Refractometers - only final runnings?

[user 246304]

Never used one, always used hydrometers, but thinking of including one in my brewing larder for brew day measurements. However, in all reality, I'm not sure I want to rely on it for anything but knowing when to cut runoff. Besides wasting wort, waiting for the sample to cool to allow a decent hydro reading, well, you know.

However, an instrument costing $90 and up, for one dedicated purpose - and at that, a ballpark - seems a bit pricey to me.

Others? AJ, hoping you chime in here...!

 

[doug293cz]

There are a lot of refractometers available for less than $90. No matter how much you spend on one, you need to correlate the results with a hydrometer, in order to determine the "wort correction factor." Refracts are calibrated to sucrose solutions, and wort is much more complex, with sucrose being a minor component. Most refractometer calculators allow for the input of the wort correction factor for your refractometer, so that you get accurate conversion of Brix to SG. Never trust the "SG" scale on a refractometer, unless you have verified it.

Brew on

 

[schematix]

good tool to have, but as already has been mentioned, they don't measure the same thing a hydrometer does.

the wort correction factor varies from beer to beer too. i regularly see swings as much as 10% between refract and hydrometer for different worts.

I would say they are a fantastic tool when applied in the right conditions. You can get one for about $30 though.

 

[user 246304]

Both, correct me if I'm wrong, are based on sucrose in solution. It just happens that density isn't as touchy as refraction due to the company of sugars (and not pure sucrose) in typical wort.

I guess what I'm trying to say is that the real benefit I see, anyway, is to be able to get an approximation on the fly - but because of a refract's comparatively greater range of potential swings in readings, I wouldn't want to really use it anywhere but cutoff. I prefer a good hydro for everything else.

But, thanks for thoughts guys, it's what I was asking - do you find them useful enough, basically, to warrant getting one.

Thanks, too, for saying the $30 ones aren't all junk. I'd thought just because I see Northern and others sell ones at $90-ish, and I know that they, like all lab-ish instruments can really run up there, that $90 was a baseline for anything of quality. Can I ask - do you happen to have any specific models you could recommend?

 

[dmtaylor]

$90?! You can do better than that. Here's the one I have, only $22, and it works just great.

https://www.amazon.com/dp/B01N7DIF0H/?tag=skimlinks_replacement-20

I've used it successfully on at least a dozen batches, probably more. It's consistent and reliable and I would buy it again if it does break, which it hasn't, despite being dropped a couple of times already.

 

[eric19312]

Ive got a couple of the cheap ones. I use extensively on brew day. First thing to check is gravity of primary runnings to see if conversion is complete. Last brew day I did 75 min mash, was sure I was complete, checked gravity against Kai’s table and saw was only about 92% converted. Got in there and gave it a stir and released and saw my clear wort go milky. 15 min later sure enough I was at 100% conversion and started my lauter.

Then I used it to check final runnings. Then pre boil gravity.

Only thing my hydro gets used for is OG and FG. I dont mess with wort correction factor...as someone above mentioned this can change beer to beer...but I’m never surprised by more than about 2 gravity points on my hydrometer OG vs refractometer pre boil gravity and expected OG based on evaporation.

 

[dmtaylor]

I dont mess with wort correction factor...as someone above mentioned this can change beer to beer...but I’m never surprised by more than about 2 gravity points on my hydrometer OG vs refractometer pre boil gravity and expected OG based on evaporation.

FWIW, I have honed in the wort correction factor for my refractometer, and it is precisely.... 0.99. It is NOT 1.04 as Sean Terrill reports as the average, so it is clear to me that it can vary pretty widely from instrument to instrument, but for mine... yeah.... it's so close to 1.00, and in fact slightly below 1.00 instead of above.

That said, the hydro vs. refract comparison in the FG can vary by as much as 4-5 gravity points (0.004-0.005) in my experience, especially for very high gravity worts, like my last batch with an OG above 1.090 and ABV of about 10%. It's not as accurate in high strength beers, so for those it's best to use a hydro. But below about 1.070, use Terrill's calculator and it will turn out pretty close, within a couple points like he says above.

