Refractometer Accuracy Testing for Homebrewers 

A follow up to this video is coming on the 1st of November, where I test two high gravity samples.

Thanks for doing this. If I may suggest, I would have liked to also see the reading of your wort from a standard hydrometer, as comparison with the more technical devices, because using one is so cheap. Plus some approximation of the differing costs between devices (e.g. SmartRef is generally 10x price of NoBrand, or something similar) - as lower margin of error is expected as price increases. Just a suggestion, perhaps in the notes.

Thanks, David! Would have loved to see a standard hydrometer reading as well for comparison. Maybe next time. Cheers 🍻

Thanks for making this David, I think these are really interesting little tests and evidently from the comments is super helpful to folks and a very popular format. One (unsolicited) suggestion for the follow up video you’re planning would be to, in addition to using wort, make up a range of different gravity solutions across the typical brewing range using distilled water and sugar so you have values of a known quantity (after applying wort correction factor) as in this video we are using the SmartRef as our reference measurement without having verified this against a set of known values across the intended range. The SmartRef may well have the advertised accuracy, but it would be dead simple to prove it in the interests of completeness and best scientific practice I look forward to the follow up, thanks again Cheers!

Top work. Thanks for this video David. Everyone loves a good side by side comparison.

Great comparison, David!

I use the cheaper one like you showed. I first calibrated it for plain water but when I tried using it with my hot wort that had full starting gravity it was way off by comparison to my hydrometer. So when the wort was cooled down I calibrated the refractometer to match my hydrometer. Now several brew batches later it still matches my hydrometer at full starting gravity.. however it reads way to low on plain water. I have also learned that it reads about one brix too low when the wort is hot but it seems consistent in that way. So for me only needing to read wort with full gravity it works great. thanks for the video.

I use a cheap(ish) refractometer for all my readings, correcting for alcohol content as necessary. Whilst this may not be perfectly accurate, it is certainly good enough to warn me of any problems during the brewing process.

Hi David like most of your videos this was very comprehensive thank you. For my part I I use a cheap blue box refractometer and to be fair to it for the price it is excellent. I used my hydrometer to standardise my refractometer. I chose three different sugar concentrations and check the hydrometer zero using distilled water my hydometer was surprisingly accurate! I have to be honest my refract did not show a reading more than 0.001 sg at any of the three chosen sugar concs. I further used my hydrometer and refractometer over several mashes taking samples at different intervals. After taking some twenty diferent sample readings over various brews I could not split my hydrometer and my refractometer by more than 1 to 2 points . So my take is that for the average home brewer a cheap blue box refract is adiquate we are not selling a product and if the error is so small calculated ABV values will not be badly effected.

Interesting and suprising 👍

I use a generic blue box refractometer while brewing just for a guide but use a conventional hydrometer for taking my actual readings, I certainly don't rely on the refractometer due to its suspect accuracy. Call me old school but I do prefer a hydrometer and can't really justify the expense buying a digital one.

I use a bluebox refractometer for all my readings (during brewing and fermenting), but enter the brix into the Refractometer/Brix correction tool in Brewfather. I have determined my correction factor to be 1.04 by following the procedures laid out by Short Circuited Brewers. This seems to work for me just fine. Sure would like to have one of those Smart Refs though...

It would have been really good to see these comparisons but with temperature differences as one of the big bonuses with the refractometers is that you can use high temp wort (assuming your refrac has temp adjustment)

Thanks for this video. It's been one I've been looking for a while. As an owner of a small brewery that has just started up I have been relying on a hydrometer to this point as unfortunately the Anton Paar units are out of my budget at this point. I have also been reluctant to purchase the unbranded refractometers over concerns of the very reasons you have shown in your video. I always intend to rely on hydrometers for OG and FG readings anyway but a refractometer will help with taking readings during the sparge. One quick question, were these readings taken with wort correction factor taken into account?

