Partial Mash Brewing Guide

The image above of the cooling down of a partial mash boil in the kitchen sink full of ice likely brings back fond (or frustrating) memories for brewers of when they first got started.

Why Partial Mash?

Most brewers are introduced to the hobby by wandering into a local home brew shop and getting a starter equipment kit (normally under $100 USD depending on what's included), and an extract recipe kit to use with that equipment.  The most basic of the kits are cans of pre-hopped liquid malt extract with an extra bit of fermentables in the form of dry malt extract.  These are very easy to use (basically sanitize everything and mix with warm water then pitch the yeast) and generally produce a drinkable product for very little effort.

On the other end of the spectrum are the all grain brewers that perform a mash on malted barley and convert their own sugars to a fermentable state. Boil the full volume of wort, design recipes in software to style guidelines, and all sort of other things that require an incredible amount of effort compared to the extract kits.

Somewhere in the middle of these two is the partial mash brew.  Originally I viewed it as a step between the simple extract kits and the full commitment to all grain that was simply another step in the process.  I personally only did around six partial mash brews (and only two extract brews before that) before jumping to all grain.

Recently however several friends have shown interest in the hobby but don't quite want the full commitment of purchasing the equipment and keeping up with the details for an all-grain brew day (around 7-8 hours for my setup).  So they would try a simple extract kit from the local shop with the plastic bucket economy equipment kit.  Sure enough they loved having their own beer to drink at home but wanted more control over the process/beer that wasn't offered in extract kit form factor.

This is where the partial mash shines, great control over the process (relative to extract), wider selection of styles, low equipment costs, and a much shorter time commitment for each batch.  With the addition of a small amount of specialty grain to the extracts that contain many of the fermentable sugars you can achieve the body and depth that's often missing from extract only brews.I am actually a very big fan of the partial mash process now for the casual brewer. Not everyone needs a miniature commercial brewery in their basement, and truth be told you can make incredibly good beer with the process.  The guide below lays out the general process of completing a partial mash kit I purchased for this post.

More after the Jump




Equipment Overview:
Most of what I used to brew the kit comes in a standard beginner kit.  One of the main things that's usually not included in the basic kits is a kettle, if you already have a pot in the 20-24 Quart range you're covered.  If not expect to pay around $30.00-$40.00 USD for a kettle in stainless or a little less for aluminum.  Outside of that the things your kit will need are:

-Mesh bags to put your grain in for the partial mash
-Thermometer - the more accurate the better since brewing is all about temperature control and timing
-A kitchen timer - you don't want to be watching the clock (use your phone if it has one built in)
-Plastic Bucket fermenter with a lid that seals well
-An Airlock for the lid to let CO2 escape during fermentation without letting air back in
-Sanitizer to get everything clean - I prefer the no rinse ones
-A hydrometer to take gravity readings (and a wine thief to pull the sample)
-A plastic bucket with a spigot for bottling
-About 5ft of vinyl tubing to transfer the beer
-A bottle capper (unless you're kegging)
-Bottles and Caps (you can reuse any bottle that has pry off tops)


Optional Items
-Auto-siphon - this is only optional because you can get by without but I very highly recommend it, I think of the auto-siphon as the best $10 I ever spent for a piece of brewing equipment.
-Funnel with a screen - use this when transferring into the fermenter, helps with aeration and catching any hop particles that didn't settle out very well.

The Whole Kit Spread out on the Counter

Ingredients Overview: 

I purchased an English Pale kit from MoreBeer, (you can see their logo in the picture above).  The kit included a bag of liquid malt extract (metallic upper right in the picture), two hop additions (the smaller metallic bags), a packet of dry yeast (S-04 English Ale which is the blue packet), bottling sugar (white powder in the upper left), and the grains for the partial mash (bottom left).  The grains must be milled so that water can get into the sugars the malter worked so hard get from the raw barley.  Some kits offer the option of sending un-milled grains so be sure to check that yours are milled unless you have a mill.  The ingredients list in the bottom right that came with the kit also listed some expected gravity ranges that you should achieve when brewing.

Overall most kits should have similar ingredients and may use dry malt extract instead of the liquid.  One of the main things to look for in these kits is fresh ingredients as age can affect flavor.  These things have a shelf life measured in months so it's not like it's fresh vegetables just try to make sure you're not getting past a year.  
Don't worry about making your own recipes the first few times, learning the process with a tested kit will help your brewing way more early on.  It's also easier to trouble shoot any issues to the process rather than the recipe. 

Preparing Water and the Mash:

Kettle with the Mash Water 

The very first thing you'll want to do is measure out your water for the partial mash, this will be around 2-3 gallons.  Leave some room in your kettle since boil overs (we'll touch on these later) are a real mess to clean up.  You'll likely be using either spring water from the store or tap water.  If you're using tap water and haven't filtered it first there will be chlorine in it.  To get rid of the chlorine you can bring it up to a boil for a couple of minutes and cut the heat to let it come back down to temperature.  If you're using spring water you'll just need to bring it up to temperature.  Don't use distilled water since the minerals in the spring/tap water help with the mashing process.  The temperature we're shooting for is 170° F, anything above this temperature could result in tannin extraction from the grain that will create off flavors in your beer.  