The calculator is REQUIRED if you are using this for FG. You cannot interpret the results properly without pumping the Brix into these equations.

http://seanterrill.com/2012/01/06/refractometer-calculator/

 

[balrog]

I agree with @dmtaylor on correction factor, but I have worse match even with calcs on FG -- typically off 4-5 points, and most of what I make are 1.050 OG, 1.010-1.015 FG beers.

One thing I'd love to know is how to create a solution that would allow the calculation of what the hydrometer should read and what the refractometer should read. It is fairly simple for OG; add °P amount of sucrose to water. But what about creating a known solution of sugar and alcohol with say 80 proof vodka, sucrose, and water, so that you know the hydrometer should read 1.020 (calc the density) and the ABV is 5% (from the vodka) and then what the refractometer should read. Is that possible?

 

[dmtaylor]

But what about creating a known solution of sugar and alcohol with say 80 proof vodka, sucrose, and water, so that you know the hydrometer should read 1.020 (calc the density) and the ABV is 5% (from the vodka) and then what the refractometer should read. Is that possible?

Where there's a will, there's a way..... but that's a whole lot of mathematics. I could run the calcs, but.... nah. Feel free, if you are interested.

Actually.... maltose or malt extract will theoretically give you slightly different results from sucrose, so you should at least use malt extract, not sucrose, for greater accuracy and determination of your correction factor (which could be <1.000 or >1.000, depending, as I stated previously).

EDIT: And also, well, a finished fermentation should really not have any maltose or sucrose left in it, either. It's more of the unfermentable sugars such as maltotriose, dextrins, etc. that are left after fermentation. So, ideally, I would think you'd have to actually use those types of sugars, in the correct proportions, in order to simulate a finished beer.

That's way too much friggin work for something that probably won't even be accurate enough at the end. Nope. I'm out.

 

[balrog]

I kinda thought so. I started to get queasy about trying when I read that distilled spirits "proof" was allowable to be 15% different than stated on label and realize that without lab grade reagents I was not going to feel confident about anything I could make.

 

[doug293cz]

Both, correct me if I'm wrong, are based on sucrose in solution. It just happens that density isn't as touchy as refraction due to the company of sugars (and not pure sucrose) in typical wort.

I guess what I'm trying to say is that the real benefit I see, anyway, is to be able to get an approximation on the fly - but because of a refract's comparatively greater range of potential swings in readings, I wouldn't want to really use it anywhere but cutoff. I prefer a good hydro for everything else.

But, thanks for thoughts guys, it's what I was asking - do you find them useful enough, basically, to warrant getting one.

Thanks, too, for saying the $30 ones aren't all junk. I'd thought just because I see Northern and others sell ones at $90-ish, and I know that they, like all lab-ish instruments can really run up there, that $90 was a baseline for anything of quality. Can I ask - do you happen to have any specific models you could recommend?

A refractometer responds to ("measures") index of refraction. Brix, by definition, is simply the weight percent sucrose in a sucrose/water solution. The Brix scale in a refractometer is based on a correlation Brix and index of refraction. A hydrometer responds directly to solution density. The SG scale is based on the ratio of the density of the test solution to the density of pure water, at the calibration temperature. So, no the SG scale on a hydrometer has nothing to do with sucrose. However, the Plato scale (on hydrometers that read Plato) is based on a correlation of the weight percent sucrose in a water solution to solution density or SG.

My refract has absolutely no make, model, etc. type markings (I don't know, but suspect this is true for most of the low cost refracts available.) All it has is the Brix scale somewhere in the optics. I paid $100 for mine at the LHBS, before I knew any better. It does work well, seems to be fairly robust construction, and holds calibration well between brew sessions. For reading OG's I have found it to be within +/- 0.0005 SG of a precision hydrometer, using Sean Terrill's default wort correction factor of 1.04. But that's only for lighter beer styles so far (no browns, porters, or stouts.)

