/forum/index.php?topic=28544.15

 

[Hop_it]

You can use your cheap refractometer with good repeatability. I use a cheap one. You just need to pay close attention to pre-calibration and post calibration. With every single wort reading you take, measure plain water both before and after your wort measurement. Use the average deviation from zero from the water measurements to determine the true reading. My standard guidance for calibration is linked below.

By the way… my correction factor is definitely 0.99… so I think values less than 1 or 1.04 are possible, and probably common. The 1.04 is just an average of a few guys from Colorado or whatever. And who knows how well they calibrated their refractometers. Probably not like I do.

https://www.homebrewersassociation.org/forum/index.php?topic=28544.15

Thanks very much for that little gem. I really didn't think that the results could wander so much. I will certainly give it a try on my next brew.

As you are obviously a fan of refractometers, can you give me a bit of advice on taking the readings please? . . . . . Quite often when I take a reading with wort the dividing line between the blue and the white is not very well defined, and is quite fuzzy, but a reading with pure water gives a sharp dividing line. Is there a reason for this, and what is the best point to take the reading?

 

[dmtaylor]

Thanks very much for that little gem. I really didn't think that the results could wander so much. I will certainly give it a try on my next brew.

As you are obviously a fan of refractometers, can you give me a bit of advice on taking the readings please? . . . . . Quite often when I take a reading with wort the dividing line between the blue and the white is not very well defined, and is quite fuzzy, but a reading with pure water gives a sharp dividing line. Is there a reason for this, and what is the best point to take the reading?

Haze in the beer will fuzz the line. Try to get as clear a sample as you can, without disturbing any sediment. Otherwise all you can do is try to figure out the middle of the fuzz, that's your reading. You will indeed lose a bit of accuracy when the reading is fuzzy, but you should still be able to get a reasonable guess in the center.

 

[Hop_it]

Haze in the beer will fuzz the line. Try to get as clear a sample as you can, without disturbing any sediment. Otherwise all you can do is try to figure out the middle of the fuzz, that's your reading. You will indeed lose a bit of accuracy when the reading is fuzzy, but you should still be able to get a reasonable guess in the center.

Yes, that makes god sense . . . . Thank you very much

 

[The-Engineer-That-Brews]

Thanks very much for that little gem. I really didn't think that the results could wander so much. I will certainly give it a try on my next brew.

As you are obviously a fan of refractometers, can you give me a bit of advice on taking the readings please? . . . . . Quite often when I take a reading with wort the dividing line between the blue and the white is not very well defined, and is quite fuzzy, but a reading with pure water gives a sharp dividing line. Is there a reason for this, and what is the best point to take the reading?

Also make sure that you're putting enough liquid on to coat the glass fully and evenly, and especially that there are no bubbles when you close the cover

 

[Hop_it]

Also make sure that you're putting enough liquid on to coat the glass fully and evenly, and especially that there are no bubbles when you close the cover

Thanks . . . . that's a good point too

 

[PhilBrew]

I did this correction factor calibration a few years ago when I first bought a refractometer ... I decided to continue monitoring it with almost every brew I have made since then. The average so far is 1.025, but the individual results are all over the place

... but isn't that (almost) inevitable? The whole reason we need a "wort correction factor" is because our refractometers have been calibrated to measure Brix of a simple sugar (probably glucose) solution ... and, by using that wort correction factor calculator, we're calculating a correction factor to correct the readings taken with those refractometers; because a "typical" wort is instead made up of a range of different sugars (going from simplest to less simple ... glucose, fructose, sucrose, maltose, maltotriose, maltotetrose, maltodextrins, etc.) ... but we're brewers, we know that there's no such thing as a "typical" wort, we know we can alter the mix of sugars produced by varying the temperature of the mash (shifting the blend of sugars produced leftwards, towards the simpler end of sugars by mashing cooler, rightwards by mashing warmer) and/or by adding cara/crystal and roasted grains which will have higher proportions of complex, caramelised sugars and/or the products of Maillard reactions, or even as simple sugars added into the boil, or FV ... so we should recognise that the best we can (possibly) do is calculate a wort correction factor for the "typical" worts, we typically produce, which is all the wort correction factor is trying to provide

