Hydrometer vs Refractometer

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Sudz

Sudz

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I just received a new refractometer which I calibrated in distilled water with my old standby hydro. I also cal'd a second hydro a friend gave me and was surprised to see it was six points higher than my old one.

I mixed up some sugar water and adjusted it's temp to 60*F. I started with 1.090 and measured each device and wrote down the data as things progressed. I changed the concentration by randomly adding water and taking another set of data points. I did this repeatedly to gather a progression of data across a useful range.

I found the two hydros tracked the same from 1.010 to the 1.090 although the newer one held the 6 point margin throughout the range. The refrac tracked within 1 point of the old hydro after cal at 1.000. However, once readings moved above about 1.040 the refrac started to drop points. By 1.090 the refrac was reading 1.081.

This was a bit surprising to me. I hadn't expected to need to use a calibration curve when using the refrac. Bummer.

Have any of you observed this with your refractometers or do I just have a problem device?
 
That's about right. It will change with different worts as well. Mine is +/- 15% or so from my hydrometer with no predicting which way it will swing. As such, it collects dust in the bottom of a bin of brewing equipment.
 
After messing with mine for hours over two years I had less confidence in it every time I picked it up. Might have been a lemon, but I sold it and have never missed it for a second.
 
The refractometer may not be very precise but it's really handy for measuring hot liquids. I think it's fantastic for quick measurements of mash runnings, pre-boil gravity and for making adjustments during the boil. What it lacks in precision it more then makes up for in speed.

Once the wort is chilled I use a hydrometer. Also use the hydrometer for fermenting and finished beer.
 
I won't even use it for pre-boil. If it's off 10% either way, a beer I'm targeting to be 5.5% can either be 4.95% or 6.05%. Way too much of a variance.
 
smizak said:
I won't even use it for pre-boil. If it's off 10% either way, a beer I'm targeting to be 5.5% can either be 4.95% or 6.05%. Way too much of a variance.
Click to expand...

perhaps yours is damaged. I don't think mine is off by that much.
 
maida7 said:
perhaps yours is damaged. I don't think mine is off by that much.
Click to expand...

It reads perfectly with pre-mixed sucrose solutions. It's off with beer wort.

Different sugar concentrations and color affect the reading, so different mash temps combined with different grist bills can skew it either way. I've read articles suggesting you take a refract reading for a couple of brews and average them to get a calibration factor for your brewery...yikes. That is a major hack at best. I'll just stick to my precision hydrometer.
 
Wow..this is an interesting thread..I was considering a refractometer, but I think I'll just stick to my hydrometer from now on...
 
I am not sure what is going on with yours. I just used mine on the last brew and came up with 1.074 on my hydrometer and refractometer
 
passedpawn said:
I think they work great for pro brewers who make the same beer all the time.

For homebrewers, who might go from a small pilsener to a barleywine on successive wkends, refractometers don't cut it. At least not for me.
Click to expand...

Precisely.
 
Sudz said:
I just received a new refractometer which I calibrated in distilled water with my old standby hydro. I also cal'd a second hydro a friend gave me and was surprised to see it was six points higher than my old one.

I mixed up some sugar water and adjusted it's temp to 60*F. I started with 1.090 and measured each device and wrote down the data as things progressed. I changed the concentration by randomly adding water and taking another set of data points. I did this repeatedly to gather a progression of data across a useful range.

I found the two hydros tracked the same from 1.010 to the 1.090 although the newer one held the 6 point margin throughout the range. The refrac tracked within 1 point of the old hydro after cal at 1.000. However, once readings moved above about 1.040 the refrac started to drop points. By 1.090 the refrac was reading 1.081.

This was a bit surprising to me. I hadn't expected to need to use a calibration curve when using the refrac. Bummer.

Have any of you observed this with your refractometers or do I just have a problem device?
Click to expand...

Does your refrac read in Brix or specific gravity?
 
I think I remember reading that refractometers are only accurate below a certain sugar percentage (like 25 or 30%). Of course that would be 25 Plato which is like 1.105 SG so I guess that doesn't matter with nearly all beers/worts.
 
I've been told that refractometers are good usually, at initial gravities. Very close to on perfectly... but as alcohol enters the mix it throws them off. Mines been very close, maybe 1 or 2 points off 1.050 to 1.051 or something like that for a 1.049 gravity on the hydrometer. The one thing you need to realize is that a hydrometer is only perfectly accurate at its calibration temps, and even it can be off at warmer temps from what a 'calibration for temperature' type calculator can do. I've even regularly, with my hydrometer, taken a sample at preboil of about 170degF and taken the gravity, corrected for temps and gotten say 1.030. Then I take it again at 120degF and adjusted and got 1.034, then taken a gravity at 80degF and get 1.038. The closer you get to calibration temps the more accurate your hydrometer reading is. From all I've read, a correctly calibrated Brix Refractometer is MORE correct at higher temps than a hydrometer would be, but as the alcohol goes up, the refractometer's accuracy goes down. There are some good spreadsheets out there that will help account for this, but they seem to only do well for more normal abv beers, not for big beers. I hear the pro brewers use the refractometer and consider it very accurate for preboil and samples of mash, post boil and any other tests prior to pitching. After that, they use the refractometer for quick small samples to see the fermentation progress but always use a hydrometer for final gravities to ensure accuracy. I may be out in the night, and I may have heard only what 'some' brewers do, and so I would definitely love input on what others have heard. I myself have done tests and its always been pretty close on OG, and preboil, but later its definitely a bit off near terminal gravities.
 
