German Brewing

Silicone rubber cap - that's a great idea. I use a silicone drop tube also. I was thinking of relocating it below the liquid surface, so I could cap properly. Wouldn't be necessary with oil but probably would help with a silicone cap.
Thanks for this great idea.
-Ski

But it would be good to check that it floats! Silicone has a density of 1.1-2.3 kg/L, heavier than water, so it will probably sink. Silicone sponge may work. This stuff is FDA approved and has a density of 420g/L, so it should float:
http://silicone.co.uk/products/silicone ... ne-sponge/
Ski

Does the increased surface area of a sponge compounded with the air-holding ability defeat the purpose?

Sponge has 3% absorption. Probably not the best material. Also, we may need to consider O2 permeability.
I was looking at polypropylene or one of the other plastics as a possible alternative. Comes in sheets, and density is about 0.95 kg/L, so it should float. Used in lots of low-cost electric brewing kettles, good for 130C. Oxygen permeability is not ideal, though. http://www.faybutler.com/pdf_files/HowH ... ctGas3.pdf
It may seem like permeability wouldn't matter much, since there time is short (60-90 mins) and the no pressure differential, but I think that if the liquid has no O2, then there will be a strong effective pressure pushing atmospheric O2 into the solution.
PET has lower permeability, but is too dense (about 1.3kg/L). Oddly, Saran wrap has very low permeation. Metals would definitely be the best for low permeability: stainless steel or aluminium foil. I don't know if Aluminium Oxide would get stripped off Al foil in a mash. Perhaps Al foil on top of a floating plastic disk would work. This is why I was considering vaseline oil - floats, adapts to any shape, cheap, and is already relied on to keep O2 out of liquids. Only downside is it's a consumable.

Re: the oil. I would think the only issue would be if it mixes. I do a lot of recirculation, both to maintain mash temp as well as to raise temp between rests. If you do a very calm single infusion and rack from under the oil you should be fine. I don't know that it would contribute flavor issues (depends what it tastes like), but could affect head retention down the road, perhaps? With winemaking, it's a much calmer process, especially for aging.

I dunno, I found it much easier to just take a lid that fit my pot, cut off the rim and get a silicone gasket for it and call it a day.



Cut and in place.



Return manifold on the bottom

With the gasket it is pretty much 100% sealed, and uses pressure to stay in place. I just set it until I get a little liquid push up and over.

Sorry, yes I do.