This is the third installment in the All-Grain Brew Day Walkthough, which started with a post on strike water preparation.
Once the brewing liquor is heated and the grist is crushed, it’s time to mash in. Mashing in, or doughing in, is mixing the hot strike water with the crushed grains so they come to rest at the target mash temperature and thickness. Homebrewers have a few options when it comes to mashing in.
Mash Temperature and Thickness
Most single infusion mash recipes specify a mash temperature in the 148–162 °F (64–72 °C) range. Optionally, the mash may be heated to 168–170 °F (76–77 °C) following this for a mash out. Mash tun space for homebrewers is frequently limiting, and mash thicknesses in the 1.0–1.5 qts./lb. (2.1–3.1 L/kg) range are common, although thinner mashes [up to 2.4 qts./lb (5.0 L/kg)] are workable. A lot of moderate-bodied ales are made by mashing at 152 °F (67 °C) at 1.25 qts./lb. (2.6 L/kg). Mash times are frequently 60 minutes, although shorter times may work just as well.
The temperature of the mash is determined by the temperature of the strike water, crushed grain, and your equipment. Homebrewers can calculate their strike water temperature, or arrive at it via trial and error. As a rough rule of thumb, if your equipment and grain is that “room temperature,” heating the strike water to 11 °F (~6 °C) above your target should yield the correct mash temperature. [This assumes a mash thickness of around 1.25 qts./lb. (2.6 L/kg).]
Most homebrewers mash in their mash/lauter tun. This is convenient because, once the mash is over, you simply open a ball valve to start recirculation. However, if you are using a modified picnic cooler as a mash tun, or any other type of mash tun that is not heatable, there are some times when mashing in your kettle is the best choice.
Mashing in your kettle allows you to perform step mashes. It also allows you to heat the mash to maintain a steady temperature, stir the mash to improve extract efficiency, and heat the mash to mash out temperatures. The only downside is that you need to scoop the mash to your lauter tun when you’re done, and rinse out your kettle. Of course, if you have a heatable mash tun, you can benefit from all these things without having to transfer your mash from your kettle to your lauter tun.
Pre-Heating the Mash Vessel
Many homebrewers preheat their mash tun by filling it with water at or above their projected mash temperature. This can be a good idea if your mash tun is not heatable, or is not heated during your brewing day. This is doubly true if you are brewing outside and your equipment is cold. If your mash tun is heatable, this is not needed.
There are at least three options for mashing in — pour hot water into the crushed grains, stir crushed grains into the hot water, or mix the two as you go. Of these options, adding water to the dry grain is the worst. This tends to wet the grain into lumps or “balls” of wet grain surrounding dry interiors. It takes a lot of stirring to break these clumps up and evenly mix the water and grains.
Stirring the grains into hot water is a better option. This wets the grains completely as they enter the water and it’s relatively easy to stir the grist in to the brewing liquor. In addition, you can add the hot strike water to the mash tun and let it sit for about 5 minutes to pre-heat the mash tun. If the temperature of the water drops too much, drain some or all of the water back your hot liquor tank and heat it again.
A third mash in option also has several benefits — adding the grains and water at the same time. If you take two “scoops” of the same volume — beer pitchers, large measuring cups, etc. — mixing one scoop of water and one scoop of crushed grain yields a mash thickness around 1.0 qt./lb. (2.1 L/kg), depending on how finely the grains settle in their scoop. As such, one option for mashing in is to alternately add a scoop of strike water followed by scoop of grain until the grain is gone. The mash can be stirred as it is slowly layered in. As you approach 2/3 to 3/4 mashed in, you can take the temperature to see how close you are to your target. If needed, you can heat your remaining strike water to a higher temperature or stir in some cold tap water to bring the temperature down. As you near being completely mashed in, the mash will be somewhat thick (around 1.0 qt./lb. or 2.1 L/kg). As such, pour in the correct amount of strike water to hit your target mash thickness. (If you’ve heated the correct volume of strike water in your hot liquor tank, simply stir in that water once all the grains are wet.)
Once you are mashed in, put a lid on your mash. If you can’t add heat to your mash tun, and need to retain as much heat as possible, insulate it with blankets or other insulating materials. After 5 minutes or so, take a small sample of wort to measure your pH. Take the sample in a small cup or jar and cool the container in ice water until the sample is at room temperature. This shouldn’t take long as you only need a volume of wort large enough to submerge the pH electrode in.
The pH of the cooled sample will be approximately 0.35 higher than the actual pH at mash temperatures. (At higher temperatures, the pH of an aqueous solution decreases as more hydronium ions (H3O+) are formed from water. Note, more hydroxl ions (OH–) are also released, so the overall acidy or alkalinity of the solution does not change.) In the brewing literature, it is sometimes unclear how a measurement was taken. And, in the homebrew literature, the advice on how to interpret published pH values varies. Briggs, et. al., in their book, “Brewing: Science and Practice” (2004, Woodhead) say, ”Infusion mashes are best carried out at pH 5.2–5.4 (mash temperature), and so will give cooled worts with pH values of about 5.5–5.8.”. [Ed. But see commentary in comments section.] If you are brewing a dark beer and have added carbonates to your water, don’t worry if the pH is too low initially. Keep taking the pH over the course of the mash and you will likely see the pH drift into the right zone. It takes a little while for the carbonates to neutralize acidity.
In your brewing notebook or brewing software, take a note of the volume of strike water you used, its temperature, and your initial mash temperature. (You should already have the details of the grist written down.) If you made any adjustments, note what those were. This will help you adjust your procedures, if needed, to make things go more smoothly next time.
Next up, what to do during the mash.