I've read that site before, and it does have some good information. My take is that it doesn't say that you can't do a step mash. It says that a HERMS isn't ideal for it, and that's his opinion. His reasons are valid. However, I still think a HERMS is better than the alternatives, and it certainly is better than my previous alternative. I used to pull out some of the wort, heat it on my stove in a sauce pan, and pour it back on top. This was a major pain. The next obvious alternative that comes to my mind is a direct fired mash. That certainly risks temperature gradients and denaturing enzymes too.
I don't get 4 degrees/minute temp rises. It is probably more like 1 degree/minute over the course of the step. But it is not at all linear in my system. That's why I want to install a PID.
When I do a step mash I don't start with my HLT water at 170. As described above, it starts around 150 or so, probably a little more. I never thought about exactly +3 degrees, but that's kind of what I've approximated, maybe 5. I think the difference makes the step go faster. However, if you had no difference at all, you could still get your mash to the desired temperature, assuming a lossless system.
Consider this. Mash is at 122. HLT is at 150. Wort is pumped out of the mash at 122, heated to 150, and then back into the mash. At the beginning you have 150 degree wort at the top of the mash tun, and 122 at the bottom. Now what happens when you keep recirculating? Well, you draw out more 122 wort and replace with more 150. The 150 wort is permeating more and more into the mash bed. If you recirculate all of the wort, the entire mash will be 150. Now the grain is holding some temperature, but not as much as the liquid. So recirculate more than the entire mash, or have the HLT temp a little higher to compensate.
Brant wrote:
The guy said that if you have your water temp at your target temp the only part of the mash that will be at your target temp will be the very top of your grain bed and the rest will only slowly heat up.
I reread what that guy said, and really he isn't in conflict with what I wrote above. His point is that you have to recirculate the entire mash, and that takes time. I don't disagree with that.
I do run my pump pretty slow. I got a stuck mash once from running too fast and don't want to repeat that. Also, if you run the pump too fast you really aren't getting full use of the heat exchanger.
Now that I think about this, the temperature gradient goes a long way in explaining the non-linearity I've observed. The temp rise is very slow at the beginning, at which point there is hot stuff on the top and only some minimal conductive heat transfer to the bottom. My thermometer is reading the temp near the bottom.
-Eric