Given all of that, if you're like many (most?) homebrewers and produce a wide variety of worts to produce beers to different styles, you actually couldn't possibly ever calculate a wort correction factor for a "typical" wort because you don't produce any "typical" worts ... in which case, either you'll decide to give up re-calculating wort correction factor and stop chasing accuracy with a refractometer, plenty of people use only refractometers (pre and post-boil) after all ... or, like TETB above (and me, as it happens), recognise a refractometer as just a "handy tool" to give you an "indication" and then use another tool for your "real" measurements

Cheers, PhilB

 

[dmtaylor]

Calibrated properly, and using the brewers friend conversion calculator (Novotny correlation), I have found my refractometer FG results to be consistent and accurate for various beers as compared with a hydrometer within 0.002 gravity units. YMMV

 

[Sym]

I love my refractometer, it was under 20 quid on amazon, and it measures exactly the same as the hydrometer for OG every time.

Bit of a confession here - When i first got it i did not know about the FG altering the reading, and my brew came down to 6 degrees (1.024) but no further so I thought i had a stuck fermentation. I stirred it up, added turbo yeast etc then discovered the online calculators where you add the OG and FG readings and it gievs you the real FG reading, and discovered I was fermented down to target. oops. :) Anyway I have never calibrated mine, and it works brilliantly for taking samples during mash, boil, cool. I used to use it towards the end of the fermentation to see if it had completed, as it is much easier than taking a big sample for the hydrometer, but I now have an ispindel so don't need it so much for that now.

 

[peebee]

... calibrated to measure Brix of a simple sugar (probably glucose) solution ...

It's sucrose: Brix - Wikipedia. I like that link because it expresses SG with both calibration points (20°/20 °C), something I'm always banging on about ... proof I'm not making things up (again)!

... "typical" wort is instead made up of a range of different sugars (going from simplest to less simple ... glucose, fructose, sucrose, maltose, maltotriose, maltotetrose, maltodextrins, etc.) ...

And of course, the mix of sugars changes as fermentation progresses (yeast munches the simplest sugars first, some never get past maltotriose). How much difference might that make? (Who cares, but some will).

I have found my refractometer FG results to be consistent and accurate for various beers as compared with a hydrometer within 0.002 gravity units.

To some, that degree of accuracy will have them running about like headless chickens. For example, here's screen shot of output from new Tilt PRO (count the decimal places!):

 

[Hop_it]

... but isn't that (almost) inevitable? The whole reason we need a "wort correction factor" is because our refractometers have been calibrated to measure Brix of a simple sugar (probably glucose) solution ... and, by using that wort correction factor calculator, we're calculating a correction factor to correct the readings taken with those refractometers; because a "typical" wort is instead made up of a range of different sugars (going from simplest to less simple ... glucose, fructose, sucrose, maltose, maltotriose, maltotetrose, maltodextrins, etc.) ... but we're brewers, we know that there's no such thing as a "typical" wort, we know we can alter the mix of sugars produced by varying the temperature of the mash (shifting the blend of sugars produced leftwards, towards the simpler end of sugars by mashing cooler, rightwards by mashing warmer) and/or by adding cara/crystal and roasted grains which will have higher proportions of complex, caramelised sugars and/or the products of Maillard reactions, or even as simple sugars added into the boil, or FV ... so we should recognise that the best we can (possibly) do is calculate a wort correction factor for the "typical" worts, we typically produce, which is all the wort correction factor is trying to provide

