We are beginning a multi-part series on mash tun design. If you are moving into all-grain brewing, one of the most important pieces of equipment you will be adding is a mash tun. There are a lot of considerations that go into the design of a mash tun, so I have asked Raleigh home brewer and local mash-tun expert, John Szymankiewicz to put together this multi-part series on picking out and/or building a mash tun.
The first part of the series focuses on the actual physical mash tun – what the container is made of, as well as it’s size and shape. In the upcoming posts, John will share his insights into the draining of the wort out of the mash tun, the sparging process, and different ways to heat your mash.
If you wanna brew all-grain, you’re gonna need a mash tun.
Mash tuns can range from simple and cheap to costly and complex, you need to find the one that works best for you. This post will review a few of the basic equipment considerations you need to think about when choosing, designing, or building a mash tun for your home brewery.
What is a mash tun?
A mash tun is nothing more than a big container where you can mix your grain and water and let the natural enzymes do their magic (with a little help from modern chemistry in some cases) and turn your starchy grain into sugary wonderfulness. Because it’s nothing – really – more than a container, almost anything can be used as a mash tun. Some brewers will use their boil kettle (such as the brew-in-a-bag method), a bucket (see Charlie Papazian’s Complete Joy of Homebrewing), or a cooler (google Denny Conn’s batch sparging method). The complexity of mash tuns comes from two aspects: lautering and temperature control. We’ll discuss temperature control and lautering in different posts. Right now I want to focus on the container itself.
Your tun can be made of almost anything. But, it has to meet two conditions: (1) it must be food-safe (meaning that it isn’t going to contaminate whatever you put in it), and (2) it should withstand temperatures of up to about 170°F (77°C). If you do it at all, 170°F (77°C) is where’re you’ll want to “mash-out” (that is, denature or stop the enzyme activity) at the end of the mash. To be safe, because I may want to do a decoction mash at some point, I might want my tun to be able to handle up to 212°F (100°C) in small amounts or very short periods of time. So here’re some thoughts on the materials:
Steel / Stainless Steel
This should really be “metal” overall, but there just aren’t that many copper, nickel, or cast iron pots that people use for mash tuns. The most popular metal choices are steel and stainless steel. Here’s the thing, your mash is going to be slightly to moderately acidic, that can cause corrosion issues over time. When thinking about corrosion, don’t just think rust and structural things, think also about – “if that’s stuff is going away, where’s it going? IN MY BEER!” So, you probably want something that’s going to hold up well over time.
Professional breweries have long used stainless steel and it’s a good choice. Steel can also work, but cleaning is a little bit more difficult – worrying about rust, etc each time you use it. Copper is a good choice – but expensive (more than the stainless option at the volumes you’ll need). Oh, I should also mention aluminum as well. Aluminum is not my first choice for materials, though it could do in a pinch. Aluminum really dislikes acidic conditions and will corrode quite quickly.
Copper and Aluminum are easy to work with, but… well, the good news is that they’re fairly soft metals… the bad news is that they’re fairly soft metals. Being softer metals, they’re easy to work with, but also easy to damage.
Speaking of easy to damage… consider a porcelain or enamel coated pot. These are long lasting and inexpensive. The downsides are that they’re hard to work with (try drilling a hole in one, as an example), and the coating can easily be chipped. Once the coating is chipped or otherwise breached, the bare under-metal is exposed and can often corrode quickly.
Overall, stainless steel though it is harder to work with, is my choice for a metal mash tun.
Plastic is a touchy subject. Plastics can be inexpensive and come in a variety of configurations. They’re resilient, light, and easy to work with. The downside is that many can’t hold up to the temperatures you’re looking at.
Most High Density Polyethylene (HDPE – look at the bottom of the container, it’ll have a code) will hold up just fine to higher temperatures (up to mash out temperatures) for a sustained period, for example, until it cools off (on the scale of a few hours). Another plastic you’ll see quite a bit is Polytetrafluoroethylene (PTFE), popular for thin-walled applications like soda bottles. PTFE is a particularly bad choice for temperatures we’re looking at. Certain PTFE formulations do better than others, but for must consumer plastics – generally, they’ll start to break down and leach polymers at over 150°F (65°C). You’ll also see polycarbonate (PC) available in some cases. PC seems to hold up fairly well, but tends to get much more… flexible at warmer temperatures.
