THE HYDROMETER

The hydrometer has been specifically designed for the wine and beer maker. It covers a relatively broad range, and therefore, eliminates the need for several instruments of narrower ranges to get the job done. A hydrometer is an instrument for measuring the density of a liquid in relation to water. Water is given the arbitrary figure of 1.000, and other liquids are compared to this figure. The result is said to be their Specific Gravity (S.G. for short). As you add sugar, malt extract, honey, or other soluble solids, the numbers after the decimal point will increase. As the beverage ferments, the sugars are converted into carbon dioxide and alcohol (lighter than water), the numbers will decrease.

DETERMINING ALCOHOL CONTENT

Hydrometers have many uses, but the most common use by wine, beer, and mead makers is determining the alcohol content of a homemade beverage. This is quite simple, actually. 1) First, you must take a reading prior to fermentation. It is impossible to accurately determine the alcohol content of a fermented beverage without this initial reading. Your hydrometer should have a scale called the "Potential Alcohol" scale. This scale measures the amount of alcohol that will be potentially produced if fermented to dryness (S.G. 1.000 or less). The easiest way to take a reading is to sanitize a wine thief or "gravy baster", then remove a sample of the "must" or "wort" and place this in the test stand (this can even be the plastic tube the hydrometer comes packed in). Fill the stand about 3/4 full, then carefully place the hydrometer in it. Give the hydrometer a gentle spin with your thumb and middle finger. This should remove any air bubbles that might otherwise cling to the sides of the instrument. When the hydrometer has settled, take the S.G. (and/or potential alcohol) reading with your eye at the surface level of the liquid. Read the scale inside the instrument at the level where the liquid contacts the glass. 2) After the fermentation is completed, take another reading. Subtract the potential alcohol reading at this point from the potential alcohol reading prior to the fermentation. The difference between the two numbers is the alcohol content that you have actually produced. For example: if the initial reading is 13% and the final reading is 1%, then the actual alcohol content is 12% (or 13% - 1% = 12%). Please note that if your beverage ferments completely dry (S.G. of 1.000 or less), then the alcohol content is the same as your original potential alcohol reading (in the above example: 13% - 0% = 13%). The reason that the final gravity might end up lower than water is that you are producing alcohol, which is noticeably lighter (less dense) than water. All dry wines and meads will finish at gravities lower than 1.000 (e.g. .995). Almost all beers and sweeter wines & meads will finish higher than 1.000.

USES FOR WINEMAKERS

The hydrometer can be used to determine the natural sugar content of the "must." In most instances additional sugar should be added to this "must" to assure that the alcohol content of the finished wine is sufficient for the wine to keep. Alcohol is a preservative, and you should insure that your wine have alcohol content of at least 9 - 10%. Lower strength wines will be susceptible to spoilage. By determining the natural sugar content you can then adjust the sugar content to the desired S.G. reading. In many cases a S.G. of 1.090 is desired to begin the "must," as this give a potential alcohol by volume of 12%.

PROCEDURE FOR WINEMAKERS

1. After sanitizing a wine thief or gravy baster, remove a sample of the "must" and place it in the test stand. Take a reading, then refer to the accompanying hydrometer chart. This will indicate the natural sugar content in the"must."
2. To determine how much additional sugar is necessary to bring the "must" to the desired S.G. (let's say 1.090), use the attached chart. For example: If the initial gravity reading is 1.040, then each gallon of juice contains the equivalent of 1 lb. 1 oz. of natural sugar content. If you consult the chart, at the desired level of 1.090 (12% alcohol), the sugar content should be 2 lbs. 6 oz. Now do the arithmetic.

(desired O.G.) - 1.090, there is: 2 lbs. 6 oz. sugar per gallon
(initial O.G.) - 1.040, there is: -1 lb. 1 oz. sugar per gallon
difference (sugar to be added): 1 lb. 5 oz. sugar per gallon

By subtracting the two sugar contents, you determine how much additional sugar should be added per gallon. It is not necessary (but still not a bad idea), to dissolve the sugar in some boiling water before mixing into the "must."
3. Note that as a general rule of thumb, 1 lb. of sugar dissolved in 5 gallons of "must" will raise the potential alcohol content by approximately 1%. Therefore, if you check the gravity of the must and it reads a potential of 9%, and you wish to produce 12%, simply add 3 lbs. sugar. Note, this is for 5-gallon recipes.

HYDROMETER CHART

S.G.
Potential Alcohol % by Volume	Amount of Sugar in the Gallon lb. oz.
1.010	0.9	--2
1.015	1.6	--4
1.020	2.3	--7
1.025	3.0	--9
1.030	3.7	-12
1.035	4.4	-15
1.040	5.1	1 -1
1.045	5.8	1 -3
1.050	6.5	1 -5
1.055	7.2	1 -7
1.060	7.8	1 -9
1.065	8.6	1 -11
1.070	9.2	1 -13
1.075	9.9	1 -15
1.080	10.6	2 -1
1.085	11.3	2 -4
1.090	12.0	2 -6
1.095	12.7	2 -8
1.100	13.4	2 -10
1.105	14.1	2 -12
1.100	14.9	2 -14
1.115	15.6	3 -0
1.120	16.3	3 -2
1.125	17.0	3 -4
1.130	17.7	3 -6

TEMPERATURE CORRECTION

Please note that most hydrometers are calibrated at 60°F and sample temperatures higher or lower than this will need to corrected. Consult the accompanying correction chart to determine the amount of the adjustment. For example: if your sample reads 1.045, but it is at 84°F, then you need to add .003 for an adjusted reading of 1.048.

TEMPERATURE CORRECTION CHART

 

Temperature of sample (°F)	Reading Correction
50°	-.0005
60°	.000
70°	+.001
77°	+.002
84°	+.003
95°	+.005
105°	+.007