Combine Mortars

[fxpose]

Re: Combine Mortars

I am in New Zealand and have just started the hearth. I notice that you have a medium under your fire brick. what is it.

One of the most important components of the build: Insulation

[kriso]

Re: Combine Mortars

George
What type of insulation is it. It looks like Hebal? Someone told me you can use this???
Kris

[dmun]

Re: Combine Mortars

I read lots of people swear by the home brew, is that just because it is cheaper, or just easier to get?

There seems to be a slightly less frequency of cracking with the homebrew mortar. And yes, it is cheaper and easier to get in some places.

I used heat-stop and got lots of cracks, but much of that may be a result of my thin-wall construction.

[fxpose]

Re: Combine Mortars

George
What type of insulation is it. It looks like Hebal? Someone told me you can use this???
Kris

Hi, I'm not sure whose oven you're referring to but on my build I used a 3 inch thick ceramic board.

[azpizzanut]

Re: Combine Mortars

Hello Kriso,

Your question about Hebal made me curious about it. They have a website that provides some information about their insulating construction/building products.
Environmental Implications Hearth insulation is generally a low density refractory product. I didn't see anything like that listed in their product guide.

Search Hebal on this forum for some interesting information.

It is easy to make your own insulation from cement and perlite or vermiculite. Many recommend perlite mixed 5 parts to 1 part Portland cement. That is what I recently used for my oven. If you decide to make your own hearth insulation you will want to read the package label and avoid perlite with silicone added. Silicone makes it easy to pour perlite into voids of building blocks but it complicates bonding water and cement to the perlite. Properly done, the mix will harden. Even though you may have your doubts, it will support the weight of a fire brick hearth.

Hebal panel blocks were successfully used for oven construction but it doesn't appear to be suitable for hearth insulation.

Cheers,

[kriso]

Re: Combine Mortars

Thanks for that info, I will read the link you have added, I think I will give it a go and make my own, I have a cost of $97.00 for a 100 litre bag of vermiculite (here in New Zealand). That seems to be the cheapest I can find so far.
Thanks again for the info.
Cheers

[azpizzanut]

Re: Combine Mortars

Kriso,

Perlite is mined and processed in several locations in NEW ZEALAND. You might be able to locate a lower price for your perlite needs by locating the processor.

NZ dollars are roughly 3/4 the value of a USD. I recently bought 4 cu ft perlite for my project (113.2 cu litres) for $33.40 USD. It is hard to imagine perlite priced at nearly $1 NZ per litre.

Interestingly, perlite is processed near my home but the factory does not sell to individuals. The product is sold in bulk to commercial businesses or industry for packaging and distribution.

As a reminder, perlite comes in several grades. You want horticultural grade (used for potting soil/gardens). Commercial grade is also acceptable if it does not have silicone added.

Cheers,

[david s]

Re: Combine Mortars

azzpizzanut,
I used Hebel as an insulator under the floor of a mobile oven and it has worked ok.I would disagree about it's suitability for use in building the dome though. It is after all Portland cement, aggregate and air. At high temps and direct flame impingement I wouldn't rely on it's longevity.

[azpizzanut]

Re: Combine Mortars

Hi David s,

I agree with you about the lack of suitability of Hebal for dome construction for the reasons you stated. A builder who used Hebal said he was happy with his oven. Maybe what he doesn't know isn't hurting him.

Regards,

[david s]

Re: Combine Mortars

It might be ok for an insulation layer but not for the hot face. Apart from the Portland cement issue, it is full of air and not dense where you need density for heat storage.
Dave