Product Review | Hanna Instruments Digital Refractometer for Brewing

Author: Marshall Schott

For some, brewing is all about stripping the process down without worrying about the finer details. A handful of this, a sprinkle of that, voila, beer! As much as I appreciate this mentality, I definitely cannot relate, as I’m a nut for precision when it comes to making beer and I get my kicks off of knowing I hit certain target numbers. As any brewer is very well aware, there are a lot these target numbers in brewing, all of which rely on specific instruments for measurement. One of the measurements focused on most in brewing has to do with the amount of sugar present in solution, as it provides information to the brewer about mash efficiency and ultimately allows us to determine the strength of a beer. There are a few different scales used by brewers to measure this sugar content, which can understandably cause a bit of confusion, hence this very brief attempt at an explanation.

The most popular scale used by homebrewers is specific gravity (SG), which is the ratio of the density of a substance (wort/beer) to the density of a reference substance (water). The tool used to make such measurements is the hydrometer, a science-y looking device included in most homebrew starter kits. More commonly used by professional brewers, the degrees Plato (°P) scale represents the sugar content of a solution as percentage by mass, which is basically the same as the degrees Brix (°Bx) scale often used by winemakers. While Plato and Brix are ever so slightly different, it’s so small that many accept them as being largely interchangeable. The tool generally used to measure °P and °Bx is the refractomer, a device that relies on the index of refraction to determine the sugar content of a solution.

I’ve gone through my fair share of hydrometers over the years, as they don’t seem to hold up too well to being dropped on concrete garage floors. Desiring a less breakable option that was more precise and didn’t require such a large volume of wort for measurement, I picked up my first handheld refractometer a few years ago. What I appreciate most about these types of refractometers is how quick they provide readings and how small of a wort/beer sample they require. However, it’s been my experience that the blue coloring in the daylight plate fades with time, making it difficult if not impossible to get an accurate reading. I’ve had to toss 2 refractometers so far because of this. Also, as much as it may not really matter, the closeness of the hash marks hinders the ability to get truly precise measurements. For that, one would require a device with a bit more oomph.

A representative from Hanna Instruments recently reached out to chat about various products they manufacture for use in brewing, one of which is a digital refractometer. Given the nature of what we do here at Brülosophy, this device seemed liked a legit way to ensure the most accurate readings possible, so when asked to put one through its paces and provide an honest review, I accepted!

The product reviewed for this article was provided by the manufacturer in exchange for an honest review; no other compensation was provided. The opinions expressed in the article are solely those of the author and a concerted effort was made to approach the review from an unbiased perspective.

Since this isn’t a technical paper covering exactly how refractometers work, I’ll focus my review on the stuff that matters to most brewers. Real quick, there’s a really simple method for converting SG to °P and vice versa that’s surprisingly accurate:

°P = last 2 digits of SG/4

SG = °P x 4

So a reading of, say, 12 °P on the digital refractometer would equate about 1.048 SG. I prefer to use a calculator for accuracy’s sake, personally, but as a rudimentary method, this works pretty well.

Build Quality

The unit arrived in a well packed box containing the digital refractometer, batteries, a pipette, a small piece of microfiber cloth, and an instruction pamphlet.

Immediately upon removing the refractometer from the box, it was apparent by the weight and feel how durable it was. The water resistant ABS plastic housing feels sturdy enough to withstand the bumps bound to happen in any brewery while the sample well is made of stainless steel, which is both strong and very easy to clean.

The functions on the refractometer are simple and generally self-explanatory, just 3 buttons for powering it on/off, calibration, and taking the reading.

Calibration

After spending all of 30 seconds installing the battery, I read through the fairly brief instruction pamphlet and noticed they recommend calibrating the unit with distilled water prior to every use. Out of curiosity, I decided to take a reading of the water without calibrating first and found the refractometer was already spot on.

I then went through the very simple calibration process just because the instructions said I should before moving into a comparison of different devices.

Accuracy

Since I wasn’t brewing when the refractometer arrived, I did an initial accuracy test using store-bought apple juice, which I’ve learned through cider making is usually between 1.048 – 1.054 SG, or 12.4 – 13.3 °P. After ensuring my hydrometer and handheld refractometer were calibrated, I measured the juice with each.

Interestingly, while my calibrated handheld refractometer showed the exact same ˚P as the digital refractometer, the SG was 0.003 points shy of the calculated conversion to 1.053 SG. Because I’ve only ever paid attention to the SG reading from my handheld refractometer, I’m only now realizing my slightly lower than expected brewhouse efficiency may not actually be lower. Huh.