Given all of that, if you're like many (most?) homebrewers and produce a wide variety of worts to produce beers to different styles, you actually couldn't possibly ever calculate a wort correction factor for a "typical" wort because you don't produce any "typical" worts ... in which case, either you'll decide to give up re-calculating wort correction factor and stop chasing accuracy with a refractometer, plenty of people use only refractometers (pre and post-boil) after all ... or, like TETB above (and me, as it happens), recognise a refractometer as just a "handy tool" to give you an "indication" and then use another tool for your "real" measurements

Cheers, PhilB

I am one of those brewers who tends to make something different every time, so I accept that there is no such thing as a "typical wort" in this scenario. I also accept that there are many factors that can and will affect the calculation of a viable wort correction factor. However, the purpose of my original post was only to act as a polite warning to LisaMC (based on my own limited knowledge and experience) that she might not find it easy to derive a consistent figure for the wort correction factor.
Having now learnt more, I accept that there are many potential sources of error, and I am also prepared to accept that there are better tools available to obtain more precise measurements. But even if you only want to use a refractometer as a "handy tool" during a brew day, you still need a figure for a correction factor . . . . . despite the fact that it may not be absolutely true and precise. Hence the reason that I continue to make comparisons with my hydrometer readings in the hope that I will (slowly) get closer to a "best fit" figure - or maybe not

 

[PhilBrew]

Hi @Hop_it

However, the purpose of my original post was only to act as a polite warning to LisaMC (based on my own limited knowledge and experience) that she might not find it easy to derive a consistent figure for the wort correction factor.

... and the purpose of my post was simply to explain how (and why) consistency for wort correction factor is almost impossible (it is only likely to be possible if you were working in a brewery producing the same wort/beer over and over again, as in a commercial brewery) ... which is why the calculators for wort correction factor take an averaging approach and why, at some point you're likely to have to accept that that average "is good enough" ... as will LisaMC

I'm not trying to convince you to not use a refractometer ... whether you do or not is up to you and only you can decide whether it suits your needs and fits in with your brewing practices ... I'm just trying to explain the pros and cons that they have ... and the same for LisaMC

Similarly, only you can decide how accurate you feel you need to measure gravities and strengths of your worts and beers, it's only homebrew after all ... and only you can decide how much money and effort you're willing to invest in gaining those levels of accuracy ... and LisMC will need to make her decisions for herself ... all we can do on this forum is give information which might help you make those decisions which, to be clear, is what I was trying to do

Cheers, PhilB

 

[Hop_it]

Hi @Hop_it
... and the purpose of my post was simply to explain how (and why) consistency for wort correction factor is almost impossible (it is only likely to be possible if you were working in a brewery producing the same wort/beer over and over again, as in a commercial brewery) ... which is why the calculators for wort correction factor take an averaging approach and why, at some point you're likely to have to accept that that average "is good enough" ... as will LisaMC

I'm not trying to convince you to not use a refractometer ... whether you do or not is up to you and only you can decide whether it suits your needs and fits in with your brewing practices ... I'm just trying to explain the pros and cons that they have ... and the same for LisaMC

Similarly, only you can decide how accurate you feel you need to measure gravities and strengths of your worts and beers, it's only homebrew after all ... and only you can decide how much money and effort you're willing to invest in gaining those levels of accuracy ... and LisMC will need to make her decisions for herself ... all we can do on this forum is give information which might help you make those decisions which, to be clear, is what I was trying to do

Cheers, PhilB

Yes, agreed. . . . . The better we know and understand the vagaries, limitations and pitfalls of any piece of equipment or brewing technique, the better able we are to make informed decisions. I have already learnt quite a lot from this thread, for which I am very grateful

 

[peebee]

... to explain how (and why) consistency for wort correction factor is almost impossible ...

Did you read further into that "Brix" link I posted? Fascinating stuff! We'll all want Infrared Absorption devices soon. Hydrometers, refractometers, pyknometers ... pah, old hat: I'm waiting for the "Tilt IR" which will be telling me how much maltotriose, etc. I've got left.