Author: Marshall Schott
I’d reckon most of us own (and have broken) a hydrometer or three. I received my first one in the kit I purchased at the genesis of my obsession with this hobby. It’s a fantastic tool that allows us to determine fairly accurately how much sugar is in our wort/beer based on its density (click here for a more thorough explanation), thereby providing the ability to predict the percentage of alcohol in our finished beer. Some people don’t care, which I appreciate, though can only barely relate with because I like knowing stuff like final gravity (FG) and the ABV of my beer. As helpful as they are, hydrometers do have some downsides. Since they’re made of thin glass, they are fragile and very easy to break. They also require a fairly sizable amount of wort, at least enough to fill a hydrometer jar about 75%, and the liquid has to be a specific temperature to provide the most accurate reading. After doing some research a few years ago, I discovered another tool purported to provide similarly accurate measures of specific gravity while requiring a significantly smaller sample of wort and it also had the ability to automatically correct for temperature: the refractometer.
Whereas hydrometers measure specific gravity (SG) based on the density of a liquid, refractometers determine SG using refraction of light. Basically, light is passed through a very small sample of wort and the extent to which that light refracts (bends), called the refractive index, allows us to predict the amount of sugar in our wort. I shopped around for a bit and ultimately settled on the refractometer I currently use today.
There are a ton of options out there ranging drastically in price, though all look and appear to function very similarly. My guess is they’re all likely made by the same factory in another country. I chose the one I did because, at less than $30 shipped, I felt like I could justify the purchase as an interesting experiment if it didn’t work, plus I really liked that it was dual-scale, providing measurements in both both brix and SG, no conversion needed. I was definitely skeptical this product wouldn’t be nearly as accurate as my trusty ol’ hydrometer. I’d heard of a few folks who simply couldn’t get their refractometers to match their hydrometer readings and who ultimately ended up shelving the unit for what they knew worked. But I had to give it a shot. I was certainly enticed by the very dorky idea of being able to measure the SG of my wort using a single drop at any point during the brew day.
Given my doubt, I spent probably too much time researching the pros and cons of refractometers during the 2 day period between ordering and receiving the unit. I’ve already discussed many of the pros, most of which can be summed up as “ease of use.” It was the cons, which were few and far between, that got me worried. Some people seemed to get similar readings from multiple samples of the same wort, others complained about how their refractometer samples were never aligned with their hydrometer readings, and most frequently was the concern that refractometers were terrible at providing final gravity readings. Had I made a mistake?
I received my refractometer and immediately began playing with it, first by calibrating it using a drop of pre-boiled water– either my water was slightly fermentable or my refractometer was out of whack. Using the small adjustment screwdriver that was included in the package, I made the proper adjustments so the water read 1.000 SG (0 brix). I tested it again using tap water, bottled water, and hose water, all of which resulted in the same 1.000 reading. Cool. I then measured the SG of my kids’ apple juice multiple times and it came in at 1.048 on each attempt. Watered down maple syrup, juice squeezed from a lemon, saliva– all came back with similar results on each measure. At this point, I felt confident in the consistency of the product. It was time to put it to the test on a brew day. I made a batch of wort and, for the first time, measured my pre-boil OG, something that felt like a hassle with a hydrometer. There was something exciting about knowing I’d hit the numbers predicted by BeerSmith. Once the boil was complete and the wort was chilled, I drew off a hydrometer sample to compare with the refractometer sample and found they were exactly the same. I’ve done this many times since and continue to get similar results.
As far as using a refractometer pre-fermentation, I was sold, it was so easy and accurate. The time came on that first batch to check FG, which I was convinced wouldn’t be accurate at all. I measured SG using both tools and, sure enough, they were remarkably different. While the hydrometer indicated I’d reached my target FG of 1.012, the refractometer was reading something closer to 1.024 (6.1 brix). I learned that alcohol impacts the refraction of light, hence the inaccurate reading, and that there were ways to calculate for that impact to determine a more accurate FG using a refractometer. Back to Google I went, searching for a calculator that would allow me to enter the information obtained from my refractometer and spit out a FG that matched my hydrometer. Rather quickly, I stumbled on Sean Terril’s killer website where he has a refractometer calculator that appeared to do exactly what I was looking for. His calculator requires brix, which was fine since my refractometer is dual-scale. I plugged in all the required information, pressed calculate, and the estimated FG came out to 1.0117, close enough to the 1.012 my hydrometer indicated to make me a believer. I’ve tested Sean’s calculator numerous times since and have always yielded similarly accurate results. Still, I’ve tended to stick to measuring FG with my hydrometer, mostly because I enjoy sampling the beer before packaging. If you’re concerned about FG measurements with a refractometer, know that it is absolutely possible using a good calculator.
All in all, I really like my refractometer and use it multiple times every time I brew, I’ve absolutely no regrets with this purchase. I’ve easily used it over 100 times with no issue. It has a solid feel and has proven to be quite durable. If mine were to break, I wouldn’t think twice about purchasing the same one again. Is it necessary? Not at all. But it certainly is functional and I’d argue it does increase the ease of a brew day. For those who struggle to get consistently accurate results, here’s what I’ve found seems to work pretty well:
– Calibrate the refractometer using pre-boiled or bottled water every brew day.
– Make sure your wort is mixed really well before pulling a sample, especially if you brew with extract.
– Use a brewing spoon to collect wort, allow a couple drops to fall onto the sample plate, then put the cover down and gently tap to evenly disperse the liquid.
