Tanzania/Canada

[dmun]

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.

[SteveS]

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.

[Wiley]

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

[SteveS]

Re: Tanzania/Canada

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

Steve.

[dmun]

Re: Tanzania/Canada

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

[SteveS]

Re: Tanzania/Canada

Ok...thank-you both! Desision made....pumice it is!

Next 2 questions. 1. I can't get any refractory cement so I need to make my own. My brick supplier (whom I shall fondly refer to as The Brickman) suggests a blend of lime and sieved termite dung (which has been sun dried and fine granular in size) or his friend who apparently builds fireplaces locally uses a blend of 5 parts sand, 1 part lime, and 1/2 part cement. Any thoughts?

2. The bricks for the floor are good and hard however are designed to be split for decorative use thus have 3 small air pockets running lengthwise. A concern?

I've also included a picture of the oven layout using some brick pieces.

[Wiley]

Re: Tanzania/Canada

Steve,

I have no personal experience with refractory mortar (my dome is different than the usual brick WFOs found on forum). I would think, however, that if duplicate as closely as possible the "homebrew" mortar that is mentioned on the forum you would have the best chance of success.

Your local bricks look interesting. How were they fired? Do you have any idea of what temp they are fired at or to? Are they terracotta? Are they extruded or hand rammed in a mold? "Berrystreet" of the forum used bricks with holes in them to build his WFO and last I heard his oven was still functioning, although at the time of his construction there were people who said they wouldn't work.

Bests,
Wiley

[david s]

Re: Tanzania/Canada

If I were using the pumice I would smash it up to make the lumps smaller which will make it easier to apply. Try for grains no bigger than 5 mm. Course saw dust is another material often used by kiln builders as an insulator aggregate, but I guess it will also burn a bit and take ages to dry

[david s]

Re: Tanzania/Canada

Regarding your mortar, your best bet would be the poor mans mortar 3:1:1:1 fine sand, lime, fire clay, cement. If you cant access fireclay substitute with the anthill which is almost all clay anyway.

[SteveS]

Re: Tanzania/Canada

Just going to start the insulating layer this morning using the pumice cement mixture. Before I lay the oven floor the Pompei oven plans suggest a thin layer of mixed sand and fireclay (in my case sieved termite excrement) and water. In another Forno Bravo instruction pdf they suggested a thin layer of refractory. Just wondering if one would be better than the other considering the soft nature of the pumice having been mixed with a minimum amount of cement for the insulating layer below.

Also wondering if Tuscan or Nealopitan style would be preferred for our orphanage requirements. I really don't think pizza will be the primary food. Baking breads, muffins, cakes/cookies, cooking/roasting meats and vegetables, and water boiling will probably be more the primary uses.

Finally, I am planning about a 40"-42" inside diameter. Running thing on a budget here means I want to try to find the appropraite balance of size of the oven for the amount of food needed to be prepared with one fire vs. the amount of wood needed to bring the oven up to temp. I guess the question is how much more wood does it take to fire a 42" oven than a 36" oven?

[SteveS]

Re: Tanzania/Canada

Hey Wiley,

I'm having a hard time finding the "Berrystreet" post about the floor bricks with holes he used. I tried sending him a private message but his name isn't in the system. By the way is there a way to search a list of Forum members?

Cheers,
SteveS.

[Wiley]

Re: Tanzania/Canada

Steve,
OK here's a link that should take you to berryst's thread:

http://www.fornobravo.com/forum/f3/i...ioni-4420.html

I don't know what's going on but I tried finding it a few different ways. Seems there has been some expunging of the records. For example if you ask "search" for all the posts I have made they run out at the 500 mark, for me that is early February 2009. I checked there because I posted on his thread. Perhaps there's a limit to how many posts are kept. I joined Forno Bravo in early 2008 so there have been posts lost or deleted or ? <Rant deleted>

Anyway, I found the thread by scrolling thru the introductions.

Personally I would NOT use termite poop in such a location as you suggest (beneath the bricks). On of my other hobbies is letterpress printing and one of the stinkiest things that has happened to me was to fire up my Intertype linecaster without checking the pot (where the type/linometal is melted) for mouse poop. Mice like the pot because after the machine is turned off it remains hot, then warm for hours; they seem attracted to the warmth and leave their calling cards. Anyway all door and all windows were opened, the whole building evacuated and uninhabitable for most of the day (and this was in the winter). So my thoughts: no poop from any animal, insect, or creature is going to be deliberately placed/put/entered into or otherwise associated with my WFO, thank you very much.

Beyond that I would personally think a hemispherical WFO would give your WFO a larger range of items that can be baked than the lower domed WFO. Also I would think that having the higher/larger entrance would make repairs to the interior (should they be needed) easier to accomplish.

My WFO is 40" and I find it a good size from my needs. I use but a small portion of it's potential. There are arguments for larger and for smaller, I would think available supply of wood for firing the WFO would figure into your size decision.

Hope this helps,
Wiley

[david s]

Re: Tanzania/Canada

In Northern Australia traditional aboriginals use large anthills to make an oven. They dig out a hemisphere at ground level, light a fire in it, then use it as an oven just as we do.

[Laurentius]

Re: Tanzania/Canada

Are you buying the termite excrement or are they giving it to you?? I tried to research termite to see if it was used for anything and I found nothing, except that if was an indicator of the present of termites.

[david s]

Re: Tanzania/Canada

I don't think it is actually their excrement. My understanding of it is that they "mine" clay and process it with something they produce, so the content is mostly really fine particles of clay. In Australia it used to be used as a surface for tennis courts. Performed really well apparently.