refractometer question

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kranak

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I have noticed something that is odd to me when measuring the og with my refractometer. Like I am sure most are, it has brix on the left side and gravity points on the right. An example of what is messing with me is this. Todays beer ended with a brix of 23, which on the right side of the refractometer reads about 1.088. When I compare 23 brix to online tables or enter that amount in the refractbeer excel sheet it says I am closer to 1.096.This is with og measurement so no fermentation has occurred. Which one is right?
 
Odd, it the printed scale. Nothing to be calibrated, or that can move. It would be odd but completely possible that it was printed incorrectly.
 
kranak said:
Odd, it the printed scale. Nothing to be calibrated, or that can move. It would be odd but completely possible that it was printed incorrectly.

I am checking mine out as we speak. I grabbed the dual scale from homebrewfinds.com. using it yesterday I had a similar discrepancy. Luckily I had my old brix-only unit to fall back on.
 
I calibrated both refractometers with 68F water and did some measurements. My old one is dead nuts accurate. The dual scale brix side was pretty darn close...but the SG scale was completely off. Yes I could have checked that just by looking at the scale without even taking a sample but I wanted to check everything. So, brix side, very close. SG side - ignore. No wonder this thing was $24.95. I got this off of ebay and will get no refund, but you might want to talk to AHS as they are a reputable store on the off chance that you just got a bad one.

I have to say one positive is that the scale inside when you are viewing is huge...it's much larger than my original unit, so it reads easier. I'll probably use it just because of that. How's that for putting whipped cream on horsesh*t?
 
The brix scale is a measure of the amount of sucrose in a solution. Wort contains very little sucrose, but relatively large amounts of maltose and maltotriose. The conversion from brix to S.G. is different for a wine must (almost 100% sucrose) and beer wort (mainly maltose and maltotriose). Because of this, it is not possible to have a S.G. scale on the refractometer that is accurate for both beers and wines. Most refractometers with a dual scale have an S.G. scale calibrated for wine, but there may be some where the S.G. scale is calibrated for beer. Even if you have one that is calibrated for beer, the calibration will change slightly, depending on what went into the wort.

-a.
 
Ill send a note to Austin, but at least I know to read the brix side. I broke my hydrometer so I had nothing to check against.
 
The brix scale is a measure of the amount of sucrose in a solution. Wort contains very little sucrose, but relatively large amounts of maltose and maltotriose. The conversion from brix to S.G. is different for a wine must (almost 100% sucrose) and beer wort (mainly maltose and maltotriose). Because of this, it is not possible to have a S.G. scale on the refractometer that is accurate for both beers and wines. Most refractometers with a dual scale have an S.G. scale calibrated for wine, but there may be some where the S.G. scale is calibrated for beer. Even if you have one that is calibrated for beer, the calibration will change slightly, depending on what went into the wort.

-a.

I did not know that. Interesting. So brix is actually a wine-making scale. Professional brewers use Plato if I understand it correctly, and we homebrewers use SG. I have wondered why there were so many scales, this provides at least one answer. :mug:
 
SG measures the density of the liquid not the sugar content. So is you dissolved table salt in distilled water you will see an increase in SG but not in Brix. So if you try and calibrate your SG scale with tap water that has minerals and other things dissolved in it you will have a positive reading on you SG scale. Now if you take lab grade distilled water and did the same calibration you should end up with 1.000 SG and 0 Brix. Just remember that 1.000 SG is the gravity of pure water.
 
I need to re-read this thread but just checked my refractometer scale. Brix scale on left SG on right. On mine, 23 = 1.090.
 
I need to re-read this thread but just checked my refractometer scale. Brix scale on left SG on right. On mine, 23 = 1.090.

Mine reads close to that, I'd call it 1.088 like the OP. Problem is, my conversion chart says 23 should be 1.096.
 
Yes, as ajf already pointed out. Some of us are just learning that. We are comparing readings on refractometers because apparently they are not all calibrated the same(?)
 
I just wish someone would release an inexpensive refractometer that simply displayed refractive index. These "pre-calibrated" Brixes and SGs are more misleading than helpful.
 
