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Old 07-14-2014, 01:46 AM
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Location: Majuro, Marshall Islands
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Default Homemade insulative refractrory

Hello,

I am writing from the Marshall Islands and while I dream of a brick oven and even bought and stored fire bricks my first steps are even more simple. On atolls here we have coral sand, coral rock, and coral reef. Very simply there is nothing else unless it is imported. We do have portland cement and we can make "concrete" from coral. This stuff has almost no fire resistance.
I need background information and direction. Anything and everything. As my first post I do not even know what section to address. I have been reading and picked up some things. Some say fireclay, none here. Then some said bentonite clay none here. Then some one said Kitty litter. That is here.
I also read some where that mortar cement is more heat resistant than concrete, then I heard there is type N and type S. Actually my first efforts are probably be aimed at a 5 gallon rocket stove. I would want to try an make a mix of mortar cement perlite and kitty litter. Hope some one can help
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Old 07-15-2014, 06:52 PM
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Location: Townsville, Nth Queensland,Australia
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Default Re: Homemade insulative refractrory

If I were in your position I'd try a mix of crushed coral(nothing bigger than about 6mm down to dust). Coral is full of holes that will trap air and work as insulation. Try to select corals that are really light in weight because these will contain more air. Not sure about corals refractory properties, but you can start with a small project to see how it goes. If you use it for insulation it doesn't have to be particularly refractory as once it's away from the flame it won't get too hot anyway.
I'd be trying a 3:1:1:1 mix of sand,cement, lime, clay for the dense hot face refractory.
and 5:1 crushed coral, cement for the insulation layer under the floor
and 8:1 crushed coral, cement over the oven dome. If using beach sand wash it well to remove the salt first.
A good cheap source of clay is bricklayers clay. If that is in available you may have some ants nests or failing that try digging for a layer of clay.
cobblerdave likes this.

Last edited by david s; 07-15-2014 at 06:55 PM.
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Old 07-15-2014, 09:50 PM
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Location: Majuro, Marshall Islands
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Default Re: Homemade insulative refractrory

David
Thanks for the start. Coral has horrible properties relative to fires.

There is no clay in the Marshall Islands there is fine coral dust coral sand and coral rock. If I have a heat resistant good elbow or form I could consider a mix of coral beach sand as insulation around the outside
Sand here is pieces of porous coral,foramenifera and Coraline algae, It may be fair to middling as insulation. However I also have access to both perlite and vermiculite.

With no clay I was looking at kitty litter (bentonite clay). This comes in small
granules. Does it have to be pulverized o powder or can I mix with perlite as is? I am ;looking at mortar (premixed with lime and sand) and perlite and kitty litter. say 2 1 1 . this is all in the thinking learning stages
Thanks

Enemanet
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Old 07-16-2014, 03:56 AM
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Default Re: Homemade insulative refractrory

G'day
A lot of kitty litter is bentonite clay so that could be a source of clay on coral atolls. Like Davids mentioned you don't need fireclay as such, the refractory arnt needed at the temperature of a WFO. But clay works well at making the mortar " plastic" and sticky and easy to work with.
Regards dave
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Old 07-16-2014, 06:17 AM
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Join Date: Aug 2012
Location: Wisconsin
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Default Re: Homemade insulative refractrory

It sounds very challenging to have few materials to select from! This is not from any personal experience, so take it as such, but perhaps you could use the ideas that Dave and David S are suggesting as an insulating base, then use your firebrick in a loose stacked configuration. I think I may have seen an example at PizzaMaking.com - Pizza Making, Pizza Recipes, and More!, but I can't find the exact forum discussion right now, but it uses angle iron to support the bricks across the top. I suspect the life is limited, but it might get you something to bake in while finding other materials. Just a thought... Good luck! Carl
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Old 07-16-2014, 01:28 PM
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Default Re: Homemade insulative refractrory

Quote:
Coral has horrible properties relative to fires
I would agree. Since coral was at one time a living marine organism, it has a propensity to decay (and calcify) with other marine shells and sedimentary rock, resulting in limestone (calcium carbonate).

Since you have access to firebrick, you have a source of fired clay, albeit you will have to salvage the dregs from your saw or crush it by some other means. The procurement of hydrated lime would go a long way towards making an acceptable refractory mortar.

Regarding a homemade insulation, you might try mixing a refractory mortar with ordinary wood sawdust. Once in place, as the sawdust heats up and burns, it leaves tiny insulating holes. Coral may behave in the same manner.
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Old 07-16-2014, 05:42 PM
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Default Re: Homemade insulative refractrory

G'day
Without going and and buying some cat litter and experimenting myself , I would pulverize it and the soak it in water to hydrate to make it break down further.
Remember its in the homebrew mortar to make it easier to handle and help it stick to the firebrick. You don't require it in the insulation layer.
Of you have access to pearlite you only require Portland cement to bind it . Under the hearth 1 Portland to 5 pearlite and a lighter mix on the dome proper say 1 Portland to 8 to 10 pearlite.
As GianniFocaccia pointed out the local sand is basically the remains of corals and small sea organism. A source of lime. In our local area a hundred years ago lime was made by burning the shells of the local oysters. I'm afraid that under heat this might happen in your oven and the sand might turn to quick lime? I'm be no means an expert but I think that it would mean more investigation.
You might have to buy in the sand as well
Anyway just some thoughts
Regards dave
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Old 07-18-2014, 03:43 AM
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Default Re: Homemade insulative refractrory

Thanks for the responses, I am going to think on them and answer back later
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