Vermiculite

[dbhansen]

My local big-box retailer has 4-cubic-foot bags of vermiculite ($9 ea.) sold as "MicaFlake attic insulation." It's 100% vermiculite. I haven't opened the bag yet, but it looks like fine flakes, 1-2 mm across. Does this sound okay as loose oven insulation?

[toddj]

regular vermiculite is mica popped like popcorn - i think

depends if it is flat flakes or fluffy

[Breven]

I don't think that's right. The price alone makes me think it's not the right stuff. I think typically you'll spend $20-$30 on a bag. Also, if it's designed for attic insulation, I'm guessing that it's not designed for high heat.
However, since this is extra insulation, after the blanket- I doubt it will hurt anything.

[egalecki]

Not sure about the contents of what you're looking at, but as far as price goes, around here you can get a 4 cf bag of vermiculite for anywhere from 13 to 20 dollars a bag.

My verm. is brownish, and the particles are about the size of scoopable (the clumping kind) kitty litter. Or maybe kosher salt.

If it says it's 100% vermiculite, I don't see a problem. My verm. came from a pool supply place, so what it's originally intended for isn't really important sometimes.

Unless they're building pools in hades now...

[Breven]

You may be right Elizabeth.
I checked out the manufacturer of the stuff I used and they do have differnent grades and uses, some with additives, some withou. But it's all basically the same.

In this application, I would guess that the course stuff would be best. Aside form the insulating properties of the vermiculite itself, the air pockets inbetween each of the little pieces of vermiculite help insulate. But it should all work.

[dbhansen]

Thanks for the info! I'll have to open a bag and take a closer look. The only local pool supplier with vermiculite says it comes pre-mixed with cement, so that's out.

The bag I have does say it has been expanded with heat already, but it might be a finer grade than some.

[egalecki]

My supplier offered me the vermiculite with portland added- I was strongly tempted, but I didn't know what the ratio was, so I said no. It might be a good way to avoid having to mix it, though... I just didn't have the intestinal fortitude to attempt to figure the ratio on my own... math is NOT my thing.

[Johnny the oven man]

Vermiculite is normally "exfoliated" at over 1000c. The mix ratio is usually by volume. The normal ratio is say 6:1, that is 6 scoops of V'lite to 1 scoop of cement. We usually use Cement Fondue as the binder. Exfoliated V'lite looks like little accordians.Size 3 is about right. 100litre bags are $30 here in Aus.