Brew on

 

[dmtaylor]

I haven't found dark beers to get any different results with the refractometer vs. lighter colored beers.

Another thought, though..... What makes things more difficult is if there's any HAZE in the wort or beer. When the blue line is fuzzy and not crisp, you end up with more of a range of Brix values instead of something very precise. A phrase like "It's somewhere between 6.2 and 6.5, so I'll have to take the average" is something I've murmured to myself many times, or in fact, probably MOST of the time. Only a wort or beer that is clear as crystal will give you a really precise reading. This adds to the uncertainty even more than it would be otherwise.

 

[balrog]

I haven't found dark beers to get any different results with the refractometer vs. lighter colored beers.

Another thought, though..... What makes things more difficult is if there's any HAZE in the wort or beer. When the blue line is fuzzy and not crisp, you end up with more of a range of Brix values instead of something very precise. A phrase like "It's somewhere between 6.2 and 6.5, so I'll have to take the average" is something I've murmured to myself many times, or in fact, probably MOST of the time. Only a wort or beer that is clear as crystal will give you a really precise reading. This adds to the uncertainty even more than it would be otherwise.

TESTIFY, Brother! I hate it when the blue line's fuzzy. Usually due to the content of the wort, not necessarily the beer content of the person holding the measuring device.

 

[dyqik]

I agree with @dmtaylor on correction factor, but I have worse match even with calcs on FG -- typically off 4-5 points, and most of what I make are 1.050 OG, 1.010-1.015 FG beers.

One thing I'd love to know is how to create a solution that would allow the calculation of what the hydrometer should read and what the refractometer should read. It is fairly simple for OG; add °P amount of sucrose to water. But what about creating a known solution of sugar and alcohol with say 80 proof vodka, sucrose, and water, so that you know the hydrometer should read 1.020 (calc the density) and the ABV is 5% (from the vodka) and then what the refractometer should read. Is that possible?

Yes, it is. A simpler method though is to measure OG with refractometer and hydrometer, then measure FG with both. Something like Beersmith will let you tweak the correction factors until those measurements are all consistent.

Note that Zymurgy a couple of issues back had an article "Revisiting the Refractometer" with new calculations and a nonogram, IIRC based on relations derived and published by the Budvar brewery. These deviate from Sean Terrill's relations, and seem to give good results.

See e.g. https://www.homebrewersassociation.org/forum/index.php?topic=28544.0

 

[user 246304]

A refractometer responds to ("measures") index of refraction, and the Brix scale is base on a correlation of weight percent sucrose to index of refraction. A hydrometer responds directly to solution density. The SG scale is based on the ratio of the density of the test solution to the density of pure water, at the calibration temperature. So, no the SG scale on a hydrometer has nothing to do with sucrose. However, the Plato scale (on hydrometers that read Plato) is based on a correlation of the weight percent sucrose in a water solution to solution density or SG.

My refract has absolutely no make, model, etc. type markings (I don't know, but suspect this is true for most of the low cost refracts available.) All it has is the Brix scale somewhere in the optics. I paid $100 for mine at the LHBS, before I knew any better. It does work well, seems to be fairly robust construction, and holds calibration well between brew sessions. For reading OG's I have found it to be within +/- 0.0005 SG of a precision hydrometer, using Sean Terrill's default wort correction factor of 1.04. But that's only for lighter beer styles so far (no browns, porters, or stouts.)

Brew on

Hey Doug, thanks for the input. Not sure I'm following your 1st line. Brix has no relation to RI - it's simply a mass percentage, namely the percent by weight of sucrose in solution. And sorry, yes, hydro's are simply density meters. I should said in our world, they are based on the relative sucrose density, as you said. I used a salinometer, for cheesemaking. Etc.

In a word, what I'm asking is whether the refractometer, based on the refraction of wort (accept all the givens - sucrose/wort correction etc.), tends to go goofy and give enough imprecision as a working instrument that they are less trustworthy than hydrometers - putatively more robust in dealing with process variables, and giving a decent reading.

