Refractometer vs Hydrometer: Which Should You Use?

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In this post, we are going to compare refractometers vs hydrometers, both of which are two very important tools in the brewer’s arsenal when it comes to dialing in the brewing process and making quality beer.

The difference between an ok beer and great beer in many cases comes down to the brewer’s dedication to always looking for ways to improve upon his brewing skills. Measuring the specific gravity of your beer is one of the simplest and most important things you can do during the brewing process in order to evaluate how your brew day went and pinpoint areas that you can improve upon in order to dial in your processes and improve upon the quality of the beer you make.

When you are making beer, taking specific gravity readings allows you to measure the amount of sugar in the wort or beer as compared to water which has none.

For example, if you took a specific gravity reading of pure water it would read 1.000. If you took a reading of a liquid that contained some sugar in this case beer, and for the sake of simplicity for this example the reading comes in at 1.050, which means this liquid is 5% more dense than pure water.

A refractometer and a hydrometer are the tools used to take these measurements and will allow a brewer to:

  • Determine if you are hitting the gravity targets for the recipe they are brewing
  • Calculate the efficiency of the mash
  • Take readings during fermentation to watch its progress and determine when it has finished.
  • Calculate the ABV or alcohol percentage of your beer

Refractometer vs Hydrometer  A refractometer next to a hydrometer in front of pints of beer next to the words refractometer vs hydrometer.

It is not uncommon for novice brewers to mistakenly believe that a hydrometer and a refractometer are similar tools that do the same thing. Although they do provide the same measurements in the end the way they go about it is different.

A hydrometer measures the actual density or specific gravity of the liquid whereas the refractometer uses light to take a measurement of how much sugar is in the liquid you are measuring.

Neither one is superior to the other, they both have advantages and disadvantages and it really comes down to the brewer’s preference on which they prefer to use. We will now take a more in-depth look at both of these tools, how they work, and the advantages of each…

Hydrometer

The most well-known of the two, the hydrometer measures the specific gravity of your wort and beer. This is accomplished by placing it directly into the liquid, which allows you to take a measurement of the amount of liquid it displaces as a result of its density.

A hydrometer has a wide bottom and a much slender top. It is typically made out of glass but not always. The bottom is weighted down in order to keep it upright when it is placed into the liquid. The upper slender end has a scale or measurements printed on the side of it. You simply place the hydrometer into the liquid and it floats while displacing the liquid.

It will float higher or lower depending on the Specific Gravity of the liquid. You take your reading where the liquid meets the scale on the side of the hydrometer.

A hydrometer is a simple and inexpensive tool that does the job effectively and is truly all you need to dial in your gravity readings. However, like all tools, it does have some drawbacks that you should be aware of.

A Loss of Beer

Compared to a refractometer using a hydrometer requires larger sample sizes of the wort or beer to be pulled from the fermenter. Every time you take a reading with the hydrometer you need to fill up the cylinder with the liquid.

It is not recommended that you return the liquid back into the fermenter as you can risk contaminating your beer causing off-flavors or infections. As a result, you need to dispose of it each time, which depending on how many readings you take can result in a fair amount of wastage.

Temperature Requirements of Sample

Hydrometers require that the liquid you are taking a measurement reading of is at a certain temperature. Typically you can get a fairly accurate reading if the liquid is at room temperature, however, the warmer a liquid is the less dense it will be which if too warm can give you an incorrect reading. Each hydrometer will come with instructions that provide you with the ideal temperature range for the sample reading.

Additional Equipment Required

Although the additional equipment you require to use a hydrometer is not costly it is worth mentioning. A beer thief is basically a siphon of sorts that allows you to take samples of your beer to test it. You also will require the graduated cylinder which you fill with the sample you took using the thief, most hydrometers do come with the cylinder. Lastly, you will need a thermometer in order to ensure the sample is at the right temperature before taking the reading.

Concerns Over Contamination

One of the concerns of constantly taking hydrometer measurements during fermentation is the added risk of contamination. Anytime you open the lid on your fermenter you are taking the risk of contaminating your wort.

Exposing the wort to the object you are using to remove the wort from the fermenter poses the same risk. Whether it is the graduated cylinder that comes with the hydrometer, a measuring cup, or a siphon, regardless of how well you believe you have sanitized them, exposing them to your fermenting wort does pose risks.

We have even heard tell of some brewers placing the hydrometer itself into the fermenting wort instead of removing a sample of it. Doing so poses the same risks of contamination and potentially more as it is very likely you will leave the lid off the fermenter even longer by taking measurements in this manner.

A hydrometer is a very simple but worthwhile tool that will help you consistently make better beer. This post will provide you with further details on how to use and read a hydrometer.

Next, we will take a look at what a refractometer is and how it works…

Refractometer

The big difference between a refractometer vs a hydrometer is it does not measure the density of the liquid, it instead measures the dissolved sugar content in the wort or beer by measuring how the light refracts through it.

Unlike the hydrometer you do not place it in the liquid, instead, it resembles a spyglass or telescope used by pirates, you hold it up to your eye and aim it at a light source, and you will see a measurement within it that is displayed in Brix. In order to convert Brix to specific gravity, you will need to use a calculator, brewers friend has one you can easily use.

Sample Size

If you are concerned about the amount of beer you are wasting when taking readings with a hydrometer, you will be pleased to find out that this is not an issue when you use a refractometer as the sample size required is only a couple of drops.

Temperature Not a Concern

Because the sample size required is so small you do not have to worry about the temperature as much as a drop that small will come into the correct temperature range so quickly that it is not an issue. If you are concerned about the temperature being too hot, most refractometers you purchase have a feature that adjusts for temperature corrections.

Less Chance of Contamination

Because you are taking such a small sample size there is no need to remove the whole lid from the fermenter or use a siphon to extract the sample. Refractometers come with a small pipette that you use to draw the sample with. In order to draw the sample and reduce the potential exposure to oxygen and containments simply remove the airlock and draw the sample through the smaller opening.

No Additional Equipment

Unlike the hydrometer where you need a few additional pieces of equipment, the refractometer does not need any.

More Expensive

One of the drawbacks of the refractometer is that it comes at a higher price point than its counterpart, you can find them costing anywhere from $35 – $100 depending on the quality of the unit. Although not an overly costly piece of equipment, it is certainly higher than a hydrometer which typically sells for between $15 and $20.

Loss of Precision

A refractometer is an excellent tool for measuring your specific gravity (Brix) before and after your boil. However, during fermentation the measurement it takes can lose some of its precision, this is due to the yeast consuming the sugars and converting them into alcohol which impacts the way the light is refracted. However similar to converting Brix to Specific Gravity there are online calculators that can help you correct the measurement.

The Final Word

In the end, when it comes to the refractometer vs hydrometer they are both excellent tools to help you improve and dial in your beer-making skills. Most brewers start out with the hydrometer and then purchase a refractometer later. However neither one is truly better than the other, each has benefits and negatives that the other does not. We know of professional brewers that use hydrometers and others that use refractometers and some that use both in conjunction, it really comes down to you and which you prefer using, both will do the job well if used properly.

P.S. Be sure to grab the recipes for my top 5 beers from my brewpub, details are on the side of the blog or at the bottom if you are on your smart device.  Cheers!

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