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BrritSki 08-12-2008 01:49 AM

Expanded clay insulation OK ?
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As I mentioned in my build thread, I ran short of vermiculite when pouring the under-hearth insulation layer, so made sure the edges were level where the dome needs support and just left a small depression in the centre to fill later.

Unfortunately I was unable to source any more vermiculite and all the builders merchants are now closed for 2 weeks, so instead I bought a bag of "Expanded Clay" (see attached photo) which I was told would be suitable.

These are very light but hard irregular granules averaging about half an inch in diameter. I mixed them in a similar way to vermicucrete and poured them into depression. They were quite hard to level having such big chunks, but I left them below the level required and then finished off with a thin skim of concrete that the firebrick base will rest on.

Although this was not ideal for the base, it would be very easy to slap on in handfuls to insulate the dome, but I wondered if anyone had any experience of using this material and knew its insulation properties ?

Thanks in advance for any help Roger

Frances 08-12-2008 02:12 AM

Re: Expanded clay insulation OK ?
As far as I know you're on fairly new ground there. I think Dvonk used something similar, there's some discussion of it on this thread:

Have you tried heating up that chunk you've got there? Hold a blow torch to it and see how far the heat spreads.

BrritSki 08-12-2008 02:28 AM

Re: Expanded clay insulation OK ?
Thanks for that link Frances. I had done a search for "expanded clay" but it came up with nothing, so it must have been my "typink skils" again :(

I'll give it a try with a blow-torch, nice idea !

Ciao Rog

egalecki 08-12-2008 06:34 AM

Re: Expanded clay insulation OK ?
That's some interesting-looking stuff there. How did the blowtorch test go?

BrritSki 08-12-2008 09:23 AM

Re: Expanded clay insulation OK ?
Haven't done the blow-torch test yet, priority today was getting other stuff done - see my other thread which will be updated with today's progress in a few minutes...

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