#11  
Old 01-29-2011, 12:35 AM
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Default Re: Tanzania/Canada

Perlite is an alternative insulating material to vermiculite if it is available to you. I have also heard that manure can be used successfully as an insulating material. I think it is mixed with cement around 10:1 Presumably manure with a high undigested fibre content like dried horse manure. We live in a hot climate, usually 20 C min. 30 C max and I think in our climate you don't need quite so much insulation. We often get a bit annoyed because we have to wait until about 11 pm, with the oven door off, to get the oven temp down enough to bake bread or pastry desserts. We are currently waiting for an approaching cyclone to clobber us. It comes with the territory for living in the tropics.
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  #12  
Old 01-29-2011, 12:39 AM
david s's Avatar
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Default Re: Tanzania/Canada

Steve,
You may also be interested in Rocket stoves. They are amazingly efficient and ideal for third world communities. Do a google search, there is plenty of info. Only need a few sticks.
Dave
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  #13  
Old 01-29-2011, 10:35 AM
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Default Re: Tanzania/Canada

Steve,
I have neighbors with cob WFOs they have no insulation like the high tech stuff most of us here have in our WFOs. That being said they manage to pull off a single bake of bread without problem. I never have seen them try to do a second bake and suspect it might be problematic, but perhaps not. However, a single bake is all they require so it fits their purposes well.

Also, (and this is something very much (IMHO) worth taking into consideration) how easy is it to get wood for the proposed WFO? Where I live wood is no problem nor is it for my neighbors. It's free save for the cost in labor to cut and split. So the fact that my neighbors cannot bake using the saved heat the following day is of little concern. But where you are building this WFO is wood freely available or like many places here in the US you have to pay for it, or have it brought in?

If it is the latter, then perhaps figuring away to insulate the proposed WFO would probably be worth the hassle.

Hope this helps,
Wiley
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  #14  
Old 01-29-2011, 11:17 AM
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Default Re: Tanzania/Canada

Mud used in a cob oven is actually a pretty good insulator. A friend who built a.mud brick house up here in the tropics has a home that is so cool you'd swear it was air-conditioned.
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  #15  
Old 01-30-2011, 12:56 PM
Peasant
 
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Location: Canada/Tanzania
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Default Re: Tanzania/Canada

Hello All,

It's been a week since my last post and I thought I would share an update and some photos. Construction was delayed until mid week as a number of emergency repairs cropped up that needed tending to.
For the most part we were able to work on each component of the hearth/stand every day since Wednesday.
Wed.-footings and floor
Thurs.-walls
Fri.-arch over opening
Sat.-hearth
After every step we have continually kept the concrete/mortar moist for slower curing resulting in hopefully a harder finished product.
Tomorrow we install our insulation layer on the hearth, wherein lies my next question. I have read about the different ingrediants to mix with the concrete. I haven't had any success to date finding any vermiculite or perlite. In the a.m. I am going to a nearby dutch rose growing facility to see if I can get a little of either. Failing that, a local brickmaker suggested that I might try rice husks
He uses them when he fires his bricks. I know that it is a different application but I thought that it might give the cement the volume necessary to give it insulative value.
I do have some stryafoam in the shipping container we use for storage. Didn't know if I could break it up and use that?
As usual thanks for any advice anyone can pass along and I hope everyone enjoys the photos.

SteveS
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  #16  
Old 01-30-2011, 04:38 PM
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Default Re: Tanzania/Canada

I would avoid organics if at all possible. They will burn and stink. Bricks are a different story: they are fired hot enough to completely burn out the sawdust. Both vermiculite and perlite are expanded minerals. And styrofoam? Don't do it. Your oven will smell of burnt plastic for all eternity.
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  #17  
Old 01-31-2011, 06:17 AM
Peasant
 
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Default Re: Tanzania/Canada

Hello from Tanzania again. I spent most of the day trying to scope out vermiculite or perlite. No luck, other than an agricultural supply store that I frequent which had brought in an order of vermiculite a couple of weeks ago from South Africa which has already been picked up by the farmer. Sooooo.....I was thinking about what these two products actually do when they are mixed with cement. Is it the porous nature of these two products creating tiny air pockets within the 3" layer of concrete that actually give it the insulating value, the material itself, or a combination of the two?
I can certainly find dry cattle manure here to use or I was thinking of a very porous, light volcanic aggregate that is available here. They make cheap, light weight cement blocks from this material.

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Old 01-31-2011, 09:32 AM
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Default Re: Tanzania/Canada

Steve,
That light porous aggregate looks a great deal like pumice. My bet is that it is pumice. It would work well although I would use as little portland type cement as possible as binder. Use like perlite to make perlcrete.

Hope this helps,
Wiley
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  #19  
Old 01-31-2011, 09:56 AM
Peasant
 
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Default Re: Tanzania/Canada

It Helps a lot Wiley! What do you think of daves suggestion of dry manure added in as well?

Steve.
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  #20  
Old 01-31-2011, 09:59 AM
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Default Re: Tanzania/Canada

Pumice is a good choice. Manure is not. Organics will burn and stink.
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