Partial Mash Brewing

A partial mash recipe usually involves mashing 3-6 pounds of grain and then using a lesser amount of malt extract (maybe 3-4 pounds instead of 6-7). You can do this without making/buying a mash-tun and a larger pot. All you need is a couple large muslin bags, an extra 1-2 gallon pot and large strainer. More about that later!

Just about every extract recipe involves steeping a pound or two of specialty grains in a couple gallons of water for 10-20 minutes. The desired result is simply to extract the flavors from the grains, not to also convert their starches into fermentable sugars.

Many specialty grains yield little fermentable sugars when mashed. This is due to the malting and roasting processes. Crystal malts, chocolate, roasted and black barley, Cara-Munich and Cara-Vienna and Special-B are some of the specialty grains that add flavor but very little fermentable sugars when mashed. If these are the only specialty grains in your extract recipes, there is no need to mash them.

If your recipe calls for German or Belgian pilsner, Munich, Vienna, wheat, golden promise, mild or 2-row malts, you can benefit from doing a partial mash and reducing the amount of liquid or dry malt extract required in your recipe. You can also do a partial mash to get the feel of all-grain brewing before you decide to spend the additional money on a mash-tun, larger boil pot, and wort chiller.

Don’t panic when we start talking about mashing grains! We’re still going to steep some grains in hot water in muslin bags. The main difference is that we’ll start with only a gallon of water heated to a specific temperature (instead of a broad range) and steep them longer, drip and rinse again, and still end up with 2 to 2-1/2 gallons of liquid to boil. Like Charlie Papazian says, “Relax, have a homebrew!”

My target partial mash recipe for this article is a Belgian Wit, which calls for about 40% white wheat and 60% Belgian Pilsner for the base malts in an all grain recipe. I’ve yet to find white wheat extract in either liquid or dry form, so this would be the perfect recipe to do a partial mash.

As I mentioned above, you’ll need an additional pot with at a one to two gallon capacity, a large strainer basket or colander and two large muslin bags. My strainer has a long handle I can place atop my boil pot and not have to hold it as the grain bags drip. I have a couple dutch oven pots that hold 1-2 gallons of liquid. If you have a glass lab thermometer, it will make your temperature checking easier.

Typical Igloo cooler mashing involves starting with 1 quart of water preheated to 170 degrees for every pound of grain being mashed. After adding the grains to the warm water, the temperature should equalize out between 150-152 degrees and then held for about one hour. Yes we are picky about our mashing temperature! Temperatures cooler than 150 won’t convert the starches into sugars, and at 156 or above, creates more unfermentable dextrines that would give us sweet brews with low alcohol. Because we don’t have to warm up a plastic cooler, we’ll start with water a little cooler.

Our recipe for the Belgian Wit will involve mashing 5 pounds of grain and making up the balance of the wort sugars with 3 to 3-1/2 pounds of extract to get an original gravity between 1.050 and 1.054. Note you could use 5 pounds of different grains to make a pale ale, cream ale or Kolsch but the mashing process would be the same.

Ingredients and partial mash instructions for the Belgian Wit:

• 4 pounds white wheat
• ½ pound caraform or carapils
• ½ pound of 6-row barley (helps to convert the wheat starches)
• 3 to 3-1/2 pounds dry pilsner or extra light extract
• 2 ounces of Styrian Golding or Liberty hops
• 1 ounce bitter or sweet orange peel
• 1 ounce coriander seed (lightly crushed) or 1/3 tsp ground coriander
• 1 tsp Irish moss (hydrated in 1/3 cup water)
• Wyeast 3944 or White Labs 400 Belgian Wit yeast

Crush the grains and put into two large muslin bags, then tie off the ends. Heat 5 quarts of water in your 5 gallon pot to 158 degrees and then turn off the heat. Put the two grain bags into the pot, rock it around a bit to make sure all the grains get wet, then stick your glass lab thermometer in between the bags and put the lid on. Let this sit for about 5 minutes and then check the temperature. It should be 150 degrees. If you are below 150, turn the heat back on and gently bring the temperature up to 150. If you are above 152, add a couple ounces of cold water, stir or slosh and get it into the 150-152 range. Put the lid back on (heat is off!) and recheck every 15 minutes. At this point, you’ll usually need to gently warm up the mash to maintain the 150-152 range. Maintain this temperature range for one hour!

Take a teaspoon of wort and place in a small bowl or Dixie cup. Add a drop of iodine and note the color change. If the iodine turns black, you need to steep another 10-15 minutes. If instead it does not change color, you are ready to start sparging/rinsing. If you don’t have iodine but kept the temperature between 150 and 152, you are probably done with the mash and can start sparging.

Remove the two grain bags and drip for a couple minutes, then sit aside on a couple plates or in another large bowl or pot. Pour the wort into your 1-2 gallon pot, we’ll save this for later. You should have a little over three quarts. Heat another 5 quarts of water to 180-190 degrees in your 5 gallon pot and then turn off the heat. Return the grain bags to the fresh hot water and slosh around for a few minutes, let stand (without heat) 15 minutes then pick up the grain bags again and drip again. Set them aside as you did before. Pour the original 3 quarts of wort into your 5 gallon pot. If you have a long handled strainer, place that atop your pot and put both grain bags in it.

At this point, you should have 2 gallons of wort. Heat 2 more quarts of water to 180-190 degrees, then slowly do a final rinse of the grain bags with this water into your 5 gallon pot. You should now have 2-1/2 gallons of wort with a gravity about 1.042. Stir in your dry malt extract. If you prefer, you can substitute 3-1/2 to 4 pound of liquid malt extract. After the extracts are mixed in, turn the heat back on and bring to a boil. The rest of the process is the same as any other brew. Add one ounce of hops and boil for 45 minutes, then add the hydrated Irish moss, orange peel and second ounce of hops and boil 10 more minutes. Add the coriander and boil 5 minutes. Turn off the heat.

Fill your fermenter with 2-1/2 gallons of very cold water, then pour in the hot wort. Top off with more cold water to get 5 gallons. When the temperature drops below 80 degrees, pitch your yeast, add your cover and/or airlock, and store the fermenter at approximately 67–72 degrees. Your partial mash brewing session is then complete!

Be sure to check out our partial mash recipe kits