For the cheap model, is the reading from the SG scale? I have followed the advice to use the Brix reading and convert that to SG with a wort correction factor. I use the BeerSmith Mobile app tool for this. Using this method I have found my readings to be within a gravity point of my hydrometer readings. It is an additional step, lets me know on brew day how I am doing. It sounds like the Kegland one has a better SG scale built in. I use a hydrometer reading for my official OG and FG readings. Cheers!

Nice test. I suggest to additionally test this with a wort of higher gravity. An alternative could be to produce two sugar solutions of known gravity and test all devices against it (in your experiment, the SmartRef couldn't be incorrect). A few years back we tested standard homebrew hydrometers and cheap refractometers with two solutions of known (but secret) gravity - the solutions were distributed to several people, who tested with their personal device(s). The result was, that all devices were "good enough" for home brewing, however the refractometers seemed a bit more precise than classic hydrometers. The reason is probably because reading the measured value on a refractometer is less error prone than correctly reading a hydrometer (surface tension).

Most people probably understand that the cheap ones do not have the highest accuracy. But there is a methodology that can handle that problem very well and that gives good accuracy over the entire measurement range. If you make measurements with calibration fluid over the range you want to measure well. Then, with a small polynomial formula in a spreadsheet, you can get a value that is compensated for the inaccuracy. If it's worth the trouble, yes if you think that kind of thing is a bit funny, otherwise maybe not.

It would be great if Kegland considered venturing into the digital refractometer market. As you said in the video the current digital refractometer offerings mainly appeal the the very high end prosumer homebrewers. If Kegland or anyone else for that matter could bridge the gap between the Saber and something like the smartref they would be at a very competitive position for that sort of product.

Very interesting thank you for taking the time to share this information. For me, I'll wait until they can invent one that works post fermentation also. Cheers :)

Could you do the same test on a high gravity wort? It would be very interesting to see if the deviation stays the same or somehow scale with the gravity.

Hi David! Did you do any tests with higher gravity worts to know how much does the inaccuracy grows?

Interesting. Additional data points at 1.065 and 1.100 and maybe different SRM wort would be good to know. Would the kegland always off by .001 or by some linear range at 1.1?

I ferment liquid malt extract kits in a plastic bucket then transfer to a keg, my only monitoring capabilities are temperature and gravity. The other day I transferred a batch from a bucket into a carboy due to lack of space. Temperature was right, all looked correct. I then put the airlock in, but it was quiet. Panic stations the whole thing seemed to have died. Then I got my magnifying glass out and looked at the surface and there was little bubbles coming up to the surface. Today a lot of froth on the surface and it looks right, yet the airlock is still still. Gravity is reducing. What I'm thinking is that all the measuring devices have their place yet being able to look at what's going on and then with experience make a judgement on the situation is just as important. I'm sure this batch will be okay.

Another great video David. The difference in readings between the cheapest and more expensive is about 4 points. Other than having an affect on the final ABV, will an incorrect gravity reading of the wort have any affect on taste, colour etc? I find it very difficult to read an exact figure on the cheaper ATC as the display is very small, so I'm wondering if its worth the extra outlay?. Thanks, Ian

Thanks David. I may have to pick up a sabre

Regarding settings the Anton Paar device, which calculations do you use?

I use the blue box refractometer as a way to check when the mash is completed. When the brix stops increasing, i pull the grains.

I went back a few years ago and tested ALL of my brew store purchased brewing thermometers and found all but one off by at least 5 deg f. The worse was 11 deg off. Always test brewing instruments once a year!!!

I use a Milwaukee digital refrac and love it, but do find a lot of variation among readings even after just waiting a minute or two - even though it should correct for temperate.

ive calibrated my bluebox item to 1060 with my hydrometer, my PIL reads the same. This is where most of my SG starts so it works for me.

That's why I've always been lax about following recipes to the T... maybe it's cause I've only had one dissapointing batch.

No pictures just encase we have another 'hydrometer gate' scandal! J/K

“ Are you happy with the end result?”

Didn’t you just assume, that the most expensive was the most accurate? Why?

HI THERE I'M THE PICKY GUY! It's wert as in worst. not wort as in wart. bloody english...