I understand now the fact that these aren't calibrated for beer. It just would have been nice for that to be a little more plainly stated. Like the fact that these don't directly work after fermentation has started. That is widely talked about and stated in the included instructions. I boiled yesterday's beer for nearly an extra hour trying to get to my desired gravity. Then found out that wasn't needed and now I'm about six points over. I assumed the gravity scale functioned in for beer.
 
Bobby_M said:
It looks like you may have a dud scale there. The units I have put 23 brix at around 1.096 also.

Bobby are you selling units that have the correct SG scaling, ie scaled for beer not wine?
 
I have one of the refractometers that Bobby sells. When I first received it I used some distilled water to calibrate it. Then I compared the same water with my hydrometer so that I knew the readings would be the same. After that for 12 batches or so I kept notes on both the refractometer and the hydrometer reading. What I found was that they were off by maybe one or two gravity points.
 
I calibrated both refractometers with 68F water and did some measurements. My old one is dead nuts accurate. The dual scale brix side was pretty darn close...but the SG scale was completely off. Yes I could have checked that just by looking at the scale without even taking a sample but I wanted to check everything. So, brix side, very close. SG side - ignore. No wonder this thing was $24.95. I got this off of ebay and will get no refund, but you might want to talk to AHS as they are a reputable store on the off chance that you just got a bad one.

I have to say one positive is that the scale inside when you are viewing is huge...it's much larger than my original unit, so it reads easier. I'll probably use it just because of that. How's that for putting whipped cream on horsesh*t?

Just use the Brix scale then BeerSmith or another conversion tool to convert it to SG. Most tools allow a conversion for both unfermented and fermenting. For fermenting, you will need to provide the OG to get an accurate conversion.
 
I understand now the fact that these aren't calibrated for beer...
I have an ebay one. I checked it and sure enough 23° brix = 1.088(ish). Funny thing is my 2 scales are Brix 5 and WORT SG
So it is not a matter of explaining that these are calibrated for wine but that some of them are just plain wrong :D
Thanks for bringing this to our attention, I am now converting to use °Plato/°Brix for my messurements.

The funny thing is it is being said that the reason these are wrong is because they are calibrated for wine, well I chcked (ok only one) conversion calculator from a wine making website and it too said 23° Brix = 1.096
http://vinoenology.com/calculators/fermentation/
 
Yep, I have a conversion table taped to the cabinet in the brew room and that's how I'll use it. I don't really use it for post-fermentation, after all I need to drink the hydrometer samples!

But seriously there was some other thread going in here the other day where a couple of professional brewers were talking about these super accurate instruments...some kind of hydrometers but commercial grade, where you needed to use three of them to cover the whole range of potential gravities. I know +- a point or two will not matter to homebrewers, but it would be nice to know for sure where your tools are off a bit and a tool like that would do it. Does anyone know the name of those?
 
But seriously there was some other thread going in here the other day where a couple of professional brewers were talking about these super accurate instruments...some kind of hydrometers but commercial grade, where you needed to use three of them to cover the whole range of potential gravities. I know +- a point or two will not matter to homebrewers, but it would be nice to know for sure where your tools are off a bit and a tool like that would do it. Does anyone know the name of those?

They're still called hydrometers, but if you buy them off of a laboratory supply company you'll have a wide diversity of ranges available to you.

If you're looking for some, cynmar.com has reasonable quality gear for cheap(ish) prices. If you're feeling very ambitious, you could always roll over to Fischer Scientific.
 
So I ran a small experiment.

Last night, I made two small solutions, one consisting of sucrose (table sugar) dissolved in water, and the other consisting of Munton's extra light DME dissolved in water.
In each case, I used about 4 oz water, and about 40g of sucrose or DME, and the Brix readings came out > 23 Brix.
I then diluted the solutions with water until I got a reading of 23 Brix, and put them in the fridge to cool down for some hydrometer readings the next morning.
Next morning, I took the samples out of the fridge and waited for them to warm up to 60F so I could take hydrometer samples with a triple scale hydrometer.
Meanwhile, I calibrated the hydrometer and determined that it was reading two points low.
The gravity reading of the sucrose solution was 1.095 + 0.002 = 1.097
The gravity reading of the DME solution was 1.088 + 0.002 = 1.090
Bear in mind that I'm not using lab grade equipment, my eyesight is not as good as it used to be, and I have a sample size of 1, so there could be some minor inaccuracies in my readings
.
The gravity of the sucrose solution is very close to the 1.096 reported before, matches the standard translation for Brix to S.G. assuming the solution contains 100% sucrose "Specific gravity = (Brix/(258.6-(Brix/258.2)*227.1))+1"
All of the on-line converters and tables that I have seen use this algorithm or something very close.
If you have a dual scale refractometer, and 23 Brix is equal to 1.096, then the S.G. scale is suitable for wine, but not beer.

