Insulating blanket question

[pjk]

Hi,

I have a question about applying ceramic fibre insulating blanket. Once I place a layer or two of the blanket (25mm, 1" per layer) over my bricks and cover it with chicken wire, how should I apply the next layer of vermiculite/fondue render.

Should I place it on heavy and compress the insulating blanket down as much as possible, or do it lightly and leave the air layer in the blanket as much as possible, or should it be applied somewhere in the middle?

Cheers,
Peter.

[dmun]

The blanket is fairly dense and the vermiculite concrete pretty light. You'd have a hard time compressing it with this stuff even if you wanted to, which you don't.

The problem people have is with getting it to stick. You may want to do it in two stages, building a ring around the bottom, then using that to support the layer on top the next day.

[pjk]

That sorts that question out pretty quick, I hope the trend continues.

cheers,
pk

[CanuckJim]

PJK,

I've done a fair bit of work in this area and found a few tricks that might help. One: make sure the chicken wire is tight to the blanket. You can do this by cutting it and stitching it up with the cut ends so there are no bulges.
Two: get a spray bottle and mist the blanket before applying the mixture. This might lengthen your cure time somewhat, but it really helps with sticking. Three: most vermic or similar mixtures do no like staying on near vertical surfaces, so begin with a fairly thick layer and go from the bottom up. Hold the stuff in position for a count of ten before removing your trowel.

Jim

[nissanneill]

Hi Peter,
check out my experiences with exactly your predicament at:

http://www.fornobravo.com/forum/f21/...-4-a-2045.html (Neill’s Pompeii #4)

I found that you start with a 5:1 mix vermiculite: portland at the very top of the dome and work your way down and around. I also found that the first coat was the hardest and added approx 1/2 pt of fireclay which made it stickier.
I used a brickies trowel (as I didn't have much room to work with a hawk) to hold the mix and a steel cement trowel to scape it off and ALWAYS work your material UP! It will simply continue to fall off if you don't but you soon work that out. Don't try to put more than a 1" layer on at a time, again I found that it causes more trouble than it was worth. Apply 3 X 1" layers and that should be enough. My oven at 500°C inside is cold on the top outer dome.

Neill

[fsucpa]

Is it that much more to skip the vermiculite and just use another layer or two of the ceramic insulating blanket. Seems the the blanket only might be better anyway. What do you guys think?

[asudavew]

Originally Posted by fsucpa

Is it that much more to skip the vermiculite and just use another layer or two of the ceramic insulating blanket. Seems the the blanket only might be better anyway. What do you guys think?

Here's a link to James' discussion on that subject.

http://www.fornobravo.com/forum/f6/i...iency-218.html (Insulation Efficiency)

It has very useful info that should help you.

[nissanneill]

It all dpends on how you wish to finish your oven and where it is.
If it is outside and you wish to maintain the igloo shape, then I would certaoinly vermiculite cement coat the dome. If however, you have an inside installation OR intend building a waterproof housing, then the extra cost for the extra layers of superwool would do the trick.

Neill

[fsucpa]

actually, I would have thought quite the opposite, in that a box-like housing could easier contain the what appears to be a pain in the butt loose vermiculite, as opposed to the igloo, where to pour some kind of vermiculite layer over the ceramic blanket insulation, and then hope to seal it with that final mud layer would seem to be much harder. By the way, that mud layer that goes on after the ceramic blanket/vermiculite, why are we using that final mud layer. Seems like a couple of extra layers of blanket, then chicken wire, inside a box like structure, bam, your done? Obviously, you can tell I am a newbie?

Tom

p.s.- also, can someone comment on the relative costs of using said extra layers of insulfrax vs insulfrax and vermiculite. In addition, could someone also comment on the use of insulfrax vs kaowool, which is also a ceramic blanket,vs " Safe" non-cermic blanket, described as "This is the "Body Fluid soluable" non-ceramic fiber blanket" "This Roll is the Superwool 607 Max product rated at 2192 F degrees continuous use". this stuff seems to be half the cost of the kaowool.

So, again, that is kaowool vs insulfrax vs non-ceramic blanket vs insulfrax/vermiculite.

Thanks for help with this seemingly complicated subject.

[pjk]

Guys,

Thanks for the tips and the links, great info.

Cheers,
Peter