All-grain homebrewers can make the vast majority of beer styles using a simple single-temperature infusion mash. Hot water and milled grain are combined to achieve a specified mash temperature, usually around 148–156°F (64–69°C), and then the mix is held for 60 to 90 minutes before lautering. Today’s highly modified malts make such straightforward mash techniques possible and place all-grain methods within the reach of most brewers.
The beauty of the single-temperature infusion mash is that it strikes a compromise between the activities of beta amylase and alpha amylase enzymes for the sake of simplicity. A handful of beer styles, however, such as Pilsner, Märzen, Bock, and other Continental lagers, can benefit from a more involved mash schedule. This is especially true when they’re built upon certain malts from Germany, Belgium, and the Czech Republic, which can be (though certainly not always are) less modified than those from North America and the United Kingdom.
Multi-rest mashes carry the grain bed through an increasing series of temperatures to favor different enzymes at different lengths of time. Historically, such mashes may have included acid rests, beta-glucan rests, protein rests, and other low-temperature steps. Today’s malts, however, rarely need to spend any time in these regimes, even less-modified malts. Thus, a modern multi-step mash may only spend some time in beta-amylase territory before jumping to the alpha-amylase rest and mash out.