The gravity of the DME solution is fairly close to the 1.088 reported by some posters, so perhaps those refractometer scales are calibrated for wort, rather than wine. However, it is also possible my reading was wrong, and that if I had made the sample my mashing some grains, I would have gotten a different conversion. I do know that if I convert 23 Brix to S.G. using Promash I get a S.G. of 1.092. The Promash conversion divides the Brix value by a "Brix Correction Factor" before performing the conversion, and this factor was determined by taking Brix and Gravity readings from several All Grain brew sessions.

Hope this makes sense.

-a.
 
...The gravity reading of the sucrose solution was 1.095 + 0.002 = 1.097
The gravity reading of the DME solution was 1.088 + 0.002 = 1.090
Bear in mind that I'm not using lab grade equipment, my eyesight is not as good as it used to be, and I have a sample size of 1, so there could be some minor inaccuracies in my readings
.
The gravity of the sucrose solution is very close to the 1.096 reported before, matches the standard translation for Brix to S.G. assuming the solution contains 100% sucrose "Specific gravity = (Brix/(258.6-(Brix/258.2)*227.1))+1"
All of the on-line converters and tables that I have seen use this algorithm or something very close.
If you have a dual scale refractometer, and 23 Brix is equal to 1.096, then the S.G. scale is suitable for wine, but not beer...
-a.

That is awesome ajf :mug:
Ok before i completely write off my refractometer's sg scale I will actually trial it with samples from my next few brews.
Cheers!
 
Interesting there... My scale is 1.088 for 23 Brix..

Will do some of my own testing with it, and try it out.
 
Interesting there... My scale is 1.088 for 23 Brix..

Will do some of my own testing with it, and try it out.

Yeah, don't take my word for it, try it for yourself. I'm not being rude when I say this, I really encourage anybody who is interested to do the experiment for themselves if you have a refractometer with dual scales and an hydrometer.

I only have a Brix scale, but I will do the experiment with a full size AG batch using one of the on-line converters or tables next time I brew.

-a.
 
Thanks for the thought and insight on this. The difference didn't really jump out at me on averaged sized beers. The refratometer was maybe .01 or .02 off from the spread sheet. This was my first large beer using it so it got me wondering. .08 difference is big enough that it had me changing my brew day. Working from the brix side is easy. An extra thirty seconds of notes before my brew day and I'm good.
 
Yeah, don't take my word for it, try it for yourself. I'm not being rude when I say this, I really encourage anybody who is interested to do the experiment for themselves if you have a refractometer with dual scales and an hydrometer.

I only have a Brix scale, but I will do the experiment with a full size AG batch using one of the on-line converters or tables next time I brew.

-a.

Just out of curiousity, after you diluted to 23 were the volumes significantly different?
 
If you have a dual scale refractometer, and 23 Brix is equal to 1.096, then the S.G. scale is suitable for wine, but not beer.

The gravity of the DME solution is fairly close to the 1.088 reported by some posters, so perhaps those refractometer scales are calibrated for wort, rather than wine.

This is exactly my understanding of how refractometers which are scaled like this (as mine is) are intended to work.

When using a refractometer calibrated for sucrose, you will get a higher Brix reading than you actually have, due to the refractive indices of wort and a sucrose solution of the exact same gravity being different. This error is usually between 2 and 6 percent on the high side.

So if you have a brix reading of 23, that would come out to around 1.097 if you used the value straight up. But if you divide by 1.06 you get 21.7, which is around 1.091. Admittedly, this is using the high end of the error, and still is higher than 1.088... but if the Brix scale is intended to measure sucrose and the SG scale is "calibrated" (and i put calibrated in quotes because it would be based on an assumed wort) to measure wort, then they should be offset by a bit.

http://***********/stories/projects-and-equipment/article/indices/29-equipment/1343-refractometers
 
Just out of curiousity, after you diluted to 23 were the volumes significantly different?