Despite this, I do like the comparatively faster read of the refractometer, so think it well suits monitoring runoff. But given my above understandings, is that maybe it, as a "head-to-head" comparison?

Am I posing this well, or is it clear as mud?

Sounds like in your case, the refractometer performs like a champ. Many thanks. Just gathering people's experiences before I drop the coin.

 

[user 246304]

TESTIFY, Brother! I hate it when the blue line's fuzzy. Usually due to the content of the wort, not necessarily the beer content of the person holding the measuring device.

Hahahahahaha...

 

[doug293cz]

Hey Doug, thanks for the input. Not sure I'm following your 1st line. Brix has no relation to RI - it's simply a mass percentage, namely the percent by weight of sucrose in solution. And sorry, yes, hydro's are simply density meters. I should said in our world, they are based on the relative sucrose density, as you said...

Rereading my post, I realized it could have been stated more clearly. I have edited the original, and hopefully it is less ambiguous. Of course Brix is not defined by index of refraction. It's the scale in the refract that is based on a correlation between Brix and RI.

Brew on

 

[ajdelange]

The refractive index of a solution depends on how much of what is dissolved in it and the temperature. The specific gravity of a solution depends on how much of what is dissolved in it and the temperature. A refractometer that reads only RI and a hydrometer that reads only SG are not dependent on any particular substance. When either of them is calibrated in Bx (or, more likely, °P for a hydrometer) there is a dependence on the substance which, in both cases, is sucrose. We measure RI or SG in an attempt to get at the mass of 'extract' dissolved in a kg of wort and we use either the RI to sucrose concentration tables (ICUMSA) or the Plato tables (ASBC/EBC) to do that or, if the manufacturer has provided Bx or °P scales, rely on his consultation of the ICUMSA or ASBC tables to do that for us. Home brewers tend to ignore this preferring to think of 'points per pound per gallon' rather than pounds of extract per pound of wort as the measure of wort strength but advanced home brewers and professionals use Plato with SG to compute pounds of extract per gallon of wort.

The main difference between refractometry and hydrometry is that the specific gravities of solutions of the sugars actually found in wort, which are largely not sucrose, follow the specific gravity of solutions of sucrose much more closely than the refractive indices do. In fact even the density of a solution of soluble starch (high molecular weight sugar) is very close to the density of a solution of sucrose of the equivalent strength. Thus the reading from a hydrometer will always give an accurate assessment of actual wort strength. A Bx calibrated refractometer will often give a reliable measurement but will at times, dependent on the sugar spectrum of the wort you have produced, give one that is off by as much as a couple of Bx.

 

[user 246304]

Thank you AJ. It's sounding like the convenience of a quick read whether for knowing when to cut runnings of or no, isn't really so much of a convenience, if it is undependable. And that the hydrometer's, I don't know what the word is, "robustness," the ability to be a decent predictive tool across a wide spectrum of conditions?, makes it preferable, granting simple taste. That's my take from your post. Is that about right?

 

[ajdelange]

The refractometer is handy for determining when to stop collection because it is so easy to make a measurement - particularly with a digital refractometer (which doesn't suffer fuzzy line syndrome if the wort is turbid because the light never enters the wort). As you are likely to want to stop at 2 - 4 Bx it really doesn't matter that the instrument reads in error by even a substantial percentage. OTOH if you are shooting for 13 °P wort and your refractometer tells you it is 11.5 Bx that has consequences.

 

[user 246304]

Perfect. Thanks AJ, that's what I was wondering. Now I have to think on whether spending for an instrument for basically a single purpose is worthwhile. I've only considered instruments $90 and above but people are saying they've dependable ones at far less. Time for some digging. If you happen to have any digital models (digital always makes me leery - scales, thermometers...but I have to accept the world is new again) you'd feel comfortable recommending, much appreciated. I'd understand fully if you'd rather not dive into that can of worms.

 

[schematix]

I'm interested in hearing about digital refracts too... looks to be another price level over the cheapo ones, but i'm a sucker for nice tools, so why not?

