Hydrometers Vs Refractometers
Any brewer worth his wort understands that measuring gravity often, is key to producing consistently high quality beer. Measuring gravity properly will help a brewer do several things:
- Measure mash efficiency.
- Gauge whether you are hitting the targets set for your recipe.
- Help understand the balance of your beer and how it can be improved if necessary.
- Measure the progress of fermentation.
- Know with certainty when fermentation has stopped or is finished.
- Calculate the alcohol content of your brew.
The most basic tool for measuring specific gravity of wort is the Hydrometer. A hydrometerfunctions by displacing liquid based on its own density and measuring the amount of liquid it displaces. For instance, a specific gravity of 1.000 indicates the liquid has the same density as pure water. A specific gravity of 1.050 is denser than water by 5%, and a specific gravity of 0.950 would be less dense than water by 5%. Hydrometers are probably the most basic and least expensive tool for measuring the specific gravity of a liquid, but they do have several drawbacks:
Require Adjustments Based on Temperature:
Variations in the temperature of the liquid require an adjustment to the results. The warmer the liquid, the less dense it will be, affecting your assumptions about sugar content
Require Large Sample Sizes:
To measure, a brewer will usually pull a sample of beer from the fermenter into a graduated cylinder and then discard the sample to prevent contamination. If you measure your gravity several times over the life of your beer, which is good practice, this will waste several beers’ worth of wort as it ferments. I think we can all agree that this is a bad thing.
Risks Batch Contamination:
Opening a fermenter to take a sample means increasing the risk of contamination. Some brewers will simply set their hydrometer in their fermenting wort when they take a measurement, thereby increasing the risk of contaminating the whole batch. Unfortunately, you cannot measure the density without putting a foreign object into your fermenting wort, but you can lower the risk significantly by properly sanitizing and using the right equipment for taking a sample.
To correctly take a sample from a fermenter, you need a beer thief. In order to measure the results, you need a graduated cylinder. You also need to take the temperature of the wort, so you have to have a thermometer (which you probably already own). The point is that you can’t just have a hydrometer; you also have to have ancillary equipment.
Overall, the hydrometer is a worthwhile investment, and will help you make better beer by measuring your results for repeatability.
Another tool for measuring is the Refractometer. The refractometer does not work by measuring the density of the liquid; it works by measuring the refraction of light through the liquid and calculating the content based on that measurement. There are several advantages to using a refractometer instead of a hydrometer.
Uses Smaller Sample Sizes:
Unlike the hydrometer, the sample size for the refractometer is only a few drops of wort, meaning you can leave more in the fermenter for packaging.
Temperature is less of an Issue:
A small sample size means it will cool faster. In addition, many refractometers have temperature correction features which will allow for small differences in temperature without inaccuracies.
Requires Less Equipment
No need for a big, bulky beer thief, a graduated cylinder or a sanitized thermometer. You can simply sanitize a dropper or a pipette and pull a very small sample.
You Don’t Open the Fermenter Much
To get a beer thief into a fermenter, you have to take the entire top off your fermenter. To take a measurement with a pipette, simply pull out the airlock, dip the sanitized pipette, and replace the airlock. By reducing the size of the entry point and time of exposure to open air, you minimize the risk of contamination during sampling.
Because you are able to lower the risk, you can sample more often during fermentation. This can help build a profile of your typical fermentation process and identity problems early on. Because temperature is less of an issue and the sample size reading is smaller, the refractometer allows you to quickly take samples more often during the brew process.
For any brewer, a hydrometer can be a valuable tool. For beginning brewers who want to budget their brewing equipment expenses, the purchase of a hydrometer can be easy to justify over the expense of a refractometer.
If you are an intermediate or advanced home brewer, however, the additional one-time expense of the refractometer is well worth the money and will pay dividends in better consistency of your brewing process and the additional convenience of easier and smaller sampling.