I recently was notified of a great special that More Beer was running for a short time for their dual-scale brewing refractometer. I had been wanting one of these homebrewing instruments since I began home beer brewing in 2004. The special price at which it was marked made me jump at the deal and now I have one in my arsenal of testing tools.
I have always had trouble reading the brewing hydrometers that I have had as they never really floated evenly in the testing tube. They always cant to one side or I have to spin them continually to remove bubbles so I can try to get a good reading. They also require quite a bit more wort and it can be difficult to collect liquid during a vigorous boil in order to try to reach the proper target gravity for a recipe.
A refractometer always seemed like a much better solution. They only require a drop or two of liquid to test. Temperature is not really a concern because the very small volume of liquid quickly reaches the temperature of the device within seconds. The ATC (automatic temperature compensation) feature of this particular refractometer means it can work in an environment between 50-86 degrees Fahrenheit (10-30 Celsius) instead of the 68 degree Fahrenheit calibration used by most refractometer makers. The More Beer Dual-Scale Refractometer with ATC also has a non-linear Specific Gravity scale built into the device so a brewer can directly read correct Specific Gravities without worrying about accuracy.
One thing of which I was not aware concerning the workings of a brewing refractometer, however, was that the presence of alcohol in a sample causes an incorrect reading on the device. This means that once fermentation has begun or has finished, additional calculations will be required in order to arrive at the correct Specific Gravity of the beer sample. I have seen several spreadsheets available online to help with the conversions though. More Beer has one here. Northern Brewer has an online calculator here. I also decided to write my own version which can be found here. The formulas I utilized come from PrimeTab and RealBeer.
Overall, I am very happy with this purchase and I expect to enjoy using it for years to come.