So you have made the jump to all grain brewing. Your mash tun has the kinks worked out of it, your sparge methods are pretty sound, and your efficiency is consistant. There is no need to change a thing with your process right?

Well that is a matter of opinion. For most everyone in the AG world, we do not have direct fired msahtuns. This makes temperature control possible by only two means. One is infusion of more water to the mash at a higher or lower temperature to adjust the overall mash temp, or transferring the heat from another source to the mash.

Why is this even necessary? Well many recipes call for a certain mash temperature to be held. A lot of mash tuns can lose heat over the course of the mash, mashtun efficiency can vary but a swing of 3 to 5 degrees during the duration is not uncommon. The lower end of the temperature window will produce a higher fermentable wort with a thinner body, more alcohol and less mouthfeel. The higher end of the window will produce a less fermentable wort, with a thicker body and provide more mouthfeel. Knowing this, many of us want to have a target mash temp and stick to it.

There are also advantages to a stepped mash. The starch to sugar conversion happens within two seperate ranges. Without getting into chemistry and keeping this simple the optimal ranges are 142-145 degrees, and 153-156 degrees. Most who do a single infusion mash will pick a temperature of say 150 degrees and try to get the best of both worlds, but are not hitting optimum circumstance. To do this a mash rest at 144 deg for an hour and 155 deg for 1/2 hour would be better. Some pilsner malts also benefit from a protein rest at 122 deg as well. Almost all other malts are “well modified” and the maltsters say a protein rest is not necessary.

So how do you get complete control over your mash without a direct fire tun? You could start with a thick mash at your first target temp, then add another infusion of near boiling (200 deg) hot liquor. How much to add can be tricky, I’ve played with this a bit and need far more than recommended to move the temp, failed attempts and definately not pinpoint accurate. That leaves us with the other option which is heat exchange.

There are two methods that are widely used in the homebrew world, A Heat Exchanged Reciculated Mash System (HERMS) or a Recirculating Infusion Mash System (RIMS). The latter of the two incorporates a heat source (usually electric) element that is included in the plumbing of a recirculating system. The wort is drained slowly out of the tun and passed through plumbing which heats the wort to a higher temperature then pumps it back into the tun. A HERMS does pretty much the same thing except the wort stays contained amd the heat is transferred to the lines by an out of plumbing source, usually hot water.

This is my simple design. A 25 foot immersion chiller works great. If you do not have an immersion chiller you can take a lesson out of a previous blog well written on how to make one. If you use your immersion chiller to do your actual chill then quick disconnects might be a good idea. You want to set the circuit up to go from your mashtun drain valve, to your pump inlet, pump outlet to your IC inlet, Your IC outlet to your mash tun inlet. The IC you want to place into a boil pot, (I use my keggle). The wort will then be pumped out of your mashtun, into the IC, (which is now doing the opposite of its intended use- it is heating the wort not cooling) then re-introduced back into the mash thus raising the overall temp.

A typical mash cycle may include striking the grains with 159 degree hot liquor getting an initial mash temp of 144 deg. After 1/2 hour a drop of 1-2 degrees may occur, that is when you would recirculate and have the water surrounding the IC (your new heat exchanger) at 170 deg. When this loop runs for a few minutes the mash will go back up to 144 or 145, shut down or restart the loop to maintain within a couple degrees your target. After an hour, have the exchange water heated to 180 deg, and turn the loop on again, depending on the coil diameter, coil length and mash volume, you should be able to raise the temp from 144 to 155 in about 8-12 minutes. Then after it rests at 155 for 20-30 minutes, crank the heat exchange water up to 200 deg. Run the loop again and a mashout temp of 168 deg should be reachable in another 8-12 minutes. After playing with the system some you can figure out how long it takes to raise the exchange water temp up so it is ready when your mash is.

Besides absolute control over your mash temp to within 1-2 degrees of accuracy, there are a couple of other benefits. Because of the constant recirculation, a nice clear wort will be produced making vorlauf unnecessary. When it is time to drain and sparge, open your drain tube and fill your kettle with clear wort void of husks. The second is improved efficiency. With a proper conversion temp, a proper mashout temp, and constant grain rinsing, just about every bit of soluble sugar is collected. A higher efficiency means less necessary grain making life easier and brewday a little cheaper.

A couple of quick tips. First, there should be some type of sparge manifold or diverter above your mash during the re-introduction of the wort. If not, like fly-sparging the new wort can cause channelling and not be raising all of the grains’ temp. The other is to clean out the IC, by disconnecting the line from the mashtun and reconnecting it to a hotwater source, then pump the hot water through to clean out any wort back into the tun, when it runs clear, you’re clean!

This may not be a must have for everyone, but I figure if you are doing 10 gallon batches or larger, a pump is probably already in place, why not add some more control to your fingertips.

Prost!