vermiculite

[ddonald]

I found a very reasonably priced source for vermiculite. It is some distance away. The company says they use it for packing material and it reads No. 4 on the package. I can't find anything on the internet indicating just how large size No. 4 is.
Does anyone know the answer to this and is it suitable for the portland/insulation layer.

thanks,
Dave

[GianniFocaccia]

This chart doesn't indicate grade either, but my guess is the Premium grade (presumably #1) would be the most expensive. The vermiculite I bought didn't have particularly large particles, nor were they super fine. Somewhere in the middle I'd guess. Have you checked HD?

Vermiculite Grades

[ddonald]

HD has 2 cubic foot bags for $19.97. I can get 4 cu. ft. of No. 4 for $13.

Dave

[leckig]

4 cu ft for $13 is what I paid. Get about 10 bags if you insulate both the dome and the hearth with it. Maybe the guy can open a bag and describe the size to you, the bigger the better. I had one bag of a very fine vermiculite and it was very easy to work with but I dont think it insulates that well

[md.guthrie]

Normally Perlite is cheaper than vermiculite. I just purchased 45 2 cu.ft bags for approx. 17 $ per bag

[fxpose]

Originally Posted by md.guthrie

I just purchased 45 2 cu.ft bags for approx. 17 $ per bag

Let me get this straight. You paid $765 for vermiculite?
If they were used solely for insulation purposes you would have saved money using ceramic boards and blankets instead.

[md.guthrie]

Did both. I want to retain maximum heat...... Trying to get it right the first time...

[leckig]

man... nearly $800 on vermiculite. This is about half what I spent on the whole 42 inch oven.

[ddonald]

My No. 4 vermiculite finally came in yesterday. It was $13/4cu. ft. bag. The pieces vary greatly in size with the largest about 3/4 x 1/2 in down to quite small pieces.
Now the question is: at what ratio do I mix it. I see blogs using 1:6 up to 1:10.
Is there an ideal ratio? Any tips on mixing and finishing would be greatly appreciated.

Dave

[leckig]

for under the hearth insulation you do 1:5 - because of the weight that will sit on it. I very much recommend you buy the insulation board as well, I wish I did.

For dome insulation: the less cement the better, but less cement you put in the mix the harder it is to apply. Most people do 1:10. The way I did mine was also 1:10, one day I piled up about 6 inch layer on the dome about 12 inches high, I let it set for a day and I continued the next day all the way to the top.

When I tried to do it all in one day it was always falling down.