Mashing is part of the all-grain brewing process. Put simply, it is the act of mixing malted grains with hot water to convert their starch into sugar, it is this sugar which the yeast convert into alcohol giving us beer. Mashing is half science, half art; there are many different ways of mashing grains, and everyone does things slightly differently to eachother. When you are starting all-grain brewing for the first time, it is best to stick to the tried-and-tested methods of mashing, and find one that’s good for you. In this post I will be summarising the four basic mash types, and with a little help from various online sources will try to explain what makes each one different.

Mashing Grains

The Four Basic Types of Mashing

1. Single Infusion Mash

The Single Infusion Mash is the the most simple, and arguably the most popular mashing method for homebrewers to use. In an infusion mash, room temperature crushed grains are combined with a premeasured amount of hot water at an exact temperature. By taking the temperature of the grain, amount of water needed, and the mash tun’s properties the homebrewer can determine the exact water temperature needed, to ensure that combined with the grains they will achieve a mash in the 148 to 158 F temperature range. Infusion is typically done at a water to grain ratio of around 1.25 quarts per pound of grain. The easiest way to calculate the proper infusion volume and temperature is with an infusion calculator or brewing software such as BeerSmith or Rackers.org. The mash is then held at that temperature, usually by keeping the mash in an insulated cooler for 45-90 minutes. At this temperature, the mash will readily convert starches into sugars. You can test for conversion of sugars using an iodine test. Simply draw a small quantity of mashed grains out, add a few drops of iodine to it. If the iodine does not turn blue, then the conversion is complete.

Types of Mashing

2. Temperature Mash

The Temperature Mash is an alternative to the Infusion Mash. Rather than adding a known quantity of hot water, the mixed water and grains are simply raised to the target mashing temperature and held at that temperature until the starch conversion is complete. While this is quite practical for a commercial brewer, temperature mashing presents challenges to home brewers. Most homebrewers use simple pots over a stove or propane burner, and it is difficult to hold a precise mashing temperature for an extended period using just a stove and pot. A popular homebrewing method for acheiving a stable temperature mash is the use of a HERMS (Heat Exchanged recirculating Mash System), or RIMS (Recirculating Infusion Mash System). These systems are expensive, complex, and are usually used by more experienced home brewers. You can find more information about HERMS and RIMS brewing here.

Commercial Copper Mash Tun

3. Decoction Mash

Dcoction mashing is a traditional German mashing method. In a decoction mash, some of the mash including both grains and water is moved to a second container where it is brought to a boil. The boiling mixture is then added back to the original mash to raise the temperature of the overall mash. Again, a calculator or brewing software is needed to accurately calculate the correct volume to decoct. Traditional decoctions were typically done at higher water to grain ratios of 2.0 qt/lb or more (a thinner mash). More modern techniques often use water to grain ratios closer to the 1.25-1.5 qt/lb range.

Big Mash Tun

4. Multiple Step Mashes

Multiple step mashes are very complex, and are not suitable for novice brewers. Although a single infusion mash is suitable in 95% of cases where modern well modified malts are used, some precooked adjuncts and undermodified malts require protein rests at lower temperature before the main saccrification (sugar conversion) step. These protein rests help to break down complex starches in preparation for saccrification. Infusion, temperature and decoction steps may be combined to achieve multiple step mashes. For example a complex three step decoction mash might start with an initial infusion step to an acid rest at 105 F, followed by a protein rest at 122 F, and a saccrification step at 155 F. In many mash profiles, a mash out step is used to raise the temperature of the entire grain bed in preparation for sparging. The mash out step helps to halt saccirifcation, and also helps ensure an efficient sparge by extracting sugars at a higher temperature.

Thanks for reading!
- Brewing-Tips.com Staff
Source: http://www.brewwiki.com/index.php/Mashing