Exterior Dome Finish

[builder brad]

Quick question.

I am going to be using a ceramic blanket on my dome - should have 2 inches or more, depending on coverage. I will then place some 1 inch galvanised chicken wire over this and cap this off with a cement/ perlite or vermiculite mix to about 2-3 inches.

my question is which is better verm or perlite for the top layer, and is it then weather-proof, or will I need to do a final concrete/ stucco layer over this?


thanx in advance

[asudavew]

Originally Posted by builder brad

Quick question.

I am going to be using a ceramic blanket on my dome - should have 2 inches or more, depending on coverage. I will then place some 1 inch galvanised chicken wire over this and cap this off with a cement/ perlite or vermiculite mix to about 2-3 inches.

my question is which is better verm or perlite for the top layer, and is it then weather-proof, or will I need to do a final concrete/ stucco layer over this?


thanx in advance

\
Either is fine. I prefer verm because I think it is easier to work with.
As for waterproof- Nope
You will have to stucco it. Or cover it with a structure.

I would also go with a little more than 2-3 inches of vermcrete.
I have about 1 inch of blanket and 6-8 inches of perlite and verm all over my dome, but it's loose, no cement. Then that is covered with an inch of mortar and finally stucco.

Even with that much insulation . I can still find warm spots at times.

But the oven will usually stay hot enough to cook up to 48 hours + after one pizza firing.



Dave

[builder brad]

Cheers Dave!

[builder brad]

I just looked at your thread, nice work!

reading your previous posts - I thought that you said perlite was easier to work with for the outer coating, not vermiculite? - I really want to learn from other peoples experiance and save myself time and effort.

regarding the overall insulation layer for my oven I propose around 3 inches of blanket minimum plus 2-3 inches of perl/verm concrete mix. 48 hour cooking would be great. I plan to build a really tight fitting door using some 2 inch ceramic insulating board that I have left over with Walnut decorative fittings. Hopefully the insulating board will keep the heat away from the Walnut! and I will be able to seal the dome really well.

Brad

[RTflorida]

Vermiculite vs. perlite.....I used both, verm. for the insulating slab and perlite for the dome; as for workability and consistency of the mix I don't have a preference.
The only thing I found different was the "dry, out of the bag" consistency. The perlite granules were of a more consistent size all the way through each bag. The vermiculite seemed to be about 25% dust - at the bottom of each bag; as Les put it - seemed like very fine sawdust, I guess he found the same to be true. I would definitely recommend getting the course grade (if you can find it) as opposed to the medium (which I used) horticultural grade.

RT

[Derocherconstruction]

I used 2" of the Forno Bravo insulation, then 2" - 3 " of vermiculite/portland mix, then 2 layers of stucco. Seems to be very waterproof so far, I cooked 12 pizza's in a great rainstorm thursday eve, no problems. The outer dome doesnt feel warm for hours with the insulation that I used, and holds the heat for a whole day for cooking. We are still experimenting, but we've cooked about 85 pizza's since the 4th of July, with a few other attempts at a few other things... Bottom line - the ceramic insulation will make or break the project, more is better, 2 layers of the 1 inch is working great, double would be the best I'm guessing.....Good Luck, Jim

[plowry]

Originally Posted by Derocherconstruction

I used 2" of the Forno Bravo insulation, then 2" - 3 " of vermiculite/portland mix, then 2 layers of stucco. Seems to be very waterproof so far, I cooked 12 pizza's in a great rainstorm thursday eve, no problems. The outer dome doesnt feel warm for hours with the insulation that I used, and holds the heat for a whole day for cooking. We are still experimenting, but we've cooked about 85 pizza's since the 4th of July, with a few other attempts at a few other things... Bottom line - the ceramic insulation will make or break the project, more is better, 2 layers of the 1 inch is working great, double would be the best I'm guessing.....Good Luck, Jim

I am using a ceramic blanket in conjuction with coal ash in walls (Rado uses coal ash) so what steps do I take to cover the blanket with coal ash so that it will not pack the blanket down and could I then cover the blanket/coal ash with stucco. Is stucco waterproof enough for an oven and what is the ingredients and mix.

[dmun]

Coal ash? Isn't that a heavy dirt-consistency substance? I have heard of using wood ash, which is at least light and fluffy as long as you keep it absolutely, completely dry, but coal ash? Seems like more thermal mass to me.

[Derocherconstruction]

I don't know what coal ash is either Plowry. The vermiculite/portland mix is light though, and it was put on over the insulation..... 2" of fb ceramic insulation, then chicken wire over the insulation, then the vermiculite/portland mix. There are several different mixtures for the outer stucco mix if you search the forum, depending on the area you are from, and the local ingredients available. I see you are from Australia, so maybe someone in your area will have a local recipe with local ingredients/techniques.. Vermiculite is very reasonably priced here in Michigan, as is the portland cement. These worked well for me... Jim

[RTflorida]

Juste googled coal ash and read several articles.
What I found:
1) By product of coal burning (mainly from power plants)
2) Can contain any/ or all of the following - limestone, aluminum, silica, clay.
3) Generally contains heavy metals, selenium, arsenic, mercury - and very likely in high concentrations.
4) 3 basic types: Fly Ash - the finest (like dust), can be used as a portland substitue in concrete, bonds well and adds strength. Bottom Ash - has a sand like consistancy and can be used as a sand substitue in construction. Boiler Ash - coarser than Botton Ash, used in asphalt roof shingles, snow/ice control on roads, sandblasting grit, and asphalt for roadways.

Not sure why Rado would be using this stuff, other than an over abundance in his local area...not to mention, I found nothing that recommends it as an insulator. I think portland, sand, perlite, and vemiculite are much easier to locate for most oven builders - based on EPA regulations, I don't think this stuff is readily available in the US to people outside of industry.

RT