The plan: make a mash tun out of an esky. I’m not the first to do this by any means, but everyone seems to do it slightly differently and the biggest part of the challenge is working out how you’ll do it and where on earth to get the bits (cheaply, of course!)
First up I need an esky. So, again it was a quick browse on Gumtree. There I found a pretty much brand new Coleman 40L esky for sale by some Skandos planning on leaving the country. After a little haggle it was mine for $25 (RRP $70).
I know that many people on the Aussie Home Brewer forums manage to brew using a 25L esky-based mash tun, but the general concensus was that a little larger was better. My esky has quite a high lid and I wondered if Coleman included that in their volume specification. Of course they do! After measuring the internal volume with a tape measure I reckon I have 33L of useable space. That will go down slightly too, because my outlet won’t be able to go absolutely flush to the bottom. But still, I’m ahead of the 25L-brigade.
How does a mash tun work? The idea is that you steep your grain in water at a certain temperature for a certain period of time to extract the sugars and flavours. The temperature needs to stay as close to constant as possible – hence the insulated esky. Then the resulting sugar solution, wort, is drawn off through a manifold. The manifold is essentially a screen or strainer which ensures that the grain is left behind. The grain forms a cake or bed and further water can be ‘sparged’ through it to extract more sugars.
So the next step for me is to construct a manifold in the bottom of my esky. Naturally, everything that goes into the esky needs to be food safe at warm temperatures. PVC and some other plastics will leach plasticizers and other compounds which isn’t good for your health or your brew. I went with copper and brass – which are routinely used in hot water drinking supplies the world over.
The greatest challenge is working out how you’re going to put a hole in your esky without it leaking. Plenty of people on the AHB forums use a combination of threaded brass tube, flanged backnuts and homemade rubber washers – what I didn’t realise, until I visited the blokes at Gainforts plumbing wholesalers, is that we’re all making up a product that already exists – a tank adaptor. I looked it up on the Hansen website and it’s made from foodsafe nylon. And it only costs $8.
It comes with quite a large flange – which is excellent for spreading the load on the thin walls of an esky, but will need to be cut down on the bottom edge so that the manifold can sit nice and low to the bottom surface of the esky to minimise wort wastage.
Next up the copper manifold needs to be made. This is just a simple exercise in choosing a layout and cutting the pipe to fit. If you have a pipe-cutter this would take no time at all. I only had a hacksaw and it was slow but okay. The idea with the layout is to provide plenty of channels for the wort to drain out of the grain-bed into. The straight sections of copper pipe also need to be cut with thin slashes.
I sealed my tank adaptor up with some heat-rated foodgrade silicone sealant. SikaLastomer 511 is one such product. Don’t use normal silicone or even aquarium silicone – it isn’t designed for the purpose. Is $5 really worth being a cheap bastard over? (well, yes – but not in this context!)
The whole thing gets topped off with a ball valve on the end of the outlet. Mash tun ready!
Spend for my mash tun: $55.
Retail plastic mash tun $300.
Savings so far: $965.