Rebuilt - In a previous thread discussing mash tun draining issues, you made reference to a “skin” that can build on top of the grain bed, impeding flow. You also mentioned “raking” the top to break that skin.
I’ve never heard of this, but think it makes some sense and may be affecting my flow when mashing with the usual suspects (wheat, corn, etc.) The recirc seems slower and my efficiency drops a bit when using those in the grist.
Would you mind explaining a bit more about the skin and how aggressively you can rake it? I don’t want to disturb grain bed too much, but want to make sure recirculation isn’t slowed down by skin.
I’m planning on brewing my pumpkin ale this weekend, in which I mash a lot of canned pumpkin.
I’ve always found your posts insightful, and would appreciate any additional commentary! Cheers!
Proteins in the mash can form a skin on the top of the mash inhibiting mash draining.
Cutting the mash using a plastic mash paddle or even a butter knife, depending on how deep your grain bed is in relation to the liquid in the mash tun, can allow the liquid to drain through the mash.
While not a substitute for proper crush, rice hulls and a good mash tun design, it can facilitate the draining of the mash tun.
A collapsed grain bed or one that is sucked tight should be corrected at the source of the problem first.
When cutting the grain bed, continuously make a crisscross pattern, like cutting a pan of brownies, about 1/2" - 1" deep.
If your mash tun still doesn’t drain, drains very slowly, or you have to cut the mash very deep, you have other issues that need to be resolved first.
jd14t beat me to it, and describes the process very well.
It used to be one of those standard recommendations you’d read in brewing books about how to get better lautering while fly sparging. Sometimes you can get some good tips by looking at the ways people got around various problems. I’ll still rake the top of the bed once in a great while; usually for reasons like you brought up: high protein adjuncts present in the mash.
I do 10 gallon batches and mash in a keggle, so it’s a pretty “tall” (for lack of better terms) grain bed.
I use HERMS to maintain mash temp. The flow of the recirculation is fast at the beginning, but can slow down substantially after 30 minutes into mash (especially with wheat, corn, etc.) Seems like the speed of the flow is compacting the grain bed very tight, but I need the high flow speed to maintain the mash temp via HERMS.
I’m confident in my crush (>.03) and already use rice hulls. Since I don’t want to buy a wider mash tun and redesign, I think I’ll give the raking a shot.
