Mash tun and boiler in one.I have been brewing all grain for a few years now and have managed to produce all manner of beers with my simple, low tech system. It involves mashing and boiling in an electrim bin and has elements in common with the “brew in a bag” system recently pioneered by Australian brewers, but it differs in a couple of ways, most notably the fact that I sparge and I collect the runoff in a second vessel before returning it to the boiler.

I have learned a lot about brewing since I started using this system and have spent quite a bit of money on equipment for various bits of my process, but I have never upgraded the mashing side of things. There are several reasons for this, like the fact that I get quite good efficiency numbers, but more importantly, I make good beer with this system and that is the whole point of brewing, after all. 


The best way for me to explain the exact nature of my system would be to take you through a brew day and explain it as I go.

Boiler Here we have an Electrim boiler, which is just a polypropylene bucket with an electric element in it. I have removed the thermostat from mine, as I found it to be useless, adding nothing but a point of failure to the system. I plug the element directly into a kettle lead and unplug it when I want to turn it off. You will notice that I have insulated the boiler. This insulation consists of several layers of thin Styrofoam roll interspersed with several layers of Radflect insulating roll. I used these materials for no other reason than the fact that I had them around the house. They are held in place with duct tape.

I have a copper hop strainer fitted to the inside of the spigot. I tend to leave this in place during the mash, as it does no harm and if I remove it, I might forget to put it back before starting the boil.

Wet is better MuslinTo turn this boiler into a mash tun I use a 1 metre piece of muslin cloth and two bungee cords. With the water heating to strike temperature, I drape the muslin sheet over the mouth of the boiler and carefully push it down, creating a bag for the grain. I then strap the edge of the muslin to the rim of the boiler with the bungee cords , to keep it suspended in the bucket. I find that it works best when wet, as the cloth sticks to the side of the boiler, so I splash the heating water onto the dry bits of muslin.

I tend to use roughly 3 litres of water to a kilo of grain, but I have long since stopped actually measuring it. I just half fill the boiler, more or less, depending on the grist, and set it on to heat. Even with a small grist, for something like a low gravity bitter or a mild, you have to use at least about 12 litres of water, otherwise the grain, suspended as it is in muslin cloth, and the rest of the liquor, might part company, as the grain absorbs water and lowers the level of liuid.

Grist Here is my grist, weighed out and ready to go. It is pictured in a plastic bag which is inside an old plastic fermentor. I find that this system works best when the grist doesn’t exceed about 5.5kg; any more than that and I start to see a fairly sharp drop in efficiency. In this case it’s 4.7kg.

MixingI have added various salts to the grist to adjust my water chemistry and get my mash pH where I want it. I won’t address water chemistry here, as that is a topic worthy of an article in itself. If you know how to use salts and acids to adjust your water, do so as normal. If not, consider using pH 5.2 Mash Stabiliser. When I have the water at strike temperature, I pour in the grist and mix it around to get it uniformly wet.

At this point, it is usually necessary to fine tune the position of the muslin sheet by pulling little bits of it from under the bungee cords, to maximise the amount of space available to the grist, in the bucket.

Temperature Check Now I check the mash temperature, adjust with cold or hot water if necessary, then pop the lid on and leave to rest. In this case I have the mash at about 67°C, which is where I want it. Anywhere from about 62 to just over 70 is fine, but lower temperatures will make a more fermentable wort, resulting in a dryer beer, while higher ones will make a less fermentable, more dextrinous wort, resulting is a more full bodied beer.

pH Here I am checking the pH of the mash. I use a pH meter to check a sample which has been cooled to 20°C. At this temperature the pH we are looking for is 5.4 – 5.8 so we’re fine.

At this point I feel I should issue a warning. Some of you may already be thinking, “Hang on; there’s an electric element in that mash tun. Why not use it to raise the temperature, if you need to? You could even step mash with that.” But no, don’t do that. That electric element is sitting in starch filled water and switching it on at this point will result in burnt starch coating the element. This causes the element to overheat and cut out during the boil. The burnt on starch is a bugger to get off too. Does it sound like I found this out the hard way?

 While the mash is resting for about 60 minutes, I clean the kitchen, make lunch and heat my sparge water, on the hob, in a large stock pot. This one holds about 15 litres to the brim, so I use it to heat two additions of about 12 litres of water to 80°C. 

After the mash is finished, I begin to recirculate some of the wort. I use a 3 litre plastic jug and simply drain wort from the spigot and pour it gently onto the mash bed , to clear it. I usually recirculate about 10 litres of wort before I get bored. 

Drain Next I drain the mash tun into a plastic fermentor and set it aside. Note the plastic hose I have attached to the spigot. This is to reduce splashing and minimise oxygen uptake while the wort is hot.  

80°C water goes into the mash tun and I stir it up to get those sugars dissolving. As soon as I have it stirred up, I get the stockpot heating again. To reduce the time it takes to heat the next sparge addition, I only put about 6 litres of water on to heat in the pot and I boil the kitchen kettle several times, adding the boiling water to the stock pot until there is about 12 litres of water in it. The water is usually in the high 70’s by the time I add the last kettle of water. 

While waiting for the kettle to boil I recirculate wort through the grain again, to clear the wort, then drain the mash tun into the plastic fermentor. 

Sparge Sparge with the last pot of 80°C water, recirculate and drain, but wait! There’s too much wort! The plastic fermentor will not hold all of the wort generated by the last sparge. This is where I put about 8 litres of wort into the stock pot and set it aside in the kitchen. You see I have never been particularly happy with the size of my electrim boiler anyway. I find it’s just a little bit too small for a full wort boil that is to end up with 23 litres of wort, after evaporation and wort absorption by hops, so I boil 8 litres of wort separately on the stove and add it back to the main wort about 15 minutes from the end of the boil, when evaporation has made some room. 

Spent grain Now it’s time to clean out the mash tun so we can use it as a boiler. The muslin makes this very easy, as all I have to do is remove the bungee cords, pull out the muslin and dump it into plastic bag that was my grist case. 

Now I hose out the boiler, check that the hop strainer is secure and siphon the wort across from the fermentor. While this is happening, I remove the muslin sheet, leaving the grain behind in the plastic bag. I clear the worst of the grain off it with my hand, then hose it down a bit and shake it out. I find that these sheets can be used about four times before they get a bit tatty and need to be replaced. 

HopsFrom here on it’s pretty much the same as any other full boil method. I bring the wort to the boil, wait for the hot break, then add my bittering hops, at the start of the 60 minute countdown. In this case the only other hop addition was at 20 minutes. 

While the wort is boiling I fill the fermentor with sanitiser and use it to soak the hydrometer, trial jar, etc. 

 At the end of the boil I plonk my clean but mangled looking immersion chiller into the wort to sanitise, then chill the wort and run it off into the now drained, sanitised fermentor and pitch the yeast.

Home at last Here is the wort, finally at rest in my thermostatically controlled fridge. The wire you see leads from a probe in a stainless steel thermowell, dipping into the beer, to an ATC-800 temperature controller, which has control of the fridge. This system keeps the temperature of the fermenting beer within 1°C of what I set.

I hope that this article has demonstrated that you don’t need a high tech system to make all grain beer. There are certainly disadvantages to this system, there is a lot of transferring of wort, for instance, but it has its advantages too.

A variation of this system, one which I will probably try fairly soon, would be to insulate a plastic bucket fermentor (one with a tap at the bottom, naturally) and use it as a mash tun, instead of the boiler. This would mean that you could run off directly into the boiler, without the intermediary step of transferring to a fermentor.

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