#11  
Old 03-21-2012, 05:28 AM
david s's Avatar
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Default Re: Hearth insulation

I think you are correct in your assumption that there would be little difference in refractory properties of the two materials as they both use portland cement.
From a practical standpoint I have used Hebel (manufactured by CSR) as floor insulation in a few ovens, although short of demolishing them can't tell how the stuff is standing up. I also used Hebel (75mm thick reinforced with 5mm steel cast into the centre, they call this stuff "Power Panel") as both the supporting slab and insulating layer under the floor of my mobile oven. I did it this way in an effort to reduce weight.Because this is visible from underneath where it sits in a steel cradle supported by 4mm flat bar with spacings of 1 ft. It is evident that there are some large cracks.I do not know if the cracks were caused by the Hebel being weakened by the heat or whether it was going over a speed bump at speed after I forgot that I was towing an oven (oops, no shocks)
End result though is that I don't believe the stuff is as strong or heat resistant as they claim. Vermicrete for me and it's cheaper.

Last edited by david s; 03-21-2012 at 05:30 AM.
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  #12  
Old 03-24-2012, 01:37 AM
cobblerdave's Avatar
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Default Re: Hearth insulation

Gudday
I've used "hebel' as hearth insulation in my oven. Mainly it was cheap ( I as given 1/2 of it) and was a lot more avaliable than pearlite or FB board at the time. Its been about 18 months now with the hearth still being straight and true and yes I have put a straight edge across it.
I have played with the hebel before and made ugly "stone" garden carvings carved wall panels and the like with a friend. You can saw it, rasp it, use power tools dremels etc but the one thing you have to be carefull with is if you take to it with a hammer and chisel. The wrong angle a bit to big a hit and you can crack it so easy. You have to watch it when transporting it and wrap it up carefully otherwise it will break in the boot of you car even on a small trip. No wonder it cracked on your trailer model Davids.
I can't see however that FB board or pearlite would put up with oven bouncing on them as there pretty soft and you can dent them with a finger nail.
I'm reluctant to pull up my hearth to check the condition of the Hebel so I can tell you its worked well for 18 months with no indication that is failling in any way. Ive also used it in an oven door which got cracked from dropping from the first couple of uses but it lasted till a month ago when I replaced it with a secound door also made of hebel.

Regards Dave

Last edited by cobblerdave; 03-24-2012 at 01:41 AM.
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  #13  
Old 03-24-2012, 04:11 PM
CvC CvC is offline
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Join Date: Mar 2012
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Default Re: Hearth insulation

Thanks Dave,

that was a really encouraging answer.
I´ve heard from a lot of people here in Germany that they´ve been using Hebel/Ytong for the insulation of the hearth, but I couldn´t get any information if it remained stable over a longer time.
What I was concerned about was the combined thermic/mechanical stress.

But in fact, the mechanical stress seems to be at least a dozen times smaller than Ytong/Hebel can take and I´ve found some measurements here on the forum that the temperature under the hearth is by far not as high as inside the oven, so I will give Ytong/Hebel a go.
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Old 04-09-2012, 04:43 AM
CvC CvC is offline
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Default Re: Hearth insulation

Hi there,

I found another variant of insulating material on the www, this is sold in Germany under the brand name "Poroton", I don´t know the brand name in the US, but this is often used here for insulating the hearth.

As it is made of clay, just like ordinary bricks, it should be able to cope with the temperature.

The insulating properties are pretty much the same as Hebel/Ytong (which are excellent) and it is cheap.

So it is proven to work, it is cheap and it is sold in every DIY-store here.
My stand is completed by now, tomorrow I will start building the hearth, I think will use Poroton.
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