While calculating the overall water necessary to conduct a  full mash , batch sparge  and boil it is important to note how much water will be lost in the spent grains.  I use the basic equations below when calculating the amount of water necessary when brewing an all grain beer.

Amount of Water for Mash = (Pounds of Grain) x 1.25 quarts/pound (divide by 4 to get gallons)

Amount of Water to Batch Sparge with = (Final Boil Volume) + (Shrinkage/Evaporation) + (Equipment Losses) + (Spent Grains) – (Amount of Water for Mash)

From what I have experienced on my brewing rig spent grains absorb about 20% of there own weight in gallons, here is a chart that can be used for reference.  This estimate is based on my single infusion mash with batch sparge  in a 60 quart cooler with a grain crush around .039.

Total Grain Weight in Pounds x .20 = Approximate Gallons of Water Absorbed by the Grains


Pounds of Grains Gallons of Water Lost
5 1.00
6 1.20
7 1.40
8 1.60
9 1.80
10 2.00
11 2.20
12 2.40
13 2.60
14 2.80
15 3.00
16 3.20
17 3.40
18 3.60
19 3.80
20 4.00
21 4.20
22 4.40
23 4.60
24 4.80
25 5.00
mashing in a cooler

mashing in a cooler

All-grain brewing is essentially brewing a beer from scratch and not using any malt extract.  It describes the process by which the sugars from the grains are extracted and become the beer.  The two steps that make up all grain brewing are mashing and lautering.  Hopefully by now you have brewed a few extract based beers and are ready to move onto personalizing your beer even more.   If that is not the case, I recommend you checking out the Basic Brewing articles and getting familiar with the brewing process before attempting an all grain brew.

What is Mashing?

The term mashing is used to describe the process by which malted grains are soaked in a hot water bath for about an hour.  This process gelatinizes the malts starches, releases some natural enzymes, and converts their starches into fermentable sugars. 

The whole process goes something like this:

  • Malt is crushed and added to mash tun (mashing)
  • Malt is soaked with 160-165 water at a water-to-grain ratio of 1.25-1.5 quarts per pound to achieve a mash temperature of 150-155. (mashing)
  • Mash is usually held at that temperature for an hour, then drained into the brew pot. (mashing)
  • Additional water at around 165-175  is then added to the mash. (lautering)
  • Mash is stirred and settles for about 30 minutes then drained off again. (lautering)

Equipment Needed for Mashing

Mash tun —  The easiest type of mash tun to build is a cooler mash tun.  The mash tun will be used to conduct the mash inside, home brewers usually use a cooler mash tun, the other alternative is an expensive pot mash tun with a false bottom. 

Sparge water pot–  A large pot that will be used to heat up your mash water and sparge water.  If you are planning on brewing 5 gallons of beer you are going to want about a 5 gallon pot to use as your mash/sparge water pot. 

Wort boiling pot–  A large pot that will be used as the boil pot, keep in mind this needs to be at least a 8 gallon pot for a 5 gallon brew recipe.  The mashing/lautering process will extract about 6-7 gallons of wort that will be used during the boil.  Purchasing a turkey fryer(7 gallon pot with burner) for this is highly recommended and works well.

Steps to Mashing

1. Heating the Mash Water
2. Preheat the Mash Tun
3. Mashing
4. Heat Sparge Water

Heating the Mash Water

I recommend using filtered water for your mashing and lautering, check out building a water filter for brewing.  To get started, use the calculation below to get the amount of water needed for the mash.

(Pounds of Grains) x (Grist-to-Water Ratio)  /  4  = Mash Water Volume in Gallons

I usually start out with a grist-to-water ratio of 1.25-1.5 quarts per pound depending on the recipe.  Having a grist-to-water ratio higher then 2 is considered a thin mash and can lead to slower starch conversion.  Having a grist-to-water ratio lower than 1.25 is considered a thick mash and can lead to a sweeter maltier beer.  As a general guideline always heat up more water than you will use, go ahead and fill up 2 quarts of water per pound of grain.

heating up mash/sparge water

heating up mash/sparge water

Determine what temperature you should heat the mash water by finding out what your strike temperature should be.  For a grist-to-water ration of 1.25-1.5 the strike temperature is usually 10 degrees warmer then the desired mash temperature.  All of the all grain homebrew recipes I have included on BrewMoreBeer have their mash and strike temperatures described.

As a general guideline beers with more than 20% flaked barley, oats, rye or wheat can really benefit from what is called a protein rest between 95-113 degrees.  This topic will be written on more in depth in the coming months.

Preheat the Mash Tun

This step helps with initial heat loss to the mash.  To do this pour about a gallon or two of boiling water into the mash tun and swirl it around for a minute then pour it into your sparge water pot for recycling.

preheating mash tun

preheating mash tun


Mashing usually takes about an hour, refer to the mash schedule on your beers specific recipe for exact details.  As a general rule when mashing, you want to add the water to the grains and not the grains to the water.  Start off by pouring your milled grains into your mash tun, you can get your grains milled at your local brew store, by using a rolling pin, or buy purchasing a maltmill.  I use the Barley Crusher (15 lbs hopper) with a drill to mill my malt, the Barley Crusher does a great job.  Milled grains usually last about a week or two if kept in a cool dark place(airtight as possible). 

adding grains to mash tun

adding grains to mash tun

Add your mash strike water(can get temperature from recipe section) with a bowl or small pot and pour it over your grain bed.  Continue until you have achieved your desired grist-to-water ratio.  Stir the mash thoroughly and shut the lid. 

adding strike temp water to mash

adding strike temp water to mash

Wait about 15 minutes and check the mash to make sure it is at the desired mash temperature.  If too hot, leave the top open for a few minutes and stir, if too cold then you may want to add some boiling water to bring the temperature back up.  If the temperature of the mash is above 158 or below 140 it can cause bad starch conversion and will decrease the fermentablity of the wort.

Hopefully you still have a few cold brews left over from the last batch.  Now is the time  if you do to go and grab one, crack it open and relax for a few minutes.  After 30 minutes have passed you want to go and stir up the mash a bit.  At this time also make sure the temperature is still at or really close(within 2-3 degrees) to that of the desired mash temperature.  If not then adjust as mentioned above. 

stirring the mash

stirring the mash

When about 15 minutes remain in the mash began on the next step, Heating up the Sparge Water.

Heating up the Sparge Water

Heat up the necessary sparge water in the smaller of your two boil pots.  Here you will want to heat up about 3.5 to 4 gallons of water to about 165-175 degrees based on the specific 5 gallon recipe.  The sparge water amount is usually equal to about 1.5x the amount of water used for the mash.  The water will be added to the grains after the initial wort is drained off. 

After the mash is complete continue to the next article All Grain Brewing — Lautering to find out more on the process of getting the wort out of the mash.  Feel free to post questions/comments below.