While the water is warming up go ahead and place the milled grains in the mesh strainer bag and loosely tie the top.  Most bags have draw strings to close them up just be sure you can get it untied later.

Grain in the Mesh Bag

When the grains are ready to go check your water temperature to be sure you're at 170°F or just a little below.  Now it's time to start the mash.  With the water at temp and the heat off dunk the bag a few times in and out of the water to make sure everything is soaked well.  You can agitate the bag with a spoon a little to help this along.  Once that's done the water should have cooled a bit to the mid to high 160°F's since the grain we just added was room temperature.

Just after placing the grains in the mash water, notice the color change has already started.

Now place the lid on your kettle and set the timer for 30 minutes. I like to keep the top of the bag pinched between the lid and the kettle for easy removal later, no fishing around in hot water for the bag.  During this time some enzymes in the grains will convert some of the sugars to a fermentable sugar that the yeast can use.  This will depend on the grain you have as some have no power to convert themselves (this is called diastatic power if you want to know more).  You'll also get great color and flavor from the specialty grains that you just can't find in malt extracts.

After the 30 minutes is up pull the grain out and let the bag drain into the kettle.  Don't squeeze out every last drop as that can also extract the tannins we mentioned above, just let it drain naturally for a few minutes.  What was mash water is now called wort  (un-fermented beer), although with a very small amount of sugars.

Draining the grain bag, notice the darker color compared to the beginning of the mash

Now go ahead and turn up the heat to start bringing the wort to a boil.  While the wort is warm but not quite boiling is a good time to add the extracts that will boost the sugar content up to that of a normal beer (actually around double that of a normal beer since we're only around 2-3 gallons of the 5 gallons we'll have at the end).

We'll be using liquid malt extract from a bag that came with the kit.  If you're using cans of liquid extract you'll want to put them in a bowl of warm water to help them pour a little better.  With the bags you can roll it like a toothpaste tube after you pour most of it in the kettle.  Dry malt extract is also fine for this step and some kits will use it instead of the liquid.

Pouring the Liquid Malt Extract into the Kettle

As you're pouring your extract in be sure to stir like crazy.  It's heavier than the wort and will settle onto the bottom and burn if it's not mixed in well.  After it's all mixed in stay with the kettle as it heats to a boil.  You'll be there for a couple of reasons.

First watch for the hot break.  A frothy surface will build up on the top of the wort before it comes to a boil, this is the hot break and is made up of proteins from the malted barley and extract (which is also malted barley).  

Hot Break

Second, when the boil starts you'll want to be sure to adjust the heat to avoid a boil-over.  The sugars will really froth up and can over run the top of the kettle.  Thick sugar water smokes a lot when it hit's a stove eye, and is really a mess to clean up anywhere else it gets.  From this point until the boil is finished don't place a lid on the kettle, you want some chemical compounds to be able to escape with the steam to avoid off flavors.  They're nothing that will hurt you just things that will cause off-flavors.  The primary compound of concern is DMS (dimethyl sulfide) which causes a flavor similar to cooked corn.  It's not as big a deal in a partial mash but why take any chances of an off flavor. 

Third you need to start the timer at the start of the boil so hop additions can be correctly timed. 

The Boil and Hop Additions:

Most boils for the partial mash method will be 60 minutes total and usually have a hop addition right at the beginning.  This is called a 60 minute addition and it goes in with 60 minutes left in the boil, not 60 minutes into the boil.  The amount of time hops spend in the boil creates different types and amounts of bitterness.  The longer the hops are in there the more bitterness and less aroma you'll perceive when drinking the beer later, the opposite is true for later additions (less time = more aroma).   

Late (5 minute) Hop Addition and Whirlfloc Tablet

Simply watch the clock and dump in your hops at the prescribed times in the kit instructions.  Towards the end of the boil you may use a flocculation agent (Irish moss, whirlfloc, etc.) which will help bind some of the floating hop bits and proteins from the break materiel so they settle out better.  A word of warning watch the kettle closely with a spoon in hand when adding hops, the addition makes the boil rise up very quickly and we've already been over how much a boil over can suck. 

To help with getting the hops out of the wort at the end of the boil I like to use a large mesh bag that fits over the lip of the kettle.  When the boil is over just pull it out and let it drain back into the kettle for a bit and place in a bowl.  It won't get everything but it does cut down on the amount of hops that make it into the fermenter.

