Brewing Gadgets: Refractometer

A hydrometer is a must have for brewers and wine makers to measure the amount of sugar available for conversion to alcohol, and to estimate the amount of alcohol converted during and post-fermentation, and to know when fermentation is complete.

As handy as they are, there are some real downsides to the hydrometer. Most notably, it can take half of a pint of wort or juice in order to float the hydrometer for a reading. This risks contamination of your beer or wine unless you dispose of the test liquid (which means less to drink later).

Another downside is that hydrometers are calibrated for testing liquid at 70°F.  If the liquid is hotter or colder calculations are required to correct the reading due to fluid dynamics or something like it that I should have paid more attention to in physics class.

Enter the Refractometer, a device that looks like the handle of a light saber and uses the variance in light refraction through the liquid to measure its density which can be calibrated to measure the amount of sugar and/or alcohol present using only a small drop (which cools to room temperature while measuring).

I was intrigued by the simplicity of a refractometer, so I broke down and bought on on eBay for about $30, or 5x the cost of a hydrometer.  Overall, I am quite happy with my purchase and the convenience, however don't plan on throwing away your hydrometer just yet.  The refractometer works amazingly well for testing the gravity during the brewing process while liquids are hot and the readings are very accurate when compared to a hydrometer.  However, after fermentation has begun, the alcohol content begins to skew the readings so I still take most final gravity readings with a hydrometer.

I think you could calibrate a refractometer specifically to measure alcohol content to compensate (mine even has a separate scale just for that) but I'm just to lazy for that.  Here are examples of both methods of measurement using the same wort.  It should be noted that while I let the wort cool for the hydrometer reading it was still about 80°F when taking the reading so its reading is a tick low due to the higher viscosity at that temperature.  Refractometer readings are in Brix % (which seem very close to °plato I see in pro recipes) so you need to convert them to specific gravity for comparison with a hydrometer.  I found this table on the Internet that makes the conversion easy.

The refractometer also allows quick readings during the mash process to check to see how the conversion process is going.

I highly recommend adding one to your brew kit if you are trying to better understand the efficiency of your brewing process, but just don't expect to get rid of your faithful hydrometer.

Would be a great Christmas gift too!

-D

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