As a homebrew beginner, you’ll most likely start off using a hydrometer to measure the specific gravity of your beer. This involves pulling off about half a pint of beer, throwing it in the testing tube, dropping the hydrometer in and reading the results.
I don’t know about you, but especially as a beginner I worried about my beer A LOT. I found myself wanting to check and re-check the progress of the fermentation every couple of days. What occurred to me after the first couple of batches was that I was “wasting” a lot of beer (Oh the horror!).
This wasn’t necessarily true, wasting implies that it was just being tipped down the sink; on the contrary, it’s very important to taste and test your beer as you go. It will give you a better handle on what the yeasties do at what time in the fermentation, and give you a chance to identify any problems early on!
However, it still bothered me. I ran a search on my concern, and came up with a couple of threads online about refractometers. Refractometers are instruments that measure the bending of light (refraction) through a liquid; the more sugar present, the more the light bends. Across the beverage industry they are used to measure the density of the sugars in the solution, or specific gravity; which is what we homebrewers usually use a hydrometer for.
The best thing about a refractometer is that it only takes a couple of drops of wort to get a reading! Crazy right?!
You will get a reading in Brix, and to convert this to our regular specific gravity readings you simply multiply by 4; e.g. 15 Brix = 1.060 SG. Here’s the conversion calculator.
The other thing I love about a refractometer is that you can take a reading while you’re still boiling, to see how close you are to your target gravity; no more kicking yourself once it’s in the carboy beacause your efficiency was off! (or did that only ever happen to me?)
The only tricky thing with a refractometer is that on its own it can’t give you a final gravity. You need to use a formula to calculate what the difference in Brix readings means in terms of FG.
Did I mention that I’m a lazy homebrewer? Well, I am; no fancy algebra for me on brewday! There are calculator tools out there online that will do all the translation for you, my favorite is over at More Beer. It will do all the hard work, and you can stop wasting your precious liquid gold.