I’m looking at designing a mash-tun. One of the homebrewers I know made one with a Colemans picnic cooler (47L, I think), stainless steel braided plumbing supply (with the hose inside removed), and a brass ball valve. It looks like this:

Inside the mash tun

Inside the mash tun

The tap

The tap

When I first saw this, I was quite surprised. I’ve read on How To Brew that mash tuns should have multiple channels, not just one.

My friend explained:

My first few brews with it were batch sparges.

For fly sparging, with the stainless steel braided plumbing supply hose there is increased chance of channeling (the sparge water wearing grooves in the grain bed) and therefore severely decreased efficiency.

I really wanted to try fly sparging though, because I have the sparge arm from B3. So I set up a gravity fed system last weekend. I went really, really slow. I used a large sheet of aluminum foil on top of the grain bed and maintained a two inch (5cm) head of water over the grain. My efficiency was 80%.

My batch sparges are [also] consistently 80% because I drain extremely slowly. I allow 15 minutes after mashout before I collect first runnings. I go a bit longer during the batch sparge and usually collect less than a liter per minute.

I have to confess I didn’t really understand what a batch sparge or fly sparge was, so I googled it and found this explanation:

With fly-sparging, also known as continuous sparging, the goal is to match the input of sparge water from the hot liquor tank to the runoff flowing into the kettle in order to maintain a constant volume of water in the mash tun. As clear hot liquor slowly flows into the mash tun it dissolves more extract which is then flushed into the kettle.

With batch-sparging, you first completely drain the mash tun into the kettle. This is similar to methods employed by most homebrewers when making high gravity worts. However, once the first runnings are collected, an additional amount of hot liquor is infused into the mash tun, stirred to help dissolve more extract and then drained again into the kettle.

Now I can see that what I did with Hitachino was fly sparging. What I do at home with the grain bag is more or less batch sparging.

With fly sparging, if there are channels then the water has an “easy path” out and wont extract sugars as it passes through. With batch sparging, since you’re draining the entire wort, channelling is not a problem – hence the design above being acceptable.

Eventually I want to do HERMS – and for that I’ll need a copper manifold which has less risk of channelling. But as a simple way to get started, without having to faf about with copper, I might try the approach above – when it comes time to do HERMS, all I need to do is take out the steel braided line and replace it with copper.

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