Mashing 101

By Jon Griffin

Mashing is simply the conversion of complex sugars, which are developed during malting, into simpler sugars that yeast can metabolize.

There are 5 main types of mashing, but we are interested in only 4 of them in this class. They originated in different areas and helped create the classic beer styles of the world. Mashing techniques evolved based on climate and malting technique. In Europe most of the Maltsters, made under modified malt, whereas in the British Isles they used fully modified malts.

Historically the Picts created alcoholic beverages in 6500 BC, although no one really knows what they would have tasted like. The Vikings passed down brewing sticks for generations and yeast evolved on them to create ancestors to the very yeast used today for brewing. Belgians have always used wild yeasts and bacteria in their beers, and it wasn’t until the mid 1800’s that the Germans and French determined what yeast really were. By the late 1800’s a chemist a Carlsberg brewery isolated the yeast strain that made lagers and modern yeast knowledge was vastly improved.

Mash Types

In the British Isles from at least sometime before the 11th century all the way up to the early 1700’s the process used was called Parti-Gyle. This is a very simple technique and basically was mixing the crushed grains and water in a container. After it sits for a time, a plug was knocked out and all the liquid was released. Using this technique, after the first runnings were put to boil, the plug was reinserted and the process repeated to make a beer of the second runnings. This was sometimes even repeated for a third time.

The first runnings had a high gravity, and consequently more alcohol. The second runnings were much smaller and the third smaller still. Often times, the third runnings were left for the women to drink.

As a side note, all brewing at this time was done as a type of Parti-Gyle. In Belgium, they used a turbid mash, which was a modification of this technique.

Sometime around the middle to late 1800’s (possibly earlier), the people of Scotland invented a mashing process known as the Infusion Mash. Infusion mashing is probably the most widely used type of mash process today.

Infusion Mash

Infusion mashing (also called single step mash) started as a single step process, but as you will see the Belgians improved this further. In the infusion mash, the crushed grains are mixed with water at a temperature desired for the beer style. This is generally from 140 to the mid 160’s. Lower temperatures create more alcohol, and higher temperatures create more dextrins (increased body). They also added a mash out step. The wort temperature is raised to about 175F for 10 minutes. This stops all enzyme production. Then the wort is re-circulated until it is clear. After this the run-off is directed to the boil kettle this step is called sparging.

Step Mash

Step mashing is a Belgian modification of the infusion mash. It is also called a multi-step infusion mash. As it’s name implies instead of just one temperature rest, the grist is infused with different temperature water creating a series of “steps”. The reason for this is that continental malt was under-modified and needed a protein rest to convert protein as well as the sugar rest. There could be as many as 5 steps, but we are mainly interested in the protein and sugar rests. Other than these changes, the mash out, re-circulation and sparging are the same as infusion mashing.


Decoction mashing is very similar to step mashing, and originated in Germany. The temperature steps are the same, only the technique differs. In decoction, a portion of the grist is removed and brought to a boil through direct heat. It is then returned to the mash and effectively raises the temperature. The single, double and triple decoctions are the most widely used.

Double Mash

Double or American Mashing is used for American Lager style beers where large portions of unmalted adjuncts (such as corn) are used. I mention this for accuracy though you are not required to remember this! In this style, the malted grains are started at the same time as the unmalted grains in separate vessels. A small portion of crushed barley is added to the unmalted grains as a source of enzymes. It is similar to a step or decoction mash and finishes the same way.