Bob The Brewer Hi, I'm Bob and now I'm going to run through how to go about getting good hydrometer readings, and then I'll show you how to use them to calculate the ABV or alcohol by volume which is what you will find (in Britain) on the side of commercial bottles of beer, wine, spirits, etc.
 Well now, first we have to get a sample of your brew to test. There are several ways to do this, The most common is to syphon some of the liquor into a testing jar (looks like a large test tube). An easier method is to use a 'Wine Thief', if you have one. If using a 'thief' simply lower the thief into the liquor until the button on the bottom of the thief touches the bottom of the container, this will let the liquor flow inside through the hole in the bottom, then remove the thief from the container. You can now place the hydrometer directly into the top of the thief.
 Right, now we have to place the hydrometer into the sample jar. If you have a glass jar remember to slowly lower the hydrometer into the jar since a lot of hydrometer have been broken just hitting the bottom of the jar.Once the hydrometer is in the jar, hold the top between your thumb and finger and spin it in the jar, this should remove bubbles that are clinging to the side of the hydrometer.
In order to get a good reading you'll need to read the hydrometer from eye level. (Placing the testing jar on high surface can help with this.)

How to read the hydrometer depends on your particular model of hydrometer, most good hydrometers/lab instruments read from the lower meniscus, that is from the actual liquid surface and not from the top of the liquid that climes up the side of the jar and hydrometer. (There are some hydrometers that read from the upper meniscus, this will depend on you instrment, read the instructions to find out which).
 Now you've got your reading you need to write it down. It is best to record the whole number to three decimal places i.e. 1.050, the last decimal place is hard to read on a normal hydrometer so just do the best you can. This however is not your final reading, for accurate measurements you need to adjust for temperature. Most home hydrometers are calibrated for 20°C, Use a thermometer to get the exact temperature of the liquid and then use the temperature correction table that comes with the hydrometer to work out the real reading. (the correction will be about -0.001 for -4°C, and +0.001 for +4°C above or below 20°). Your result can now be called the Specific Gravity (SG).
 To calculate the alcohol level in a liquid with a hydrometer you will need two readings. The Original Gravity (OG), that is the specific gravity of the liquid before any yeast is added, (and no, there is no way of calculating this after the liquor has fermented) And the Finial Gravity (FG), that is the specific gravity of liquid after all fermentation is complete.
 Now you have all the readings corrected for temperature and the works all we have to do is run Alco-Calc, press the Alco-Calc button then just enter your OG & FG into the form and press return and stonehelm.co.uk will do the calculation for you, what can be easier than that? Well that's all folks, I hope you understand how to use a hydrometer and how to calculate the ABV of your beer, wines, and liqueurs. Run Alco-Calc