Two Mash Out Options


At the beginning of wort collection, it doesn’t matter if your grain bed temperature climbs above 170 °F (77 °C); tannin extraction is largely suppressed at mash pH.

At the end of your mash, you have the option of mashing out — raising the temperature of the mash to 168–170 °F (76–77 °C) — before recirculating and collecting your wort. The best reason to mash out is to make lautering easier. The hotter the mash, the lower the viscosity of the entrained wort and the easier it is to drain it away from the grain solids in your lauter tun. However, the difference in wort viscosity between wort at typical mash temperatures (148–162 °F/64–72 °C) and wort at 168–170 °F (76–77 °C) is not that great, and so many homebrewers simply skip this step without any noticeable negative effects. (For brewers who mash in a converted picnic cooler, often the volume of boiling water necessary to raise the temperature would cause their mash/lauter tun to overflow.)

I can heat my mash tun, so I usually mash out with the idea that at least it can’t hurt. (Plus, it requires me to stir the mash and that might help out my extract efficiency a little bit.) I like to tinker with my brewday procedures, and in this article I’d like to present two alternative ways to mash out besides the usual heat-and-stir and add-boiling-water methods. I’ve used the first option a number of times and it works fine. I accidentally did the second option a grand total of once — and it wasn’t until after the fact that I realized it might be a good idea. So, treat the second option as something to consider, not something that has been thoroughly tested.

Extra Hot Sparge Water

The first option involves slowly mashing out over the course of wort collection. Instead of heating the mash to 168–170 °F (76–77 °C) and then sparging with water hot enough to keep it around that temperature, I skip the initial mash out, but sparge with water at 190–195 °F (88–91 °C). When I do this, grain bed eventually creeps up to 170 °F (77 °C) near the end of wort collection. Then I just add unheated tap water to my hot liquor tank (HLT) to cool it down to the correct temperature needed to keep the grain bed at 170 °F (77 °C) and finish sparging.

This works fine, but the more I thought about it, the more I realized that this really wasn’t doing much for me. The time that lower viscosity is going to help the most is when the wort is at it’s most dense. By the time my grain bed reached 170 °F (77 °C), the wort density was down under SG 1.020 and really wasn’t that much different than water. (The extra heat did, I suppose, mean that it took me slightly less time to reach a boil, but who cares?) Then, after a brewday in which I overshot my mash out temperature, I thought of a better alternative.


Hot Mash, Cooling Sparge Water

My second idea is to mash out to a temperature above 170 °F (77 °C), then sparge with water cool enough to bring the temperature down to 170 °F (77 °C) before the end of wort collection. The mash would then be hottest at the time when the wort is at its most dense, and when a difference in viscosity is going to make the biggest difference.

Of course, one thing many brewers will wonder about is tannin extraction. In the old days, we were all told that if your sparge water was over 170 °F (77 °C), you would extract excess tannins  from the grains and your beer would end up astringent. Of course, we now know that — given the rate that homebrew setups lose heat — your sparge water needs to be heated above 170 °F (77 °C) to maintain the grain bed temperature at 170 °F (77 °C). In addition, if tannins are going to be extracted, that will happen near the end of wort collection, when the pH of the grain bed has risen to 5.8 or above. Around mash pH, tannin extraction is not favored, even at temperatures above 170 °F (77 °C). When brewers do decoction mashing, they actually boil about a third of their mash. Decoction mashing does lead to more tannin extraction compared to infusion mashing, but usually not so much as to make the beer unpleasantly astringent.

Here’s how I see this idea working. After mashing, I would heat the entire mash to about 185 °F (85 °C), 15 °F (~8 °C) above 170 °F (77 °C). I would then heat my sparge water to 155 °F (68 °C), 15 °F (~8 °C) below 170 °F (77 °C). I would start adding sparge water once the level of liquid was at the top of the grain bed and collect the wort, measuring the temperature of the top of the grain bed every 5 minutes or so, just to ensure it dropped to 170 °F (77 °C) or below by the end of wort collection. (And if the temperature dropped below 170 °F (77 °C) by several degrees, I probably wouldn’t worry as the wort is thin near the end of wort collection anyway.)

If this works — and it seemed to that day I got distracted and overheated my mash — it could make it easier to lauter brews with large amounts of rye and perhaps also increase extract efficiency a bit. It really doesn’t involve much of a change from my normal procedure — I would just heat the mash a little more during the mash out and the sparge water a little less.

In order to do this, you’d either need a mash tun that you could heat, or you would have to mash in your kettle and then scoop the grains over to your lauter tun. In that case, you’d need to heat the mash a couple extra degrees to compensate for the loss of heat when transferring the mash between vessels. I’ll give this a try a couple times this year and report back when I do.



  1. Hmmm. Interesting. I’ll give it a try.

  2. Hey – John Palmer says that heating the mash above 170 is a bad idea because bitter tannins will be dissolved out of the malt hulls. So, I’m not sure this is a good idea. How did it work for you?

    • That only applies when the pH is over 5.8 (and I mention this in the article). In decoction mashes, roughly a third of the mash is boiled (around 215 °F). It works fine.

      • On a homebrew level, this will be even more confusing. I think advising it will be unfortunate outcomes for many novice brewers.

  3. So, can you tell me how it worked out for you? Seems like a good idea at face value!

  4. David P Medici says

    I wanted to put in my two cents.

    I have been brewing since 2003 and all grain brewing for 7 years now. My take away from the Sparging process or decoction process is that 1. Reduce any tannins (NO matter what your pH is. Tannins come out in acidified liquids, and when any liquid is heated in this case either the Mash or the resulting wort, the pH at STP (standard temp and pressure) is NOT what you have under heated conditions. In fact the pH drops when heated, thereby making resultant liquid from the lautering even lower. A darker brew means more tannins and more over tanninization if you are not careful.

    With all that being said, the science of beer making is fun. Try it, if it works you discovered an undiscovered country. If it fails you have figured out something.

    Ashland, VA

  5. This is not sound. Mashing at any stage above 170 is highly undesirable.

    • Why? Based on what you’ve read or your own experience?

      I had a failure on my temp controller during one brew (scotch ale) and didn’t notice until my mash had spent 20 minutes climbing up to nearly 190 towards the end of the mash, but I finished the process and brewed it out anyway. I couldn’t detect any astringency in the final beer, in fact it turned out great.

      Here’s my 10c on brewing: There are no rules, only guidelines, just figure out what works for you…

      The brewing world is full of “you shouldn’t do that, it will ruin your beer” advice based on what someone has read, but I’ve made some big mistakes and tried some pretty unusual ideas just to see what would happen, it’s taught me not to pay much attention to what people say, if they aren’t basing it on personal experience.

      Also there’s a reason why John Palmer keeps releasing new editions of How to Brew, because he’s still learning and correcting himself as well.

Speak Your Mind