Hop bag and hops pulled out after the boil

Chilling and Transferring:

From this point forward everything the wort touches must be sanitized.  Before this point it really didn't matter since the boil would kill anything that got into the kettle.  The goal here is to minimize the amount of things that can float into the wort.  If you have a ceiling fan going in the room turn it off well before the end of the boil so the air can settle.  Step number one after the hop bag comes out of the kettle is to spray a lid for the pot with no rinse sanitizer and get it on the kettle before you move it to an ice bath.

To prep the ice bath (you could do this during the last few minutes of the boil) place a stopper in your kitchen sink, fill with ice (I use the entire ice-maker bin from my freezer), and run in some cold water (heat transfers better into water than air).  Make sure the pot will fit in your sink before you even start brewing or you'll need to do something else.  Also leave some room for the volume of the pot in the sink.  The first time I did this I filled the sink nearly to the top and when I plunged the kettle in water went everywhere.  Then take your pot (lid still on) and place it in the ice bath.

Yeah it's just a different angle of the first shot

Let it cool while you start sanitizing the fermenter and siphon equipment.  I like Star-San since it's no rinse, easy to mix, and quick but any sanitizer sold in your home-brew shop will work.  Just follow the directions on the bottle to sanitize anything the wort will touch and you'll be fine.  I like to sanitize the lid of the bucket and keep it loosely on top while I'm sanitizing the other equipment.

Loading the Fermenter with Top Up Water

Once everything is sanitized go ahead and pour a gallon or two of top up water in the fermenter.  This does two things, first and foremost it will bring your batch up to final size.  Leave a little space though since you will have lost some amount of volume to boil off in the form of steam, we'll top up the last half gallon at the end.  Second the wort will still be a little warmer than pitching temp unless you had a very good ice bath and this will help cool it further.  You can keep this water in the fridge so that it's really cool if you have doubts about how effective your ice bath will be.  Basically if you had two gallons at 40° and two gallons at 100° the would equalize out to 70°. You can do the math as ((V1*T1)+(V2*T2))/(V1+V2)=T3 where V = volume and T = temperature, or you could just by a fermometer to put on the outside of the fermenter (it's like a fish tank thermometer sticker).

Auto-Siphon in action

Now it's time to put the wort in the fermenter.  Simply give an auto siphon a few pumps and let gravity do the rest.  Hold the other end of the tube above the water level in the fermenter so you get a little slashing action to help oxygenate the wort.  All the O2 was driven out of the wort during the boil and the yeast you'll pitch in a few minutes will need some oxygen to be all they can be.  When I do this I run it through a funnel that has a screen insert to catch any little hop particles that the bag may have missed.

Running Wort into the Fermenter through the Funnel/Screen

Once you have everything in the fermenter check the volume and top up to 5 gallons if you aren't already there.  Use a sanitized wine thief to pull a sample and check the gravity with your hydrometer.  Check the temperature with your sanitized brewing thermometer (or the fermometer on the side of the bucket we mentioned above) to be sure it's in range for the hydrometer you're using.  Put the sanitized lid back on loosely and get ready to pitch the yeast.

Pitching the Yeast and Fermentation:

Most kits come with dry yeast packets that are intended to be either re-hydrated or sprinkled directly into the wort.  Follow the instructions on the packet, if the packet has no instructions buy better yeast.  Yeast is a subject all it's own that really affects the outcome of the final product.  While we won't get into a full discussion on yeast here I will say this:

-Be sure you pitch the yeast into wort that is in the same temperature range as the fermentation range listed on the packet.
-Keep light off the beer during fermentation, if using something clear put a t-shirt on it.
-Ambient temperature in the room is not the temperature of the fermentation, aim for a room temp at the low end of the listed fermentation range, expect the actual fermentation temp to be 3°F-7°F warmer.
-Keep it in a place with a stable temperature, you do not want temperature that swings up in the middle of the day and cools at night.

Preparing to Pitch the Yeast, note the foam on top from the "splashing" aeration during transfer.

That said my packet said to sprinkle directly into cooled wort so that's what I did for the sake of following instructions for the kit.  Dip the top of the packet in sanitizer, sanitize some kitchen scissors, cut the top off the packet and sprinkle.  Currently I'm usually a liquid yeast guy simply because I have the equipment.  Early on I used dry yeast for 80-90% of my brews, they are easy and turn out great results.

Yeast is Pitched

Now get the sanitized lid sealed up tight with the sanitized airlock in place (don't forget to add liquid to the airlock) and move the fermenter to the location you have picked out that meets the criteria listed at the beginning of this section.  Wait a couple of weeks (or even better check the gravity after a week then every few days to be sure the yeast is done) and it's on to bottling.

Ready to Go Away for a Couple of Weeks

Bottling and Conditioning:

We've previously done a post on bottling on the blog and as it's really a separate process (an this is gotten way longer than I intended)  I'll reference you there.

Our Post on Bottling

Please let me know if a step wasn't clear (or more likely where I screwed up) in the comments to help us out.