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Wort Boiling
Operating the Kettle
Traditionally, kettle times lasted between 90 and 120 minutes, with a minimum of 10% evaporation per hour. However, today kettle times for an all-grain beer last from 60 to 90 minutes, with a 5 to 8% evaporation rate. Boil times of 2 hours or longer are usually reserved for special beers, such as strong Scottish ales. In order to save time, most brewers begin applying heat as soon as the wort covers the bottom of the kettle to minimize charring (or scorching), and to prevent damage to the kettle. Some systems may require that the kettle be more than halfway full before applying heat. Care must be taken when using direct gas fire since the first runnings are easily caramelized. If steam jackets are used, heating may be started as soon as several inches of wort are in the kettle by shutting off the side jacket.
Click on the following topics for more information on wort boiling.