Methods of Modern Homebrewing by Chris Colby

Author:Chris Colby
Language: eng
Format: epub
Publisher: Page Street Publishing Co.
Published: 2017-11-02T04:00:00+00:00

A full wort boil should be vigorous, but not so vigorous that the wort is scorched. One way to measure the vigor of the boil is to measure the volume of wort evaporated in a given time period. It’s typical for homebrewers to boil away about 1.0 gallon (3.8 L) per hour. In the case of 6.0 gallons (23 L) being boiled down to 5.0 gallons (19 L), this is 16.7 percent of the wort evaporated per hour. This is slightly higher than comparable commercial boils, which typically evaporate around 10 percent per hour, and works well for most homebrewers. Some homebrewers need to keep their kettle partially closed to achieve a vigorous rolling boil. This is fine as long as the steam still has a path to escape. If you cannot maintain a rolling boil without closing the kettle’s lid, you need a more powerful burner. Throughout the boil, periodically check on your boil vigor. If you need to cover the kettle partially, do so, but be prepared to open it back up if the wort begins to boil too vigorously.

As the volume of wort shrinks, the concentration of wort sugars increases. If a brewer measures the pre-boil wort volume and specific gravity, and knows the target wort volume, it is easy to estimate the post-boil wort density by using this equation:

C1V1 = C2V2

where:

C stands for concentration (in °Plato or “gravity points”)

V stands for volume (in gallons or liters)

1 and 2 stand for the pre-boil and post-boil worts, respectively

For example, if a brewer collects 6.0 gallons (23 L) of wort at SG 1.044 and plans to boil it down to 5.0 gallons (19 L), the estimated post-boil specific gravity would be [44(6) = C2(5), C2 = 264/5, C2 = 52.8] 1.053.

After a short time boiling, the brewer should see the hot break begin to appear. If the break material looks large and fluffy—almost like large snowflakes—this is an indication that the wort pH is in the right range. Hot break production is maximized around a pH of 5.2.

If the break pieces are all tiny, the brewer should adjust the wort pH. If the hot break consists of tiny bits, the problem is almost always that the pH is too high. This can almost always be remedied by adding a small amount of calcium to the boil. If the pre-boil wort volume is 6.0 to 6.5 gallons (23 to 25 L), add 0.50 teaspoons of calcium chloride to the wort. This will add about 50 ppm of calcium ions to the wort when it is boiled down to 5.0 gallons (19 L). Add (roughly) proportionally more or less for worts of other volumes. If this doesn’t have the desired effect, add a second dose of the same amount of calcium. If the second addition doesn’t have the desired effect, further additions won’t help.

Stirring the wort can be helpful, especially stirring so the top and bottom of the wort get mixed as well as rotated in the kettle. However, the action of the boiling itself is going to mix the wort on its own.

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