– If the sample is from hot wort, either gently blow the plate for a few seconds or let it sit for about a minute to stabilize the temperature of the wort before taking a reading.
– Rinse and dry the refractometer immediately after every use.
That’s about it. I’m not sure I’m doing anything special, but my refractometer readings are usually spot-on with what BeerSmith predicts as well as what my hydrometer indicates. And that works for me!
Follow Brülosophy on:
FACEBOOK | TWITTER | INSTAGRAM
| Read More |
18 Ideas to Help Simplify Your Brew Day
7 Considerations for Making Better Homebrew
List of completed exBEERiments
How-to: Harvest yeast from starters
How-to: Make a lager in less than a month
| Good Deals |
10% Off Chapman Equipment ThermoBarrels using code: THINKBEERDRINKBEER03
Brand New 5 gallon ball lock kegs discounted to $75 at Adventures in Homebrewing
ThermoWorks Super-Fast Pocket Thermometer On Sale for $19 – $10 discount
Sale and Clearance Items at MoreBeer.com
If you enjoy this stuff and feel compelled to support Brulosophy.com, please check out the Support Us page for details on how you can very easily do so. Thanks!
19 thoughts on “Refractometers | Are They Really Worth It?”
When are they going to build a refractometer that has a final gravity mode, to do what that calculator did?
You can’t do that, because it varies with the amount of alcohol in the beer, so it would need to be a massive sliding scale.
Do you have any comments on the quality of the automatic temperature compensation of the refractometer you linked?
I think it’s funny the term “automatic” is used, as that causes me to envision some machine that automatically corrects the temp. If you take a reading immediately after dropping boiling wort on the refrac, then take another look a minute later, the first reading will be slightly lower than the second. I’ve never used a non-ATC refractometer, but I’d imagine there isn’t much of a difference. I always blow the sample in the refrac for a few seconds before trusting the reading, just to be sure.
I always thought that ATC referred to the automatic correction of the difference between the refractometer’s temperature and the calibration temperature (20C for mine). None will correct for the sample temperature as the heat capacity is very low, its only two drops of wort, and will thermalise with the body rapidly.
However I must add that I have also never used a non-ATC refractometer.
Well, well… I just learned something very interesting. Thanks!
I got a refractometer forever ago, and just never saw the utility of it. Recently, I decided it would be nice to start measuring pre-boil SG and make adjustments to my boiling/ hopping schedule to compensate if I missed my numbers a bit. Not only is it a pain to measure this with a hydrometer, it takes so long to cool enough wort that I would be rushed to make the adjustments I want.
I think the difference between refracts and hydrometers is usually a calibration issue, but I would think high amounts of protein and starch in the wort might also throw off the readings, since refracts only measure sugar. But, I’ve never had time to do further research on that theory…
– Dennis, Life Fermented Blog
One thing I’ve noticed using my refractometer is that it drifts if its temperature changes significantly after initially zeroing it with tap water. I other words, don’t leave it sitting out in the sun between measurements! (In all fairness, too much sun is only a “problem” in Seattle a couple times a year.)
Do you notice any difference with the FG on Sean Terril’s killer website and the calculator in BeerSmith?
I’ve actually never compared them.
My only issue is that when I compare the results across the 3 calculators I’ve tried (Sean Terrill’s, Northern Brewer, Brewer’s Friend) I get wildly varying FG numbers…enough to swing ABV by 1-1.5%. I just bought a new hydrometer after relying on my refractometer solely for a while after the last hydrometer broke.
Compare all 3 to the hydro reading, stick with the one that is closest. Sean’s was that for me.
In case you didn’t realize it, the refractometer you are linking to on Amazon is not sold by Agriculture Solutions LLC, nor is it even manufactured by A.S. as witnessed by the Amazon reviewers who have tried to get a warranty service. It’s simply a Chinese counterfeit, like scads of other crap for sale on Amazon. No, Amazon doesn’t care as long as people keep buying and you keep referring them.
Here’s the real one, by the way. It’s no doubt worth the few extra bucks, if only for the warranty.
(http://www.agriculturesolutions.com/products/crop-soil-and-water-testing/refractometers-brix-meters/dual-scale-beer-and-wine-refractometer-s-g-0-32-brix-detail)
OK, this is a really old post but I can’t find shit on this anywhere:
I’ve been using my refract for nearly 2 years. Every once in a while, I’ll check it against my hydro just to make sure it’s accurate (pre and post fermentation). It is. I mean dead-on accurate.
So I share my zeal of refractometers with other homebrewers and I’ve head many of them say, “I have to recalibrate mine every time I use it.”
So my question is, why? What he hell goes haywire with a glass prism? What inside those things gets mis-adjusted between brews?
Or are they just full of it?
Don’t know if you still read this, but I noticed something – if you look at the picture at this review 20 Brix corresponds to about 1.083 SG, but if you look at the picture of refractometer here:
https://brulosophy.com/2017/09/11/the-impact-of-cold-side-oxidation-on-new-england-ipa-exbeeriment-results/
20 Brix there is 1.077 SG – 5 points difference. Do you know why? I assume it’s a different refractometer (and it’s the same scale that I have and it is different from online calculators that say 20 Brix is actually 1.083).
Hey! Apparently, my refractometer is inaccurate after about 1.065 OG, which is when I’ll use a hydrometer to confirm.
Well, so much for the Sean Terrill calculator. You enter brix and it takes you to a BS generic synthroid site.
How do you take good pictures of refractometer readings?
iPhone, a steady hand, and some cropping.