What is Mashing?

Mashing is a key process in making grain beers, and it is not a modern discovery. It's the way beer has been made for centuries and the way it still is made by commercial breweries and serious home-brewers.

Mashing is soaking malt grains in hot water for an hour or two. During this time the starch in the malt (which isn't fermentable by brewer's yeast) is converted into sugar (which is).

To create the right conditions for the conversion to take place, the mash needs to be controlled for temperature and acidity (actually a measurement called 'pH'). The ideal conditions are as follows:

Temperature:
Aim for 67°C, but anything between 62°C and 68°C will work (lower temperatures create a dry beer, high temperatures a sweeter beer).

Acidity
Between pH 4.5 and pH 5.6 - higher pH (lower acidity) produces a sweeter beer, low pH (higher acidity) produces a drier beer. However, sweetness is best adjusted using mash temperature, as varying the pH can lead to problems (e.g. slow conversion or hazes in the finished beer). Aim for pH 5.3 for English style beers. You can measure it using pH indicator papers obtainable from home brew suppliers.

My Set-up

I use a Thorne brewing boiler as my 'mash tun'. I have fitted insulation round it to help keep a constant temperature throughout the goods during the mash. Temperature is maintained by supplying a low voltage to the element using a variac (I have ditched the boiler's original thermostat).

The first stage is to add the mixed dry grain to hot water in the mash tun, a process known as 'doughing in'.

The water needs to be hotter than the desired mash temperature, because the cold grain cools it down. The temperature of the water is known as the 'strike temperature'.

A number of factors affect the final mash temperature, including the ratio of grain to water, the temperature of the grain and the thermal characteristics of the equipment itself.

I find that with a strike temperature of around 73°C, the mash temperature settles to about 67°C, which is what I want.

pH is determined by two main factors; the quantity of grain and the amount of water. More water raises the pH, less water reduces it. Using dark malts also increases acidity. In other words, unless your water supply is very unusual (see below), the pH is automatically set by the recipe.

Most books will tell you that the mineral content of your water is critical for successful mashing. This is true to some extent, but as long as you don't have very chalky water (in which case you can boil then filter your water first) you shouldn't have a problem producing a good beer. You may  have to experiment a bit to get the mash pH right, because that is what is really critical. I will be adding a page on water treatment soon.

I mash at around 67°C, as I like a bit of residual sweetness to balance the bitterness of the hops; this also means the mash is completed sooner.

I allow the mash to carry on for 1 hour 15 minutes, then transfer the goods to a separate bucket fitted with a grain bag for sparging.