If you’re looking at going with a plastic tun, I’d choose HDPE or some variant or copolymer of it. Be aware that some items, like a cooler, will have an exterior shell or an interior coating/sleeve these may be of different materials. Despite statement, I’ve had very good luck with coolers. They tend to fairly durable, cheap, and (as a bonus) hold temperature well.
You need to think about what size tun you’re going to need. Size requirements are going to depend on a few factors: (1) how big of a batch are you making? (2) How much grain are you going to use, and (3) how thin or thick will the mash be? As you can probably guess, these all play off each other. Mash tun not big enough for all the grain? Make a smaller batch – needs less room in the tun. Mash too thick to stir or lauter? Thin it out with some additional water – needs more room. For reference, a standard “mash thickness” is about a 1:1 ratio, 1 quart of water per 1 pound of grain. I tend to run a thinner mash for other processing reasons, about 1.25:1. In my mash tun, 18lbs of grain (with the appropriate amount of water) takes up close to 9.5 gal of volume. Another reference ground barley is about 25 lbs/ft^3 (~ 3.3 lbs/gal) + the water you’re adding. Let’s say you’re doing an all-grain dopplebock with 23 lbs of grain. That’s roughly 7 gals worth of grain + ~9 gal of water, with my ratio. That means you’d need a 16 gal mash tun and it’d be filled to the very-tippy-top!
If you’re looking at using a bucket, they come in some standard sizes: 5 gal, 7, gal, etc. Pick one that makes sense. If you’re using a cooler, they come in an almost infinite number of sizes. Remember that 4 qts = 1 gal. You can also look at geometry with a cooler. There are square, rectangle, and cylindrical styles available. In stainless a popular choice is the keggle (converted keg = the top is cut out) at 13.5 gal. Otherwise, look to a pot in the 20+ (5 gal) quart range, 30 or 40 quart pots are also an option. The coolers are nice because many already have a port at the bottom and hold temperature really well.
Configuration and Recommendation
5 gal Cylindrical Cooler
- Holds temp really well
- Relatively easy to clean (dump -> hose out -> wipe -> rinse)
- Available almost everywhere
- Holds temp well
- Too small for any 10 gal batch (except maybe a session mild) and too small for a 5 gal batch of high gravity beer
- DIY total cost: ~$75 (cooler + bulkhead kit + ball valve)
- 5 gallon cooler with bulkhead, ball valve and false bottom
- Expensive to purchase legally
- Looses a good deal of heat, the only thing working in our favor is the thermal mass of the grain
- Clean up is a breeze and I don’t have to worry about scratching the surface (not a huge deal in the mash tun, but still)
- Hard to find (legally), unless you get to be good friends with your local brewery (Remember kids: don’t steal kegs!)
- Great volume, room enough for 10 gallons of a high gravity beer
- DIY total cost: ~$150-200 (keg + effort to cut out the top + bulkhead kit + ball valve)
- Ultimate Mash Tun Keggle
10 gal Cylindrical Cooler
- Holds temp really well
- Relatively easy to clean (dump -> hose out -> wipe -> rinse)
- With a tall grain bed (i.e. because it’s cylindrical), I’m less concerned about the water channeling through the grain bed and not rinsing everything
- Good volume for enough grain for 5 gallons of dopplebock, imperial IPA, or barleywine
- DIY total cost: ~$75 (cooler + bulkhead kit + ball valve + false bottom)
- 10 gallon mash tun with stainless false bottom or 10 gallon mash tun
When I first started my mash tun adventure, I was really enamored of stainless and big beers. Since then I’ve realized I can’t drink 5 or 6 pints of dopplebock everyday and I’m trying to make my life more simple – not more complex. So, I’m running a 10 gal cylindrical cooler and love it. Sure it’s not as flashy and shiny as the stainless (after you brew on it a few dozen times and it gets “character” it does start to look a little ghetto), but it’s cheap, dead easy to use, and easily replaceable.
For the newbie – I’d recommend a 10 gallon cooler any day. They’re cheap and real workhorses. If you wanna feel more “brewer-y,” go ahead and go for the pot/kettle/keggle mash tun with the shiny stainless, but it’s more work.
In our next post, we’ll talk about maintaining temperature, step mashes, and lautering.
In the meantime, here’re some resources regarding mash tuns:
- Batch Sparging with Denny Conn
- Cheap ‘n’ Easy Batch Sparge Brewing (Denny Conn)
- Brew in a Bag
- Mash Efficiency
- Metals that Affect Your Beer