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connie kokiousis 10-08-2008 11:49 AM

mortar and insulation mistakes-help?
I'm disappointed today to discover that my insulating hearth of vermiculite-concrete turned out to be 3" not 4". I don't know why I didn't check this before we went on to the dome, but the dome is done now.

How much will this affect the oven temps?

We grouted the interior gaps with the fireclay-portland cement-lime recipe, which I think was a mistake, was it?

And finally, I have a 36" interior dome, will two layers of FB blanket be enough insulation on the dome, with stucco on top of the blanket?


james 10-08-2008 12:14 PM

Re: mortar and insulation mistakes-help?
Hi Connie,

Oooops on the vermiculite concrete. I think it will be fine -- you might lose a little heat out the bottom, but nothing serious. Nothing to worry about.

Try to make sure you do enough overlaps with the FB Blanket where you get 3" around the dome. Two boxes should do that on a 36" oven. If it is tight on material, make the insulation thicker on top of the oven than on the sides.

You'll be fine!

connie kokiousis 10-08-2008 12:51 PM

Re: mortar and insulation mistakes-help?
Thanks for the answer James. I did order two boxes. If there are any scraps I will lay them on top.

What do you think about the mortar inside the dome, is it ok that we grouted the inside?

One more question, do you know where to get a temperature gauge to install?

Thanks for all the great advise, I have spent hours and hours reading all the postings in the forum and looking at photos.

I will post some of my photos too.

connie kokiousis 10-08-2008 01:42 PM

Re: mortar and insulation mistakes-help?
3 Attachment(s)
I have tried to attach some thumbnails of my progress so far. We are getting excited about this project. Should be finished in a week and will post more photos.

james 10-08-2008 03:58 PM

Re: mortar and insulation mistakes-help?
Hi Connie,

Your oven looks great. Way to go.

Mortar inside the dome is fine -- some builders like to keep it nice and clean, as you do see the brickwork when the oven dome goes clear when it is fully fired. Your call. But joints facing into the oven are fine.

Are you installing one thermocouple of two?

This is a good question -- particularly if you are installing just one. What does everyone thing. 2" in from the inside face of the cooking floor, or the dome at the apex?

If you are doing two, then I would go for those two spots.

Are folks happy with setting the thermocouples 2" back from the face of the oven?


masuzzu 10-08-2008 08:42 PM

Re: mortar and insulation mistakes-help?
How is the thermocouple installed?
Is it drilled into the brick or can it be mortared in the gaps?


connie kokiousis 10-09-2008 07:46 AM

Re: mortar and insulation mistakes-help?
I don't even have a thermocouple yet and I don't know where to get them. Can I drill a small hole to install them before I apply the insulation? Should I use some mortar to close the gap or some furnace sealant?


CanuckJim 10-09-2008 10:55 AM

Re: mortar and insulation mistakes-help?
James, et al,

I installed mine to within 1 inch of the cooking floor, same for the dome. The wires should be drilled into the brick from the back. You can seal the holes with mortar or furnace cement in a tube (same gun as window caulking). Go to Sensors, Thermocouple, PLC, Operator Interface, Data Acquisition, RTD to find out about thermocouples and order online. No affiliation with those guys, though; it's just a convenient spot. Alternately, find a pottery/kiln supplier in your area.


dbhansen 10-09-2008 11:06 AM

Re: mortar and insulation mistakes-help?
Connie, you should probably be aware of the other temperature gauging options. The thermocouples are somewhat expensive and then you'll also need something to "read" them (something to display the temperature), so it could end up costing at least $200+. And you'll need to route the wires.

Another option is a simple self-standing dial thermometer, but that will only gauge the air temp where it's sitting, and you'll need one that reads up to 1,100+ degrees F. And another option is an infrared thermometer, which looks like a gun that you point into the oven when you want to gauge the surface temperature. Many folks on this forum use nothing but an IR thermometer, since you can point it wherever you want. FornoBravo sells a nice one. You can also find models that are a combination IR thermometer and thermocouple reader in one.

But the only way to gauge the internal temp of your bricks is with a thermocouple. These can be placed in the floor bricks, in the air within the dome, in the dome bricks, outside the dome bricks (under the insulation), etc. Hope that helps.

Yes, you can drill a small hole to install them, or insert them into a layer of mortar between bricks. If the hole is tight, I don't think there's a need to mortar them in place.

diy 10-09-2008 03:21 PM

Re: mortar and insulation mistakes-help?
You can buy high quality refractory mortar for setting firebricks or

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