It was a very small sample, slightly over 4 oz, and I measured the water volume using a 1/2 pint jug with markings at 2, 4, 6, and 8 oz. I don't doubt that the volumes were slightly different, but a very small volume difference in a 4 oz sample could be significant. Both samples fitted in to my hydrometer test cylinder filled nearly to the top. If I'd known you were going to ask this question, I would have weighed the samples, but I didn't. I think I can safely say that the sample sizes were within 10% of each other.

-a.
 
If we're talking about Bobby's refractometers. My humble opinion is this:

Bobby_M does not put out products he has not researhced, proved and believed in. I did get my refracotmeter from him. It might be off, very slightly. Very slightly! But for the price he charged I' be a fool to complain. The thing works extremley well in my opinion.

I enjoy buyinj his products, especialy the one's he makes himself. Bobby's equipment is great in my opinion. He doesn't charge and arm and leg for his stuff and his products work extemely well.

The other day I was looking arournd for quick disconnets (QD's) for my brewery. I checked many places. What Bob sells f0r $4 cost 100% more on those sites.

From me... thankyou Bobby for not only the enormous amount of brewing info you have put out for free for homebrewers. But, Thankyou for great products and great pricing. Nobody ive seen selling beer stuf here has the heart, quality, or great pricing that you do.

Just my humble opinion.

Cheers Bro!

Dan
 
If we're talking about Bobby's refractometers. My humble opinion is this:

Bobby_M does not put out products he has not researhced, proved and believed in. I did get my refracotmeter from him. It might be off, very slightly. Very slightly! But for the price he charged I' be a fool to complain. The thing works extremley well in my opinion.

I enjoy buyinj his products, especialy the one's he makes himself. Bobby's equipment is great in my opinion. He doesn't charge and arm and leg for his stuff and his products work extemely well.

The other day I was looking arournd for quick disconnets (QD's) for my brewery. I checked many places. What Bob sells f0r $4 cost 100% more on those sites.

From me... thankyou Bobby for not only the enormous amount of brewing info you have put out for free for homebrewers. But, Thankyou for great products and great pricing. Nobody ive seen selling beer stuf here has the heart, quality, or great pricing that you do.

Just my humble opinion.

Cheers Bro!

Dan

I'm not talking about Bobby's instruments as I don't have one.

My experiment showed that there was a 7% difference between a sucrose solution and a DME solution, and if I use a calculator or lookup table such as
http://www.brewheads.com/brixsg.php
http://www.brewersfriend.com/brix-converter/
http://www.winning-homebrew.com/specific-gravity-to-brix.html
http://onebeer.net/refractometer.shtml
or articles such as
http://***********/stories/article/...y/1344-refractometers-and-mash-outs-mr-wizard
then I get a 7% error when using a refractometer to estimate the specific gravity of wort.
It is quite possible that some refractometers report a true Brix value (or close) when measuring wort, but they would be wrong when measuring must.

As I said earlier, I think the most sensible thing to do is to check the refractometer reading against an hydrometer reading for what you use the refractometer for, and decide if any errors are acceptable to you.

One thing did surprise me was that I got a 7% difference, but when I calculated the Brix Correction Factor for Promash, I only got about a 4% difference. This could be because of an extract based sample with no specialty malts vs an All Grain sample. It could also be a measurement error on my part based on a sample of 1, or it could be because the refractometer has drifted over time. I will be taking more measurements to try and identify the cause of the difference.

-a.
 
It's not really a question of Bobby's equipment so much as fundamental facts of physics. Bobby makes/sells great gear, but he can't change the nature of the universe (yet....).

We're trying to convert between an optical property of wort and a density property of wort, and that relationship is inherently complex. No scale will always be right, and any "built-in" calibration is going to be made on the basis of a very particular set of assumptions.

I've tracked my refractometer over a few dozen batches now and on average I've needed to bump my refractometer reading up by about 5% to match my hydrometer, though on any given batch that number has ranged from 3% to 7%. That's plenty good enough for me to monitor the mash, but certainly if you want a precise measurement of gravity you need to use a device designed for measuring density, not refraction.
 
OK now I am confused. I thought that the inaccuracy came from the calibration of the SG side compared to the Brix, but that the Brix side was still accurate for wort. Are we now saying the Brix side has up to 7% error? When I first used my old refractometer I compared it to a hydrometer reading and it matched. I just assumed from then on it was accurate.
 