jmancuso said:
Does your refrac read in Brix or specific gravity?
Click to expand...

I was wondering if anyone was going mention this.

I have a SG refrac and I really like it. I do take the reading 2 x each time I take a reading (pre-boil, post-chill & TG). All this means is that I use the contents of the eyedropper rather than just 3-4 drops. From time to time I will use the hydro to make certain that the refrac is accurate and so far so good. I enjoy not having to toss away a beer or two to take hydro measurements like I used to. Montanaandy
 
pompeiisneaks said:
I've been told that refractometers are good usually, at initial gravities. Very close to on perfectly... but as alcohol enters the mix it throws them off.
Click to expand...

In what direction is it off once alcohol enters the mix? If it is too high it might be more accurately measuring the amount of sugar in the beer and not the density (I believe this would be called the Real Extract). Since alcohol is less dense than water, once fermentation starts the hydrometer is not a very good measure of sugar content, only density. This is the same reason we talk about "apparent attenuation" as opposed to actual attenuation. Of course, no one really talks about the amount of residual sugar in beer, so the hydrometer is a more useful tool.

If the refractometer is too low, then I am just blowing steam out my a**.:drunk:
 
I have a brix meter and it's always off by 1 or 2 points. Brix reads 1.062 hydro reads 1.064. I do like my brix meter for quick tests of fermenting wort.
 
I find my refractometer to be extremely useful and accurate for determining pre-fermentation gravities. Once fermentation has started, I find it to be less accurate.
I recommend downloading the trial version of Promash, and using the help, search for "refractometer calibration"
It explains that there are two steps to calibration.
The first step is to calibrate it with distilled water. This makes sure that the instrument gives correct basic readings.
The next step is to calculate the "brix correction factor".
This step corrects inaccuracies caused by the wort characteristics.
As passedpawn stated, if you make the same beer every time, this can be accurate; but if you make brews with very different characteristics, it can be inaccurate.
90% of the time, I make pale ales, and with my brix correction factor, the refractometer gives a very accurate indication of the SG. If I make a stout or lager, it may not be so accurate. I don't know how inaccurate because I have never tried comparing the refractometer against a hydrometer with anything but a pale ale.

-a.
 
I use mine during the boil. Main advantage is that you don't have to cool down a large sample.

I'm never all that worried about the exact gravity of my beers. Long as it's close to what I was shooting for, I'm happy. For final gravity, I just want to know that it's done, IOW, not changing any more.
 
jmancuso said:
Are you using brix to SG converter to calculate?
Click to expand...

I use beersmith when I'm by my computer and brewmath on my iPhone. Each has the correct conversion method. OG, SG, and FG.
 
jmancuso said:
Does your refrac read in Brix or specific gravity?
Click to expand...

Wow...

Great discussion guys. My particular Refrac provides both Brix and SG scales. It's also thermally compensated supposedly. It's a well made device and it's difficult to understand how it could be defective... However, it just doesn't cut it for my interests.

For Sale... cheap. Used only on Sundays.... :)
 
dinertime said:
In what direction is it off once alcohol enters the mix? If it is too high it might be more accurately measuring the amount of sugar in the beer and not the density (I believe this would be called the Real Extract). Since alcohol is less dense than water, once fermentation starts the hydrometer is not a very good measure of sugar content, only density. This is the same reason we talk about "apparent attenuation" as opposed to actual attenuation. Of course, no one really talks about the amount of residual sugar in beer, so the hydrometer is a more useful tool.

If the refractometer is too low, then I am just blowing steam out my a**.:drunk:
Click to expand...

I don't know exactly, but if I recall it was way low... I think I'd have an FG from hydrometer saying 1.014 and the refrac would say 1.007.
 
I'm glad this discussion topic came up. I just got a refractometer for Christmas and have been noticing some inconsistencies between it and the hydro as well. I like the experiment that the OP did -- I think I'll pick up another hydro and go through that myself and post the results.

I do a lot of smaller batches and hate to "loose" (I always still drink it of course) those samples for FG testing and that's why I was really attracted to the refractometer. Unfortunately, I'm not really comfortable which the results I'm getting from it yet.
 
