Can A Refractometer Measure Alcohol? (Measure Alcohol With A Refractometer)

When you’re making your very one beer or wine at home, you’re bound to wonder just how much alcohol you have made in your final bottles.

Can A Refractometer Measure Alcohol

But, I’m pleased to report that you don’t have to just wonder or guess. There are different ways of working out just how much alcohol you’ve produced per unit volume.

And by doing so, it’s much easier to judge when to stop drinking, because you’ll have a much better idea of when you’ve reached your preferred limit.

We all know how easy it is to just keep on drinking something you love the taste of if you’re not wary about how much alcohol is in there.

In one of our other articles, titled “How To Measure Alcohol Content With A Hydrometer” I explain exactly that.

You can access that article on this link. But that’s not your only option – you can also measure your alcohol content using a refractometer, and in this article, I’m going to explain everything you need to know to do so.

I’m also going to cover what exactly a refractometer is, how it works, what type you’ll need for your home brew.

Please feel free to scroll ahead to any section that jumps out at you. Here goes!

What Exactly Is A Refractometer?

A refractometer, also known as a Brix meter or a saccharometer, is basically a tool used to measure the concentration of a substance in a water-based solution.

It’s a small device featuring a prism mounted in an aluminum body, complete with an eyepiece and a Brix scale.

It turns out that refractometers are frequently used in the manufacture of food and drinks. They come in particularly handy when calculating the concentrations of things such as fruit juices, alcohol, and vegetable oils and such.

However, it’s worth noting that while there are some refractometers out there that can measure the level of alcohol in water (% ABV) directly, they cannot be used to measure the alcohol content of beer.

The types of refractometers that homebrewers use work by measuring the sugar concentration present in the liquid, and using that value you can work out the level of alcohol that’s there.

So as you can imagine, the sugar present in beers can really mess up the reading.

The Brix scale on the refractometer is basically a measure of the number of grams of sucrose sugar present per 100 grams of liquid, measured on a scale of one to 100.

How Does A Refractometer Work?

You may remember learning about refraction in your school days, and how light can change direction as it moves from one transparent material, such as air, to another transparent substance, such as a lens or a glass of water.

The amount of light refracted by a substance depends on the nature of the substance it’s passing through, and what is known as the refractive index of that substance.

The more sugar that’s present in a water-based mixture the greater the refractive index of the mixture becomes, so the higher the concentration of sugar, the greater the angle is refracted.

Without any liquid on the prism part of the refractor, the scale is a pale gray-blue color.

But when a water-based solution touches the prism, the light passing through the prism of the refractor bends, and this causes the initial part of the scale to turn white.

The refractometer should be set up such that when pure water touches the prism, the borderline between where the white and blue areas meet on the scale is at exactly zero Brix.

The Brix scale is basically a measure of the percentage of sugar that’s dissolved in the water mixture.

Best Type Of Refractometer For Home Brewing?

The good news is that there are refractometers that are specially designed for home brewing. In addition to their Brix scale, they also have a second scale which measures specific gravity.

And these refractometers usually feature automatic compensation for temperatures, so you don’t have to wait around for your wort mixture to cool down before you use it.

The refractor that I recommend for home brewing can be found on this link.

Not only can you use it to automatically adjust it for temperature compensation, but it also features a focus adjustment ring on the eyepiece, and it comes with its own dropper.

How To Measure Alcohol With A Refractometer

In order to measure the alcohol in your home brew with a refractometer, you need to take two different readings.

As mentioned earlier, the job of the refractometer is to measure how much sugar is dissolved in wort.

And since the fermentation process requires that the yeast convert the sugar in the mixture to alcohol, there will be less sugar after fermentation than before, and the difference between the refractometer readings before and after fermentation can be used to work out the ABV % of the finished brew.

I’ll be going through the various calculations you need a little later, so keep reading or scroll ahead.

Your Step-By-Step Guide To Taking A Refractometer Reading

Can A Refractometer Measure Alcohol

This easy to follow step-by-step guide will walk you through how to take your refractometer readings. Here goes!

