The partial mash (or mini-mash) method of preparing wort is essentially a fusion of the extract and all-grain methods.  The homebrewer gets more control over the finished product like with the all-grain method while being able to use the same equipment needed for the extract method.  In a nutshell the partial mash method of preparing wort utilizes the mashing of malted grains in addition to using malt extract to get all of the fermentable sugars need to make the beer.  For many homebrewers the partial mash method of preparing wort is a way to try out the mashing process while still having the safety net of malt extract to fall back on.  Here at the Homebrew Garage we see partial mash brewing as a good compromise for the homebrewer ready for more of a challenge but who isn’t quite ready to get into all-grain. 

As mentioned above you can brew using the partial mash method of preparing wort using the same equipment used for extract brewing and adding in a few simple items you probably already have in your kitchen anyway. 

Essential Equipment For Making a Partial Mash Wort 

In addition to the equipment needed for the extract method you will need: 

-         Stock pot (or similar) for heating sparge water

-         Stainless steel or food grade plastic colander

-         Bottling bucket (or similar plastic bucket)

-         Kitchen scale for measuring grain

-         Floating thermometers (2 are really needed) 

Procedure

Mashing 

Consult the recipe you are following and add up the total weight of the grain.  Add about 1 quart of water per pound of grain (i.e. 4.5lbs of grain = 4.5 quarts of water) to your brew kettle.  Put the brew kettle over a medium high flame and heat the water to between 165-170 degrees Fahrenheit.  Once the water is at the correct temperature remove it from the heat and gradually stir in your crushed grain.  Mix the crushed grain (called grist) thoroughly and then check the temperature of the mash with a thermometer.  The target temperature can vary by recipe, but you are generally shooting for a temperature of between 150-158 degrees Fahrenheit.

If the temperature of the mash is too low the enzymes needed to convert the grain starches into sugars will be inefficient.  This is remedied by gently applying heat while stirring constantly.  If he mash temperature is too high (over 168 degrees) you can cause the grist to release harsh flavors knows as tannins.  If your mash is too hot quickly add small amounts of cold water and stir continuously until the temperature falls back to the target zone.  Once the temperature of the mash has stabilized put the cover on the brew pot and let science do its thing!

Depending on the recipe you will usually mash for 60 minutes so make sure to check the temperature from time to time to make sure the mash stays at the appropriate temperature.  Once the mash is complete you have the option of raising the temperature to 168-170 degrees and holding it there for 10-15 minutes in a process knows as a mash-out.  The mash-out stops starches from being converted into sugars and warms the grain bed to prepare it to have the sugars washed out.  If you choose not to do the mash-out you can proceed right to sparging.

Sparging 

While you are finishing up the last 15 minutes or so of the mash, heat 2 quarts of water for each pound of grain to 170 degrees in a separate pot.  This heated water is knows as sparge water.  Once the mash is finished (and mash-out if you did one) suspend the colander or other fine strainer over your bucket.  Carefully pour or spoon the mash into the colander and allow it to drain as much of the sweet wort as possible into the bucket.  Let gravity do the work for you and resist the temptation to help things out by pushing on the grain with your hands!

Once all the sweet wort is drained out take the colander out of the bucket and suspend it over the brew kettle.  Gently pour the sweet wort from the bucket back over the grains where it can drain into the kettle.  This step helps set grain bed and filters out many of the pieces of husk and other debris from the grist.  Once this is complete gently pour the sparge water over the grain bed.  It is best to try and equally distribute the sparge water over the grain bed so that it doesn’t become compacted in one spot and so that the sugars are washed out evenly.  It is also best to try and keep some of the sparge water on the grain bed all the time to keep it from being dry.

Once you have poured all the sparge water over the grain, give the grain bed a few minutes drain out so as much of the wort can be collected in the brew kettle as possible.  Again, let gravity do the work as you don’t want to push anything unwanted out of the grain and into your wort.  Once all the wort has been collected remove the colander from the brew kettle and stir in the malt extract called for by your recipe.

Whew!  That wasn’t too bad was it?  You have just prepared a partial mash wort and now have a good idea of what it will be like to do it on a bigger scale if you decide to tackle all-grain!