MY MAGIC MASH TUN

by Graham Sanders

To me your mash tun is one of the most critical pieces of equipment. Its design will determine many important factors if you decide to mash with grain. A poorly designed mash tun will increase your brew day, create far more work, will affect the flavour of your beer, cost more in grain to buy and even can put you off getting into all grain brewing for life.

Now there are many designs out there, and all have their advantages and disadvantages. Many people personally ask me how I get great efficiency out of my mashes and my mash tun design does help significantly. Now I have what they call a HERMS (Heat Exchange Return Mash System), and my mash tun was designed for that, but my first priority was wanting a stainless steel mash tun. I wanted that for ease of cleaning and I wanted it to last a lifetime.

This is my mashtun set up ready to use.

This is a 50 litre keg that I was able to get surplus due to a damaged top.

There are two types of 50 litre kegs in Australia at the moment, the fatter CUB type kegs and the taller, and narrower Lion Nathan kegs. The taller types kegs are the go here, as you want a decent depth in your grain bed, and these narrower kegs allow this.

A normal grain bill for a 38 litre beer (say 8 kilograms) will fill this keg about half way, while a typical bock grain bill (9 to 11 kilograms) will only fill it ¾ full. So it has all the capacity one would need for the average CraftBrewer.

So let's look into it in more detail.

First the base of the tun.

You will notice I have not modified the basic shape of the keg. That remains unchanged. I want to take advantage of the natural dish shape at the bottom. Now you do need the help of a good TIG / MIG welder for the next step. I have attached a stainless steel pipe right at the bottom and running out to the side of the rim. That way the keg can still sit on the ground. I attached a threaded blank to the end of the pipe.

You could attach a tap to this if you wish, but because I use a pump I have attached a special fitting so it can be connected to the pump. (visible in the previous picture, or refer to the article on A Perfect Pump).

So what is the advantage of this setup. Well I am drawing liquid from the lowest point in the tun. This creates a consistent flow right through the system. But the main advantage is the simple design of the filter screen.

Let's have a look.

In this picture the screen is standing on its edge. It is woven stainless steel, cut in a circle roughly the diameter of the keg.

The grade is thick so it's quite stiff. During use I place a stainless steel spring under the centre of it to ensure it stays off the bottom.

So how do I get a good fit. This is where you use the concave base to its advantage.

This is the screen in place. Because of the concave bottom, the screen will naturally form a tight fit at the bottom of the keg. If you look carefully, you can see the drain hole in the bottom as well.

Now many will wonder how I stop the grain falling through the screen. Well a layer of rice hulls about 30 centimetres deep does a nice job, as well as allowing the grain bed to drain uniformly without any resistance.

Finally the top. Again nothing special here.

You can see the small size of the opening here. I had three requirements.

1. The opening needed to be as small as possible to trap as much heat as possible.
2. It had to big enough to do decoction mashes and the pipes for my HERMS
3. I had to be able to get the screen in and out when I needed to do so.

Now this is the final shape I came up with. The pot can get into the tun, with the pipes in place. The groove through the top allows the screen to be removed and replaced without bending it. Also note I had to put a groove in the rim(next to the pipes) to get the screen in.

So that's it. The design is very simple, plus its easy to make and easy to clean. And it works great.

Shout
Graham Sanders