I just got a new refrac with ATC and SG scales. It is great for gravity during the boil, but just took a gravity reading after about a week, and it seemed way off. I know you have to use a spreadsheet or something to correct for the alcohol, so I though I would just use the morebeer spreadsheet. Here's the numbers

OG (refrac): 20
Sample (Refrac): 9
Morebeer Corrected SG = 1.008
Hydrometer: 1.018

The spreadsheet was off by 10 points!

It just seems hard to believe there isn't a good correction calculator out there. Is anybody able to use a refractometer for final gravity readings?
 
There is both an adjustment factor for the typical wort, PLUS the calculation for readings in fermenting wort. You need to use a program, like beersmith. Until I did all that, I was way off.

My new hydrometer is worse, as it has a huge offset in distilled water I have to mentally adjust for......
 
rycov said:
how much
Click to expand...

Oops.... I've been out of pocket lately and didn't see this response. I'll probably just hang on to it, why I'm not sure. I definitely would not buy one again however.

Sorry about the tease....:eek:
 
Are the majority of you using the ATC enabled refractometers that measure in gravity as well? Does anyone have any positive experience with refractometers? Usually no news is good news so there's got to be someone who isn't speaking up that's had good results with them...hopefully.
(I'm tired of breaking hydrometers. I break them about once a year/every six months)
 
Sudz said:
Oops.... I've been out of pocket lately and didn't see this response. I'll probably just hang on to it, why I'm not sure. I definitely would not buy one again however.

Sorry about the tease....:eek:
Click to expand...

its cool. i actually ended up buying on. just got it last weekend and haven't used it yet though. i calibrated it in water (actually i just checked it and it was already correct). its the one with ATC and it reads in brix and SG. i'll use it along with the hydrometer for the next few batches and see if i'm ok with the inconsistency/ can figure out a correction factor for it. i'll let you guys know what i find works for me:mug:
 
I have a friend that uses one which is in Brix, not SG. He's actually had fairly good success with it and by and large. He does have a fancy hydrometer that he used to calibrate it first and still occasionally does calibrate it but he by and large uses it with a fair amount of accuracy to check the FG readings. He enjoys not having to waste a half a beer.

I do have plans to get one some day so I'm curious as to what models people have had good experiences with, largely because a couple times I've forgotten to pour off a FG sample and it would be nice to be able to think, oh I'll just pull out the eyedropper and grab a bit off the top right now.
 
oh. i meant for his beer. i was reading where others were saying you had to come up with a correction number to get an accurate reading for wort and a different calculation for fermenting or fermented beer
 
I have a refractometer that I originally got as a hydrometer replacement, but quickly realized that it doesn't work all that well for that purpose, since the ethanol correction formulas and spreadsheets are fairly useless. Someone just recently developed a set of formulas that are supposedly more accurate, but I haven't played with them yet. The link for the new formulas is http://seanterrill.com/2011/04/07/refractometer-fg-results/

A couple of things to note:

Refractometers with a SG scale still need to be corrected by the wort correction factor. Also, Gordon Strong reports that some of them are incorrectly scaled (i.e. the scale is SG=4 Brix, which isn't quite correct).

Refractometers are very useful when quick measurements of hot liquids are required, such as figuring out when the SG of the second or third runnings are starting to run too low, or for a pre-boil gravity reading to verify that starch conversion occurred properly.

Salt water refractometers are useless for brewing. You need a sugar hydro.

Immersing the refractometer into hot liquids can screw up the ATC. Take a sample and drip it onto the refractometer slide, then close it to take the reading.

Make sure that your sample doesn't have any air bubbles or protein/hop particles in it. That can skew the reading quite a bit.

Stir the liquid you are testing to make sure it is well-mixed. Since the sample size is so small, sampling bias is a much bigger problem than with a hydrometer.

Repeat each measurement twice to make sure you get a consistent reading.
 
I'm going to use mine for the first time on Friday. I got the one with a brix and sg scale. It was spot on with distilled water calibration, and it was sopt on with my starter wort 1.036, checked with 3 hydrometers. Fwiw, they are designed to only measure sugar content, not alcohol, I knew this going in. Just hope it's easier than cooling 3-4 wort samples throughout the brew day.

_
 
Another thing to note here. ATC is meant to correct for varying ambient temps but NOT varying sample temps. The sample has to be the same temp as ambient for it to read accurately immediately, otherwise you have to give the prism/body some time to pull the heat out of the sample. The one issue you have if you let it sit for too long is that some of the water can evaporate out of the sample creating an artificially high reading.

Here's what I do. When I pull a sample into the pipette, I make sure it's a very small amount. Then I shake it bulb side down in a cup of icewater for 5 seconds before dropping the sample on the plate. Now it's closer to ambient temps and will be more accurate.
 

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