...
But seriously there was some other thread going in here the other day where a couple of professional brewers were talking about these super accurate instruments...some kind of hydrometers but commercial grade, where you needed to use three of them to cover the whole range of potential gravities. I know +- a point or two will not matter to homebrewers, but it would be nice to know for sure where your tools are off a bit and a tool like that would do it. Does anyone know the name of those?

They're still called hydrometers, but if you buy them off of a laboratory supply company you'll have a wide diversity of ranges available to you.

If you're looking for some, cynmar.com has reasonable quality gear for cheap(ish) prices. If you're feeling very ambitious, you could always roll over to Fischer Scientific.

Williams Brewing used to sell a three piece set as well. Now they sell a "bottling" hydrometer with a scale of 1.000-1.040 and a "precision" hydrometer with a 1.000-1.100 scale. Most cheap hydrometers go 0.980-1.130.
 
OK now I am confused. I thought that the inaccuracy came from the calibration of the SG side compared to the Brix, but that the Brix side was still accurate for wort. Are we now saying the Brix side has up to 7% error? When I first used my old refractometer I compared it to a hydrometer reading and it matched. I just assumed from then on it was accurate.

Short answer: yes, that's what I'm saying.

Long answer:

Brix is a unit that describes the concentration of sucrose in water. A 20 Brix solution is, by definition, exactly 20% sucrose by weight.

SG, on the other hand, is a measurement of density relative to water. A 1.080 wort will weigh exactly 1.080 times an equivalent volume of pure water, again by definition.

(Plato is an interesting hybrid measurement, but for our purposes you can just consider Brix and Plato to be equivalent).

What a refractometer measures is neither concentration nor density, but rather optical refraction. When you send light through a solution, it bends, and different kinds of solutions bend light to different degrees. What makes a refractometer useful is that the relationship between sucrose concentration and refraction is very predictable. A refractometer does not measure sugar concentration directly, but it measures something else that can be converted to sucrose density in a reliable and predictable way.

Unfortunately, we don't make sucrose solutions. We make wort that includes a wide mix of various sugars and other substances. All these different substances affect the refractive index of wort in different ways. A maltose solution refracts differently than a solution of dextrins, and both of these are different than sucrose. In most worts, the measurements are "pretty close", but there's no way to produce an exact conversion from optical refraction to concentration or density without knowing exactly the composition of the wort. That's not possible without serious lab gear and a test procedure far more complicated than using a hydrometer.

At the end of the day, there is always going to be an inherent uncertainty to converting between the optical properties and density properties of wort. On average, I find that bumping up my Brix reading by 5% or so gets me a value that is close enough to a hydrometer measurement that I don't worry about it. If you are trying to track density more precisely than that, you won't be able to do it with a refractometer. It's just a hard constraint on the nature of the universe.

(As a side note: If 2-3% measurement error is too much, what are you trying to track? Efficiency? ABV? Attenuation? In all these cases, there are other inherent limitations on measurement that introduce as much or more error than a refractometer will. In any system, your data is only as precise as your least precise measurement. For most people, that least precise measurement won't be gravity.)
 
OK now I am confused. I thought that the inaccuracy came from the calibration of the SG side compared to the Brix, but that the Brix side was still accurate for wort. Are we now saying the Brix side has up to 7% error? When I first used my old refractometer I compared it to a hydrometer reading and it matched. I just assumed from then on it was accurate.

The real point is that no refractometer can accurately measure the density of all worts, because wort is not consistent, and you're not directly measuring density. Sucrose is easy, because sucrose is always sucrose, so there's a more reliable correlation between refraction and density. Different worts will have different compositions of sugars, color components, etc, and therefore two worts of the same density can have different refractive indices, and will therefore read differently on a refractometer.

What I do is take a preboil sample and then measure with both my hydrometer and my refract. Usually the offset is a few gravity points. I then use the refract through the rest of the boil, applying the offset. This is a simplification, as the offset wouldn't stay constant, but i figure its close enough. :p

EDIT: What MalFet said.
 
OK, I get it. No I don't need to take 99.99% accurate readings, I'm just trying to understand if and where the measurement is off. Sounds like an adjustment is in order.

These things should come with disclaimers.
 
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