Hi I am planning on building a pizza oven soon. Can you use insulation bricks under the fire bricks in the Hearth. I live in Thailand and am having difficulty finding vermiculite or Perlite, Isol, Laowool, Insulfrax etc... I have located firebricks, morter and industrial insulation bricks. I have read that Pumice may be used as an alternative. Has anyone tried this?
Light weight, porous bricks should help to insulate.
"Can you use insulation bricks under the fire bricks in the Hearth."
(M) I know nothing about the insulating properties of pumice but I'm sure that if you used the lightest weight, most porous bricks you could find that they would help to keep the refractory heavy hearth brick floor heat from wicking into the supporting hearth slab.
(M) I pasted the blurb below from the original Forno Bravo plans located at:
(M) Remember to adjust the height of your block stand to accomodate any change in floor height from what you hope to realize as a working height for your oven opening.
Insulating fire brick. These light-weight refractory bricks are designed to stop heat, and as such have low conduction and low heating holding capacity. They are often used to insulate industrial equipment. A typical insulating fire brick weighs about 2 lbs, compared with an 8 lb light duty fire brick.
Insulating bricks would make a wonderful insulation layer under and around an oven. One 3 inch layer on the inside of a ceramic kiln allows the inside of the kiln to heat up to red to orange heat, while only a couple of hundred degrees on the outside. The reason they are not used for this is that they are very expensive and have to be cut to fit the dome like the inside bricks.
If you can't get vermiculite or pearlite, volcanic pumice should work fine. It's what the ancient romans used, after all.
Thanks guys looking fwd to making some high temp NY style pizza. I've got just the spot for an oven in my back yard!! I have a few other projects on the go but as soon as I tidy them up it will be jumping into igloo ovens.
Insulating fire bricks.
A guy at a special effects company offered me a bunch of these. I figured I had no use for them. They are still sitting in his warehouse.
He shoots, he scores
That's it. That could be your scrounged under oven insulating layer. I have never done research into the efficiency of insulating firebrick, though I can ask around and can find out more.
If they are free, you can stack up a couple of layers of those under your oven.
I have always though of insulating firebricks and regular firebricks pumped full of air. They are made of the same basic refractories (alumina and silica) are a regular firebrick, so they can withstand the stand high temperature, but then rather than absorbing heat, the air holes block it. An insulating firebrick weighs a fraction of a regular low or medium duty firebrick.
Beammeup -- if you can't find insulating firebricks, or they are really expensive, pumice is a good alternative. If you really strike out, you can always use sand. We don't recommend it, but if it's your only choice, it will work in a pinch.
The really good insulating bricks/tiles are found at NASA - get a load of of the castoffs. "Jewelers no longer have to worry about inhaling dangerous asbestos
fibers from the blocks they use as soldering bases. Space Shuttle
heat-shield tiles offer jewelers a safer soldering base with
temperature resistance far beyond the 1,400 degrees Fahrenheit
generated by the jeweler's torch."
They used to be made by Rockwell but have been bought by Vought Aircraft Ind.
I have found some vermiculite in Thailand, at a horticulture place. They sell it for around $35.00 for 4 cu ft. Is that expensive? How many bags for a 38" igloo oven at 4" for base and cover? I have also contacted a chap in Northern Thailand who made an oven. He used slowly burned rice hulls, or husks. He says they make a great insulation. They use that here for brick making kilns. I think I would prefer to use the Vermiculite if this price isnt too outragiuos.
I used 6 of the 4 cu ft bags of perlite for my 42" oven at 6" thickness. If you take a lot of time to close dead space in your oven you can reduce your amount to use. Perlite bags were $15 for 4 cu ft where I live, vermiculite was about $20. I bet you can use 4 bags, maybe less. One note on loose fill, close any gaps, no matter how tiny. Drake used the canned self expanding foam - a brilliant idea that I wish I had considered.
vermiculite & prosper...
I'm still studying the basics of this arcane craft, and am collecting prices from Australian suppliers. One firm has a materials list for a 100 cm round pizza oven and states you'll need three bags of vermiculite at $26.60 ea. plus 1 bag of ciment fondu at $40 for insulating this oven. It doesn't sound much, does it - the quantity, I mean. Perhaps they refer to the hearth part only?
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