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Using the Hydrometer


Many people fight shy of the hydrometer, but in beermaking it is virtually a necessity, for it can tell you, with certainty, exactly when it is safe to bottle, thus avoiding dangerous explosions later which may result if you bottle by guesswork. With heavy beers, using up to 2 lb. of malt and/or sugar to the gallon, you can bottle when the S.G. is below 1010, with light beers, using up to 1 lb. per gallon, when the S.G. is below 1005.
But it has other uses: with its aid you can calculate reasonably accurately the right amount of malt and/or sugar to produce a beer of any specified strength, thus removing the guesswork from your brewing. Before mashing grain malt you can test your malt and know what gravity you can hope to achieve with a particular batch of malt; minor adjustments can be made to the prepared wort by means of sugar. You can also check upon the progress of a fermentation.

The word hydrometer means "water-measurer" but it is more accurately called a saccharometer, or "sugar measurer", for its basic purpose is to discover how much sugar there is in the wort. Fermentation uses up the sugar to produce alcohol and carbon dioxide; therefore if we can discover how much sugar is used up during a ferment, we can calculate exactly how much alcohol has been produced, and how strong the resultant beer is.The more sugar there is in a liquid, the thicker or denser it will become, or the greater its gravity will be. The better, too, it will support anything floating in it; the hydrometer makes use of this principle. To measure different gravitates, we naturally need a scale of some sort, and an obvious and convenient standard from which to start is that of water. Water is therefore given the arbitrary gravity of 1.000, other liquids are compared specifically with this, and the resultant figures are said to be their specific gravity. Thus, liquids heavier than water (or, in our case, containing more sugar) may have specific gravities such as 1.050, 1.120 or 1.117 degrees. When talking of gravities, however, we omit the first "I" and the decimal point. Therefore the specific gravities quoted are exactly the same as gravities of 50, 120 and 11 7 respectively. For brewing you will need, a hydrometer covering the range 1.000 to 1.100. The hydrometer is a glass tube (with a bulbous lower end containing the scale, and it is weighted at the bottom so that it will float upright in a liquid. The reading is taken where the level of the main surface of the liquid would cut the scale.

The thinner the liquid (the less its gravity) the deeper the hydrometer will sink in it; the denser the liquid (the greater its gravity) the higher the hydrometer will float, and the more ,the scale will protrude above the surface. Therefore the scale of figures in the hydrometer is "upside down", the smallest being at the top and the largest at the bottom. In water, of course, the hydrometer will float with the 1.000 mark level with the surface; as you add sugar so the hydrometer will rise in the liquid. If, on the other hand, you add instead to the water a liquid lighter than water alcohol, for instance-the hydrometer will sink below 1.000.

To use your hydrometer pour some of the wort to be into a hydrometer jar. Spin the hydrometer to get rid of air bubbles clinging to its side, which can seriously affect the reading, and then, when the hydrometer is still, take the reading, with the eye at surface level.Having obtained the reading, you can then check with the table as to whether your wort is of the correct strength, or whether any sugar needs to be added to bring it up to the desired potential strength, but it is as well not to add all the sugar at this stage. Leave a margin so that the wort can be readjusted after boiling. Rough guide: 2½ oz. of sugar will raise the gravity of a gallon by roughly five degrees; I lb. of sugar added to one gallon will raise the S.G. by about 35.

The hydrometer does simplify matters; after making up the wort, check the specific gravity to see how much total sugar it contains. It is then simple, with the aid of the following table, to calculate how much sugar, if any, needs to be added, to attain exactly a wort of any desired gravity. Thus, if you wish to make a beer of 7 per cent (1055) and your wort shows a gravity of 1040, you will need to raise the gravity by 15 degrees (1055 less 1040) and reference to the table will show that you will need to add 5 oz. of sugar to the gallon to obtain that result (i.e. to reach S.G. of 1055).

With very strong beers, it is advisable to add half the sugar at the outset of fermentation, and the remainder after the first three days or the fermentation may stick. With strong, average, or weak beers this is not necessary.
Information source www.valleybru.com/tips.htm



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