Have any of you who mash in coolers fabricated a mash cap for low oxygen brewing?
I was thinking about getting something like the below and trimming it down to size (need to measure my tun to figure out what size I need).
I don’t know how well it will float. While it would be less dense than water, I think a slight break in the surface would cause it to go down. This is because of the flexibility. A more rigid solution might work better.
ETA - it’s cheap enough to give it a shot.
I used several layers of foil, sort of rolled and crimped on the ends. The foil was slightly bigger than the inside of the cooler, so that I could mold it to the edges and corners. Not sure if it’s a long term solution but it turned out a really tasty beer.
I imagine your rolled edges create rigidity. Aluminum isn’t an issue?
I asked Bryan this and he didn’t seem to think aluminum was a problem…
The egdes were loosely enough rolled together to still let me mold it for the contours of the cooler. You mean a safety issue? I’ve read of guys using foil for a mash cap. It was cheap and around. Iknow there are different grades of aluminum but lots of brewers still use cheap aluminum kettles.
I wasn’t thinking safety as much as causing some anti low o2 voodoo
I just made a mash cap out of 1/2" thick closed cell foam yoga mat or camping ground pad material. It works well. Its easy to cut to shape. I did add some 1/4" wood strips to the top of the cap to serve as stiffeners. I used Goop to glue the strips onto the foam. Goop is full of nasty smelling volatiles, so it took several days of airing out for the smell to go away. But the good thing about Goop is it has a tenacious grip. Silicone glue would be less toxic initially, but it doesn’t stick well enough.
I do have a piece of aluminum flashing bolted with SST bolts on the underside of the cap to deflect the return flow along the underside of the cap. Aluminum is not a problem for use in wort since it is essentially insoluble when the pH is between 4.5 and 8.5. It will corrode when the pH is outside that range. We are safe to use aluminum in the mash tun and kettle.
I tried making a mash cap out of corroplast material, but that warps badly when heated and I could get the hollow cells sealed well enough.
I like that idea for a more permanent solution. Thanks, Martin!
Yea, Aluminum foil can work and its cheap, and easy enough to mold to whatever. Uee it to cap your preboil, and all the vessels on transfers, since it will adhere pretty tight and float as the volumes increase/decrease.
Yoga mats? Like Subway? There’s gotta be a better way, IMO
There is. We speak about it here: http://www.lowoxygenbrewing.com/uncategorized/limiting-oxygen-exposure-on-the-hot-side-via-caps/
Though it’s not a 1 size fits all solution, nor “cheap”.
What about when you use a RIMS system? Also, does it make that much of a difference at the micro level of 5 gallon batches?
Doesn’t matter what type of mashing system is used. The smaller the batch the more important it is.
I have this one: http://vlaamshobbybrouwforum.be/forum/index.php?topic=4753.msg86029#msg86029
Silicone mat not for baking, but for rolling out dough. You have to be sure that it floats 
Thanks for the pics. Here I was thinking that I needed something to rig up something absolutely snug-fitting to make this worthwhile at all. It looks like I just need to find a cake pan that fits pretty close to the walls of my cooler, possibly padded with some aluminum foil to make the gap as small as I can - the goal being to mitigate air exposure rather than eliminate it entirely, right?
Mitigate if you are using SMB along with it. If not using SMB elimination is needed( sealed containers, inert gases, etc)
Lets see…using an inert plastic to cap my mash??? Yeah, that’s fine. I’m not eating it.
You aren’t stupid enough to believe ANYTHING that Food Babe says…are you?
Sarcasm doesn’t come across very well via text, does it?