Decoction mashing can seem like an impassable mountain on your hero’s journey as a homebrewer. It offers the promise of deeper malt character, but the extra time and work are too daunting for some. Brewing masters contribute to the mythology as they debate using single, double, or even triple decoction schedules.
Decoction Demystified
But don’t believe the hype; decoction mashing is actually fairly simple. All it involves is pulling off a portion of the mash and boiling it for some time before adding it back in. The qualifiers—single, double, triple—refer to how many times the process is repeated within the context of step mashing. A full step mash schedule may include an acid rest at 95─113°F (35─45°C), a protein rest at 131─138°F (55─58°C), saccharification at 142─160°F (61─71°C), and mash out at 168─170°F (75─77°C). Decoctions can be used to heat the mash from one rest to another. Typically a single decoction is used to move from saccharification to mash out, but the extra rounds can be used with additional rests in the schedule.
So why bother? The biggest justification is somewhat outdated. Most malts today are highly modified, but that wasn’t always the case. The full step mash evolved to deal with under-modified malts, and boiling a portion of the grain prepares those malts to be more effectively mashed. Another part of the appeal is that it’s a traditional touchstone that connects modern brewers with their European forebears, and many would claim you can’t make a real German lager without a decoction mash.