Introduction
A while ago, I was rather taken aback when one of my local homebrew club’s leading lights (OK, it was the Naughty Nurse) showed an interest in my beer brewing techniques – especially in the way I mashed grains. I understand that he has since taken this information and not only built his own mash tun using my approach but has also convinced others of its merit too.
Actually, I cannot claim to have developed this myself. There are several websites describing in brief detail how to do this. I just did the same because I thought that’s what everyone did anyway. For this project, I’ll put my own perspective on this device and provide a much more detailed explanation on how to build this type of mash tun. Instructions on how to use it to best effect are given HERE.
The three main components to construct the mash tun are:
- Beverage cooler
- Spigot assembly
- Stainless steel braiding
The full list of parts is shown below.
Parts List
Choosing a Cooler
I’ve bought both a 5-gallon and a 10-gallon Rubbermaid beverage cooler from a local hardware store. Igloo is another brand that I’ve used in the past. These instructions can be applied to all of these. I typically brew 6-gallon batches of beer. The 5-gallon cooler will mash up to about 12-lbs of grain so this is ideal for most of my beers and costs about $20. The 10-gallon cooler costs about twice this amount and is good for mashes with up to about 24-lbs of grain. I would recommend that you get the 10-gallon cooler if you are making large or strong batches of beer otherwise your mash is going to be very messy. For even larger volumes, a bigger chest cooler with fancy wheels could be used – but make sure that it is fully sealed to take in hot liquids.
Most coolers come with a plastic spigot. On my first (Igloo) cooler, this could be partially opened by inserting a coin under the spigot lever. This was not very elegant, but it was cheap and effective. These Rubbermaid coolers have a push-button spigot which doesn’t work with coins.
It’s very important to control the flow of wort from the mash tun – too fast and it will reduce the effective sparging efficiency and possibly block up the grain bed and, if too slow, it will take forever and start to pull stuff you don’t want from the spent grain husks. So, it’s important to have a spigot that will allow control of this flow and not get blocked. A ½” stainless steel ball valve seemed to be ideal for this purpose.
The parts list above shows stainless steel components which will have a relatively high price (about $30 in total) – I purchased these because I had just been paid and stainless steel is the best choice for food safety, physical strength and resistance to corrosion. Similar assemblies could be put together for cheapskates using brass or even plastic parts. A really cheap and simple method would be to use a simple barbed adapter instead of the ball valve and put a compression (Hoffman) clamp on the flexible tubing that will be attached to this adapter. However, I think a ball valve is much more practical and less likely to leak.
Putting Together the Spigot Assembly
First, remove the plastic spigot that came fitted to the cooler. Check that the 1½” x ½” nipple will fit through the hole left after the original spigot has been removed. Drill out the hole if necessary.
Wrap PTFE tape around the threads on one end of the nipple and thread the nipple into the ball valve inlet to make a good seal as shown.
Slip one of the stainless steel washers over the nipple and push the other end of the nipple through the hole in the cooler as shown. In some instances, a rubber o-ring or rubber washer may have to be placed between the washer and the cooler to prevent leaks.
Slip a second washer onto the end of the nipple and secure the assembly in place with the recessed lock nut as shown. The nut recess should be away from the valve. Firmly tighten the nut with a suitable wrench but don’t over-tighten or you may break the walls of the cooler.
At this point it’s worth checking that the seal is leak tight. Pour some water into the cooler and check that there are no leaks and that the ball valve is able to drain the cooler.
Now fit the FPT barb onto the inside of the nipple as shown. This probably won’t seal well but that’s not important. Just make sure it’s tight enough not to fall off during use. No PTFE tape is needed.
Finally screw the MPT barb into the outlet of the ball valve as shown. PTFE tape should be used to get a good seal or else bubbles of air may form while draining the mash tun and cause possible hot-side oxidation.
Stainless Steel Braided Tubing
Stainless steel braided tubing is a simple alternative to the more established false-bottom device used in commercial mash tuns. It has a very fine filtering capacity, is relatively cheap (about $5) and doesn’t occupy much of the volume inside the cooler. The photo shows how fine the braiding is – it’s a great filter for a mash tun. I have found it to be much superior to the false-bottom approach.
