Tuesday, January 15, 2008
Part 1 of Using Your Hydrometer deals with how to measure the sugar content of your must or wort. There are a couple of things you need to know to get an accurate measurement.
Most hydrometers are calibrated to give correct readings at 59-60 degrees Fahrenheit. Higher temperatures thin the liquid slightly and result in lower readings than you'd get at the correct temperature. At 70 degrees F., the reading will be 0.001 low. To correct it, add 0.001 to the reading. At 77 degrees F., add 0.002. At 84 degrees F., add 0.003. At 95 degrees F., add 0.005. At temperatures above 95 degrees F., you risk killing your yeast and losing your wine. If you can't remember all that just print out the chart below.
Another thing you need to know is that most hydrometers come with three scales. Specific Gravity, Balling and Brix are the ones that are usually on your hydrometer. Specific Gravity and Brix are the ones that are most used. Sugar can be measured as ounces per gallon or as degrees Balling, or Brix. Ounces per gallon are measured on a numeric scale in which an S.G. of 1.046 equals 16 oz. (one pound) of sugar per U.S. gallon. Brix is measured as a percentage of sugar by which pure water has a Brix of 0 (or 0% sugar), an S.G. of 1.046 equals a Brix of 11.5 (11.5% sugar), and an S.G. of 1.095 equals a Brix of 22.5 (22.5% sugar). If you have a choice and want to simplify your life, buy a hydrometer that measures sugar by ounces per gallon .
Lastly, the real reason why we use a hydrometer is to make the perfect wine. Here's a guide to the amount of sugar that should be used. Table wines are generally started at an S.G. of 1.090 or higher and fermented to dryness--0.990 to 1.000. Sweeter wines are started at a higher S.G. using a yeast that will die out at predictable point and stabilized at that time and at the desired sweetness to prevent die-hard yeast cells from re-populating the wine, or, more commonly, started at 1.090 or higher, fermented to dryness, stabilized, and sugar added back to the wine to sweeten it. The 1.090 specific gravity is a rather magical number. It produces an alcohol level of about 12.3%, a level that ensures the wine's preservation. I usually start at 1.095, or about 13% alcohol, because I know I will lose some volume in racking and add water to make it up, thereby diluting the wine and the percent alcohol by volume. In truth, a hair over 10% alcohol is all that's required to preserve grape wine. But some fruit wines actually require the 12% level for unrefrigerated preservation, so using 12% as a rule of thumb errs, if at all, on the side of safety.
That should cover everything you need to know about your hydrometer and how to use it.
Using Your Hydrometer - Part 1
Brix Scale Calculations