Free Joy of Home Wine Making by Terry A. Garey

to test into a glass or wide plastic test tube, but not one that is so wide that you waste a lot of wine. You can buy these at a wine supply store.
    Gently drop the hydrometer into the liquid, giving the hydrometer a quick spin as it enters the liquid to get rid of air bubbles.
    It will float in the liquid.
    Now, if the liquid is plain water, the hydrometer will float at a specific height on the scale, which would be 1000 specific gravity, or 0 percent potential alcohol. If there is sugar in the water, the water will be thicker, and the hydrometer will tell you how much is in there. This is called measuring the Specific Gravity, or SG, in the must or wine.
    Allowing for temperature fluctuations (the ideal temperature of the liquid would be 60°F or 15°C) and tiny specks of fruit suspended in the juice (you sort of have to wing it, there) you can learn how much sugar is present in the liquid, and therefore how much potential alcohol there is.
    This is really useful, because you can add either more water or more sugar to your must, depending on the need. This way you avoid a wine too weak in alcohol to keep well (under 10 percent or so) and avoid having too much sugar in the wine, since the yeast can handle only 14 percent potential alcohol at best. If the reading says you’ve got 18 percent potential alcohol in there, you are going to have a very, very sweet wine if you don’t thin it out.
    If you take a reading before you add the yeast, and REMEMBER TO WRITE IT DOWN, and measure the wine at the end of fermentation, you will know how much alcohol is in the wine. Nifty, huh?
    If you didn’t take a reading at the beginning of the process, the hydrometer cannot tell you how much alcohol is in a wine. It’s sad, but true. To do that you have to have a fancy, expensive gadget, which only the pros or serious (or rich) amateurs bother with.

    The hydrometer also helps you keep track of the fermentation and offers a better way to know when it is done. When a recipe says, “Rack into a secondary fermenter until fermented out,” you’ll know, with the help of the hydrometer, when the sugar has fermented out and you have a dry wine.
    It’s best to buy a hydrometer at the wine supply store. If you make beer, you might already have one, but it might not have the range you need for winemaking. Take a look. You want one that measures the specific gravity from .990 to at least 1.160 and that also has a scale for potential alcohol from “blank” to 21 percent or 22 percent. Some also come with the added attraction of the Balling scale, which used to be standard in American home winemaking but is no longer. There’s nothing wrong with it, I just don’t feel the need for three different readings! If you are comfortable with the Balling scale, use it.
    Why do you need to see readings of .990 and blank, if water is 1.000 or 0 percent? Temperature fluctuation and specks of fruit, that’s why. All is not crisp and clean in science.
    Place the tube on an even surface. (You can test this with a marble or ball bearing. If it rolls, the surface isn’t even.) Put in the hydrometer and spin it a little to get rid of the air bubbles. Squat down and get your eyes even with the level of liquid, and see where the level is. Water tension makes the liquid bunch up a bit right up against the sides of the hydrometer, so the correct level is away from the edge, but not at the sides of the hydrometer.
    Here’s a sample of readings from a hydrometer:
     
S PECIFIC G RAVITY
P OTENTIAL A LCOHOL
0.990
blank
1.000
0
1.005
1.010
0.9
1.015
1.6
1.020
2.3
1.025
3.0
1.030
3.7
1.035
4.4
1.040
5.1
1.045
5.8
1.050
6.5
1.055
7.2
1.060
7.8
1.065
8.6
1.070
9.2
1.075
10.4
1.080
11.2
1.085
11.9
1.090
12.6
1.095
13.4
1.100
14.0
1.105
14.9
1.110
15
1.115
16.4
     
    Fear not if you feel lost. All will become clear if you look at the hydrometer and play with it in some fruit juice and water. (It’s your toy; you can play with it.)
    In reality, there are more increments on