Step One: Use Distilled Water To Calibrate The Refractometer

Although your refractometer would have been calibrated while it was still in its factory, I would strongly recommend that you check up on the calibration every time you use it.

Because why bother measuring the alcohol content at all unless you want as accurate a figure as possible?

But don’t worry, it’s easy. You open the flap covering the prism, and place 2-3 drops of the water on it. Close, and then hold the instrument up to the light.

Using the focusing ring, adjust the instrument until the Brix scale, which will be illuminated in blue and white, is crystal clear.

And remember to replace the cap before carrying out the next step.

Step Two: Dry Out The Refractometer

Then you need to use a soft cloth to carefully wipe dry the refractometer’s prism.

This is vital, because if there were any water left on the prism next time you test a sample of wort, this will have an effect on the measurement and give you a false reading.

Step Three: Take A Small Sample Of Your Wort

To take your sample you’re going to need a wine thief, metal spoon or pipette.

But before you take your sample, please ensure that whatever you decide to use has been thoroughly sanitized first, to ensure that you don’t ruin your batch by introducing bacteria or any other nasties.

You only need 1 to 3 drops of wort as your sample.

Step Four: Place Your Drops Of Wort On The Prism

Open the plastic flap over the prism, and add your drops. Then seal the flap, and ensure that your sample is evenly spread across the prism.

Step Five: Hold The Refractometer Up To The Light And Observe The Reading

Grab the refractometer and hold it up to a light source, looking through the eyepiece, adjusting the focusing dial as necessary. Examine where the white section meets the blue to get your Brix reading.

Step Six: Clean And Dry The Refractometer After Every Use

Don’t forget to clean the refractometer after every use. You need to clean and dry it, removing every last trace of wort before returning the instrument to its case.

The Refractometer Calculations That Give You The Alcohol By Volume Percentage Of Your Home Brew


Automatic Temperature Correction

When you take the first reading, before the yeast is pitched in the wort, and it’s still unfermented, the refractometer reading is very accurate.

But once the fermentation has begun, the alcohol can throw out the readings a little, which means that the Brix reading has to be adjusted accordingly.

The good news, however, luckily, is that most refractometers for home brews feature automatic temperature compensation.

But, if yours does not, then you can use a simple mathematical formula that will take the temperature issue into account, and give you a more accurate result…

For this, you will also need to measure the specific gravity with your refractometer, and you then pull the readings into the following equation:

Corrected Brix reading = (SG – 1)/0.004

where SG represents the specific gravity reading.

(There’s also a wort correction factor to take into consideration – but we’ll get into that shortly.)

Easy Formula For Calculating The ABV (%)

You can use this temperature corrected Brix reading to then calculate an approximate value of potential alcohol content, by applying it to the following mathematical formula:

ABV (%) = Corrected Brix reading x 0.59

As you can see, it’s super simple, and you don’t need any sort of special online calculator , and you can just use the calculator app on your smartphone.

The above formula for ABV does not take into account the wort correction factor, but to be honest this has a very minimal effect on your calculation, so if you don’t need the ABV to be really precise, you can just make do with this formula.

Wort Correction Factor

Now, technically what a refractor measures is the percent value of sucrose in a water-based solution. But, wort features several different types of sugars in addition to sucrose.

There’s a lot of glucose and also some fructose, maltose, and of course sucrose.

These other sugars have a marginally different refractive index than sucrose alone, bending the light to a slightly different angle. Which means that you may not get an entirely accurate reading.

For most refractometers, all you have to do to correct the reading is to multiply it by a wort correction of 1.004.

Take Several Measurements

Since taking readings requires so few drops in the way of samples, there’s no reason why you can’t take several sample readings of your home brew.

This way you can take averages of your readings to get the most precise values that you can.

Final Thoughts

So, as you can see, using a refractometer to calculate the alcohol in your home brew is relatively simple and straightforward, with just a handful of quick calculations.

What’s more, you don’t have to sacrifice as much of your mixture for your sampling if you’re using a refractometer rather than a hydrometer.

Brew and drink responsibly!

Andrew Carr
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