The mash tun is where the starches in the grain are converted to sugar to be fermented later by the yeast. In this system the mash tun takes the form of a 100 litre stainless steel vessel. I have made a slotted manifold from 22mm copper through which the wort exits the mash tun for recirculation or running into the copper. On the underside of the manifold are slots cut every 10mm with a hacksaw.
Here’s a couple of photos of me doughing in which is the process of mixing the grains with water heated to strike temperature. Strike temperature is dependant on the temperature of the grain and the thermal mass of the mash tun. Typically to get a mash temperature of 66-67°C I need the strike temperature to be 75°C. This temperature will vary from system to system depending on how well insulated the mash tun is and whether you preheat it.
It’s worth noting that the mash temperature remains very stable in my system even without the recirculation purely due to the thermal mass of such a large amount of grain. I can mash 15 kg + of grain and it will remain at 66-67°C for well over an hour even without insulation.
Once I’ve doughed in I let the whole mash sit for a few minutes before I commence recirculation. This pause allows the grain to take up the liquor and settle down into a stable mash bed so that, when I start the pump I don’t suck grain into the recirculation system.
Recirculation is carried out by pumping the wort from the mash tun, through the PID controlled heat exchanger and back through the return manifold.
Here’s a photo of the return manifold in action. This photo was taken after just a few minutes and already you can see the clarity of the wort.
After an hour or more of mashing all the starch is turned to sugar so it’s time to start the sparge.
Sparging is the process whereby the sugars are gently washed from the grainbed in the mash tun. There’s a couple of ways you can do this; batch sparging or fly sparging.
I used to fly sparge which means that I sprinkled hot water on top of the grain bed whilst pumping the wort to the copper from the bottom of the mash tun. Batch sparging is achieved by effectively mashing twice and running off the wort completely each time. There are benefits to each method of sparging; batch sparging lessens the probability of extracting tannins due to the fact that the pH remains lower than when fly sparging but fly sparging is more likely to give you a better quality of wort due to the ability to cease sparging earlier. I’m sure the batch spargers out there will dispute that statement but this is my page so I’ll write it how I find it!