Go to a hardware or plumber’s store and buy a faucet connecting hose with external stainless steel braiding. Don’t use plastic braiding. Get the longest one you can. I use one that is 24″ and another that is 48″ long. These connecting hoses can be obtained in longer lengths (several feet) for washing machines, etc. which will give even better performance. These long braided tubes are good for when a recipe calls for large amounts of cereal such as wheat, oats, corn etc.
Take a hacksaw and cut off the fittings at each end of the hose as shown . Throw these bits away – they are now totally useless. Pull (actually, it’s easier to push) off the braiding and throw away the polymer core (again totally useless). Watch your fingers during these steps – the wire in the braiding loves to stick into fingers, so wear thick gloves.
Crimp one end of the braiding with stainless steel wire or a staple as shown. I hammer on a piece cut from a stainless steel pipe clamp.
Push the other end of the braided tube onto the ½” barb on the inner end of the spigot assembly as shown . There is normally no need to secure it with a clamp—the barbs will keep the braiding in place but use a stainless steel pipe clamp if it makes you happy.
Arrange the braiding so that it won’t flail around during addition of water or stirring as shown. I loop it around and tuck it under the barb fitting. Use some stainless steel wire or plastic straps to secure the loop.
Pour some water into the cooler and make a final check for leaks. A leaking mash tun full of wort is an interesting dilemma to address (as I’ve learnt the hard way).
The mash tun is now ready for use.
Basic Mashing Technique
More interesting methods of mashing are given in another (yet to be included) section of this website. In the meantime, here are some guidelines on how to use your new mash tun for a basic mash.
I’m a cheapskate brewer so I like to maximize my mash efficiencies and I find that fly-sparging gives me the best efficiency and with this type of mash tun I often reach over 90% extraction.
Here’s my procedure to perform a simple mash…
- Check that the faucet on the mash tun is fully closed and that everything is leak-free. This is very difficult to fix during a mash.
- Prepare the grist as you would normally for your recipe.
- Pour the required volume of mash liquor (water) at the required temperature into the mash tun. I use BeerSmith software to calculate the volume and temperature of the liquor needed for my recipes.
- Pour and quickly stir the grist into the hot liquor in the mash tun. Break up any clumps of grain with a steel whisk.
- Check the temperature of the mixture and, if necessary, stir in small amounts of boiling or cold water to get it right. I hardly ever need to do this.
- Put the lid on the mash tun and leave things to mash for an hour or two.
- In the meantime, DON’T stir the mash. I don’t fully understand the mechanism, but this no-stir approach increases mash efficiency significantly and provides a very clear and fermentable wort.
- After the mash period is up, rest a Styrofoam plate on top of the grains in the mash tun. This is my cheapskate sparging device to prevent the grain bed, once set, from being disturbed.
- Slowly drain about a pint of wort from the valve and return it to the top of mash. The wort should run very clearly. Drain a bit more if necessary.
- Connect a length of high temperature tubing to the barbed outlet fitting on the valve. Put the other end of the tubing inside the empty boil kettle (inside the hop spider if you’re using one and want first wort hopping). This tubing provides two benefits: it keeps air away from the hot wort (stops hot-side oxidation) and the weight of the wort in the tubing will help pull the wort out of the mash tun (and prevent slow sparges).
- Adjust the valve to allow a slow flow of wort into the boil kettle.
- Each time the wort inside the mash tun drops below the the top of the grain bed, use a saucepan or some other suitable vessel, to scoop up the previously heated sparge water and pour it onto the Styrofoam plate.
- Keep adding sparge water to keep the liquid level in the mash tun just above the grain bed. Use a refractometer to periodically measure the Specific Gravity of the wort entering the boil kettle. Once this starts to approach about 1.010, stop adding any more sparge water and turn off the valve. It should take about 45 minutes to drain the wort from the mash tun into the boil kettle.
Final Thoughts
The total cost of all the parts was just over $50. This did require some chasing around to get the parts and the use of hacksaws and wrenches etc. Using a 10-gallon mash tun would cost about $20 more (for the bigger cooler).
I’ve being using both sizes of these mash tuns for several years and they have served me very well.
If you decide to build a mash tun like this and have good success, please share your experiences by sharing your comments below.
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