 

[Qhrumphf]

I use refract for a few spot checks where precise accuracy isn't crucial and speed is- during sparging, as well as spot checks in the boil. When more precise is needed, it's a hydrometer. If you collect your sample in a metal vessel (a metal cup for example), and bath it in ice water you'll get to temp very very quickly. As I'm often recording pH at the same time and have to cool it anyway it works out.

Also for what it's worth, irrespective of wort composition the handful of refractometers I have used have always read +/- 0.5°P- and usually less than 0.25°P -from hydrometer (pre-ferment, I will not ever use one post ferment, cannot trust a corrective calculator for my purposes). However I recognize that my case is likely the exception and it does indeed vary device to device.

An acquaintance of mine puts it simply: "refractometers lie". He only uses a hydrometer.

Also I see people saturate the plate with whatever before reading. I find I get more consistent (and consistently readable) results with a single drop.

 

[schematix]

With wort i frequently see occasions where the brix is both higher and lower than the plato measurement. They almost never agree. Not sure why it's both plus and minus, but at the end of the day i go with the precision hydro for my 'official' OG and FG numbers.

 

[Qhrumphf]

With wort i frequently see occasions where the brix is both higher and lower than the plato measurement. They almost never agree. Not sure why it's both plus and minus, but at the end of the day i go with the precision hydro for my 'official' OG and FG numbers.

I say plus minus as one would read barely above, one barely below, etc. However a given refractometer reading inconsistently for a given sample proves a wider swing than that. So in essence I consider them accurate but not precise.

As I said, "Official" is hydro as well. More reliable.

 

[cire]

It's my opinion that the limitation of refractometers is not due to their accuracy, my cheap one is surprisingly good, but the belief that gravity of runnings will universally determine wort quality.

Regardless of obtaining an ideal mash pH, when sparging pH will rise and cause the extraction of those nasties presumed to be retained.

If runnings pH measure more than 5.6, regardless of gravity, they are unsuitable. Only if you match a particular gravity of runnings to when pH is 5.6 is that gravity practical to use to stop collecting runnings.

 

[dyqik]

It's my opinion that the limitation of refractometers is not due to their accuracy, my cheap one is surprisingly good, but the belief that gravity of runnings will universally determine wort quality.

Regardless of obtaining an ideal mash pH, when sparging pH will rise and cause the extraction of those nasties presumed to be retained.

If runnings pH measure more than 5.6, regardless of gravity, they are unsuitable. Only if you match a particular gravity of runnings to when pH is 5.6 is that gravity practical to use to stop collecting runnings.

I think this applies more generally as well. Hitting a specific OG doesn't tell you the FG of the beer or the ABV, although there are some pretty strong correlations. It's still possible to have a mash that is way off in fermentability though. SG isn't really the quantity we'd like to measure from a mash if we could, we'd really like to be able to measure fermentable and unfermentable sugar content, or fermentable extract vs total extract. But SG is the tool that most brewers are used to, and is easy to measure.

Refractometers measure a different mixture of alcohol, sugar content, and so they have a different sensitivity, particularly after fermentation starts. They are less sensitive to FG, I guess, but they are less vulnerable to temperature issues.

The fact that you can determine the OG/initial Brix value from a refractometer and hydrometer reading of the finished beer is pretty cool though.

 

[user 246304]

Hi Cire, good to see you again. And I used both pH (which was actually faster, though I did depend on ATC way too much as I was concerned with pouring "nasty" wort into such a carefully obtained running), as well as taste, to know when to stop. It's so long ago now, I honestly can't remember. It may be that I allowed the wort to cool to take a hydro reading, almost to back up the quicker pH reading. And everything went into the log, of course.

Edit: I went back to a log from 2005, for an "ESB" (Edgar's Special Bitter, after my grandfather in law, who as I write this is struggling with fighting his last days as the fighter he's always been). I confirm that I took both last running pH (5.38) and s.g. (1.011/2.92). I think I would have forgotten this important point, cire, had you not mentioned it. Thanks.