stuccoing dome over insulation details?

[skinnydoc]

thanks Wiley... so perlite is the same a vermiculite?

thanks

ben

*** forget it I found the answer in the FB glossary, I guess they are the same thing. ben

[Mike D]

I would fill any gaps with vermiculite or perlite. It will help hold everything in place and give you more heat retention. I might even help your oven heat up faster.

Mike

[Wiley]

Ben,
Perlite is made of small pieces of volcanic glass which have trapped water. These small chips are very rapidly heated to a high temperature where upon they pop sort of like popcorn.

Vermiculite is a form of the mineral mica. It comes from alluvial deposits and is also mined. Lots of bad press several years back from the stuff mined in Libby, Montana which also had serious levels of asbestos with the finished product. Vermiculite available today is closely checked to be free of asbestos.

So they are not the same material. Be sure to wear a filter mask when working with either product and gloves are recommended when working with perlite. Eye protection advisable as well.

I would also recommend filling any free areas between the high tech insulation and the dome shell with either product as they are better insulators than a simple void. I did that with my WFO and even after several hours of firing the outer shell is still ambient temperature.

Insulation is good.

Hope this helps,
Wiley

[skinnydoc]

thanks guys...

so maybe just loose vermi- / perlite? I could rig up the mesh to be fine enough to retain it, or should I do the 6:1 vermicrete thing that FB talks about?

thanks for any details, very helpful in planning this out.

Ben

[Wiley]

Ben,
I went the route of fine mesh...in my case I used window screen. My thoughts went like this: My whole WFO is an experiment and should I want to change something in the future I can simply bore a hole in the stucco and with a shop vac and suck out the vermiculite. Thus I can reuse the vermiculite. Also I didn't want the excess water to have to get out of the structure had I gone with vermicrete. My rebar birdcage is attached via construction adhesive to the stand. Should I need to modify something I can run a sawzall around the bottom and the whole outer shell could be lifted off as one piece, again for reuse (theoretically at least).

So far I have not had problems that would necessitate such drastic measures. I used to work in boatyards and one rule of thumb regarding boats: Close something up so you cannot get access to it and you will need to get access to repair, adjust or replace. Same rule seems to apply to most things.

I'm also a big believer is redundant systems and having spare parts, but that is my own craziness and off topic.

Bests,
Wiley

[david s]

Ben,
If you decide to do a vermicrete or perlcrete layer don't go any richer than 10:1 Even then you are adding as much mass in cement as vermiculite and that only reduces the layers insulating capacity. You only need it just strong enough to hold in place so you can stucco over it.also make sure you give the layer plenty of time to dry because it takes up double the quantity of water that standard concrete takes and that water needs to be removed.

[Mike D]

Just fill it in loose. That's what I say. There is no need to make it heavier than it needs to be.

Mike