Automatic Temperature Compensation (ATC)

A lot of handheld refractometers are advertised as having ATC, or automatic temperature compensation, which really just amounts to the daylight plate cooling the sample somewhat quickly given it’s just a couple drops. Nothing about it is really “automatic” and I’ve found waiting about 45 seconds after adding the sample to the plate results in more accurate readings. While the Hanna digital refractometer actually compensates for the temperature of the liquid in the well, I found this not to be much of an issue since the few drops of liquid used usually stabilize at ambient temperature within a few seconds anyway. I attempted to test this out on brew day by measuring 3 samples of the same wort at different temperatures, but it proved difficult, likely due to the starting temperature of the stainless sample well. Regardless, in each case, immediate readings of the 3 samples were identical and all 3 stabilized at the same ambient temperature within 30 seconds. It should also be noted the temperature can be displayed in either Celsius or Fahrenheit.

Speed

Hanna claims the digital refractometer takes approximately 1.5 seconds to display readings, a claim I thought best to test out.

I initially intended to record my phone’s timer next to the refractometer, but that proved difficult because I was using my phone to record… yeah. Anyway, readings are displayed basically immediately.

Ease of Use

Using the Hanna digital refractometer is easy. Very, very easy. Just turn the unit on, drop a sample in the well, then press the “read” button. Since refraction is a function of light, brighter environments can skew readings a bit, so Hanna recommends covering the sample during measurement if this is the case.

My garage doesn’t receive any direct sunlight and isn’t generally very bright, so this isn’t an issue for me.

Cleaning

Hanna is very clear about the sensitivity of the prism in the sample well and recommends being careful not to scratch it when cleaning. They even include a cute baby shammy cloth with the refractometer.

My cleaning process takes less than a minute and consists of first dabbing some paper towel in the sample to absorb as much as possible without touching the prism. Next, I drop distilled water in the sample well, dab it up with some dry paper towel, then very gently wipe the well down with the shammy until dry.

Storage

My biggest concern when I considered storing the digital refractometer was dust and other small particles in the air potentially landing on and scratching the prism. Rather than taking it in and out of a box with every use, I store the unit toward the back of my workbench, under a shelf, with the small towel covering the sample well.

When time to use, I simply pull the unit a few inches away from the wall, far enough from the ledge that my clumsy ass can’t bump it off, and proceed to take the measurement. Piece of cake.

Measuring Finishing Gravity

If I had a kernel of grain for every time I read a forum post or email about an under-attenuated beer based on a refractometer measurement taken post-fermentation…

Refractometers rely on the index of refraction to measure the sugar content of a solution, and refraction is influenced by alcohol such that readings taken of alcoholic solutions (like beer) will be inaccurately higher than reality. Hanna provides the following explanation:

It should be noted that once fermentation begins, ethanol and the residual sugar interfere with each other and prevent an accurate reading of the Brix value of your residual sugar. For this reason, this refractometer cannot be used with finished beer or other fermented beverages. It is designed for use with wort only.

Thankfully, some people far smarter than me have worked out a way to correct for this and made snazzy calculators to simplify the process for folks like me. To test it out, I measured the gravity of a beer that had recently finished fermenting with both the digital refractometer and my FG hydrometer.

A reading of 6.1 ˚P equates to 1.024 SG and would suggest either incomplete or stalled fermentation, though the hydrometer measurements proves this isn’t the case. Using an online calculator that applies the wort correction factor and accounts for starting gravity, we get a clearer picture of the actual gravity of the fermented beer– the 6.1 ˚P is converted to 3.1 ˚P, or 1.012 SG. Precisely what my finishing SG hydrometer showed.

I don’t mind taking hydrometer samples to measure FG because it gives me an opportunity to taste the beer, but I absolutely love the idea of being able to steal a few drops as a way of checking fermentation progress.

| THE VERDICT |

Indeed, the Hanna digital refractometer costs more than commonly used handheld refractometers and hydrometers, and no, it’s not necessary for the production of good beer. I get it. Would I recommend everyone go out and buy one immediately? Of course not, but neither would I recommend people not buy one. That’s up to each brewer to decide for themselves. While the unit may be cost prohibitive for some, that doesn’t change the fact that it is solidly built, incredibly easy to use, and remarkably accurate. For those who care about this stuff and brew frequently enough, the Hanna digital refractometer may very well be a worthy purchase.

With as often as I brew, and especially given the experimental nature of my brewing, I’d been eyeing digital refractometers for a few months prior to receiving the Hanna for review. Most of what I found was comparable in price if not slightly more expensive, and the cheaper options didn’t offer the features I desired such as measuring in degrees Plato. The Hanna certainly fit my preferences closest, and while I think it’d be rad if it allowed users to switch between different measurement scales, I understand why this is difficult and don’t mind using a free online calculator for conversions. The only other downside I can think of is that it runs off of batteries that will eventually require replacement. For as little time as the unit is actually on when taking readings, I’ve a hunch the battery life is going to be quite high, but it’d be nice to avoid this all together by being able to plug it in.

Overall, my experience using the Hanna digital refractometer has been very positive and I’ve little doubt those interested in such a device would agree it’s a high quality machine that offers another level of convenience to the brew day. The Hanna Instruments HI96841 Digital Refractometer for Brewing is currently only available direct from Hanna’s website.

If you have any questions or thoughts about this product, please leave them in the comments section below.

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