Crumbly Vermiculite/Portland Cement

[benguilford]

O how I wish I didn not have to work full time, that I could experiment all day long, I could make samples and run tests on them... sighs...

[eatingmorefood]

Getting ready to add a layer of 50% vermiculite and 50% perlite with cement mixture. Not sure how much cement to the vermiculite and perlite. Planning on a few inches on top of my roof. and a few inches on the sides of my Bella square oven. Entrance and insides are almost done, build pics are located here: http://www.chefdepot.net/woodoven.htm

[Lill Dave]

I used a 5 to 1 perlite mix that works real good .
Thickness is 3.5 in with a 1 in layer of morter over that.
The outside of my pompaie oven reaches 150 degres so I would advise at least 5 in. of insulation on the outside of the oven.

[eatingmorefood]

Lil Dave,
thanks for the recipe. You used a 5 to 1 perlite mix that works real good .
Is that 5 parts perlite to 1 part mortar mixed ? Ratio of 5 to 1 by volume?
thanks!
Eatingmorefood

[Lill Dave]

Not morter cement,mix 5 to 1 dry then add water. It's real important to mix it dry.Yes by volume.
You can also use vermuclite same ratio , same mixing, I'm telling you this because one of these products costs half as much as the other .
I think vermiculite is the less expensive.
Good luck

[Neil2]

I suggest a 5:1 or so only for the weight bearing layer under the hearth.

For insulation layer, such as over the dome, use a 12:1 mix or so. This will have a much higher insulating value but still be more than firm enough to support any surface finish such as rendering or stucco.

[eatingmorefood]

over the dome, use a 12:1 mix or so. ..


So then after mixing these 12 parts vermiculite to 1 part cement in wheelbarrel, then add enough water until it is like paper-mache ? Is this correct ? thank you much !

[Neil2]

"then add enough water until it is like paper-mache ?"

Yes. Mix gently with hand tools. Just enough water so it is "workable" and sort of sticks together is best. The actual water content is not that critical.

[benguilford]

I find it easiest to mix by hand sometimes, just get some long rubber gloves and get up to your elbows in it! Good times

[eatingmorefood]

Thank you for the recipe. I will be working it soon.