#11  
Old 07-14-2006, 08:12 AM
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Oh yeah river rock can explode. In an earlier life I used to be a fire tender at a sweat lodge. Our volcanic rock was getting a bit small and someone brought these nice boulders to use. I sratched my head and said sure why not. We used a wood and gas fire combination stacked the rocks and then put a metal funnel shaped dome over the lot. About 3 hours later some of the rocks split and one or two dented the funnel.

So as long as your rock is insulated from the heat you should be ok.

If they are not going to be isolated from the heat and yu have doubts then build yourself a roaring fire and let them cook for four hours.
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  #12  
Old 07-14-2006, 08:21 AM
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Default Consistent terms

(RBN) "I'm building my oven base out of them".

(M) If by "base" you mean the Hearth Stand that is usually made of re-bar supported hollow core concrete blocks, I think you have no reason to worry.

(M) If you plan to use river rock as a part of your Hearth Slab I'd be more concerned. I can only imagine using large river rocks as an aggregate for a refractory concrete that supports your medium duty fire brick. While I applaud your ecologically friendly commitment, I worry that your oven may suffer if you become so dedicated that you apply the wrong materials.

(M) Several of us have been in the process of re-writing the plans for the Pompeii oven and want to release it in .pdf format. I hope to convince my colleagues to use the following nomenclature so that Newbies will have an unequivocally clear understanding of each term.

(M) Starting from ground level and working up, I'd like to see the following terms applied:

1- Foundation Slab: a Horizontal poured, re-bar strengthened conventional concrete on which everything else is supported. In some freeze areas, an added footing may be advisable

2- Hearth Stand: concrete cored rectangular blocks that form the perimeter structure that raises the business end of the oven to a comfortable height.

3- Hearth Refractory Slab: This slab is in 2 parts and the order of their placement is still a subject of debate that depends upon whether the builder wants to stress pizza, or bread baking. The traditional order has the lower layer a mix of perlite or vermiculite plus cement and water. The top layer is closer to a conventional concrete and contains a network of steel re-bar. It, or the perlcrete-vermicrete will support the actual floor bricks.

4- Firebrick Cooking Floor: These bricks are typically comprised of a high (up to 35%) Alumina content and are set on top of a thin, none adhesive layer of sand and fire-clay. The bricks radiate heat well and are resistant to cracking and spalling.

5- Firebrick Dome: The igloo of individual bricks that both retain heat and reflect it onto whatever food is being cooked.

6- Refractory Cladding: A crack resistent mortar applied over the dome bricks to help strengthen the dome and add some additional mass for heat storage.

7- Insulating mortar: Depending upon whether the builder wants to build a decorative enclosure, s/he may apply a layer of varying thickness Perlcrete or Vermicrete over the dome. The mixture is typically made with cement and either vermiculite or perlite in a ratio of 6 - 8 parts perlite-vermiculite to 1 part of cement.

8- Housing: A shell that protects the dome from the elephants. It can be made from many different materials but is generally made from cement board which can later be embellished with other more decorative materials.

There are many variations and optional material additions such as aluminum foil. I just wanted to suggest a consistent terminology and am taking this posting as an opportunity to suggest some terms to the 5 other editors.

Ciao,

Marcel
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  #13  
Old 07-14-2006, 01:13 PM
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Hey marcel no sneak peak at the Glossary ;-)

Item 3 will be revised to follow the Italian norm of convention which is to use the reinforced concrete as the bottom layer (which is a mixture of aggregate, sand, cement and water that was needed for a chemical reaction to get the matrix to bond that was subsequently de-hydrated in the natural curing process) topped with the insulating layer of perlite or vermiculite mixed in a 6 to 1 with cement ratio to from the insulating concrete layer upon which your oven floor and dome will there upon find rest. (was that a run on sentence?)

and 5 which needs to be told that the same bricks you use in 4 are used in 5.

marcel is right as I was beating around the bush in my first post. The river rock can be used as a facade to hide or beautify the Hearth Stand. Do not use it in your refractory slab - pop goes the weasel.
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  #14  
Old 07-14-2006, 05:52 PM
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Default no explosivo.

Yup, no worries. The river rocks are being used for the hearth stand, nothing else. Everything else is being done more or less to the plans provided here. Thankyou. I'm using cinder block for the interior of my stand walls, the river rock is pure pretty.
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Old 07-17-2006, 12:29 PM
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Quote:
Originally Posted by redbricknick
Yup, no worries. The river rocks are being used for the hearth stand, nothing else. Everything else is being done more or less to the plans provided here. Thankyou. I'm using cinder block for the interior of my stand walls, the river rock is pure pretty.
I am using a lot of river rock for my wall but the rocks are insulated from the heat with a Calcium Silicate board which assures a thermal break between the oven and the supporting structure. This sure is a fun project. I am ready to go out and get more rocks now though, I am running low.
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  #16  
Old 07-19-2006, 05:40 PM
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Default hearth form

I'm getting ready to pour my hearth, and am considering leaving the bottom of it in. If I used cement board in lieu of ply, i could just leave it in, correct? Should I use insulation board of some kind? I'm thinking about whacking a bunch of Galvanised screws through the bottom before I pour so it bonds better. I'll have photos as soon as we've capped the HEARTH STAND. Cheers, Nick

Last edited by redbricknick; 07-19-2006 at 09:16 PM.
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  #17  
Old 07-20-2006, 07:09 AM
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Yes you can leave the cement board in place. Make sure you support the cement board as it does not have the strength that plywood has. Not a bad idea to run some galvanized screws in there to help bond to the cement.
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  #18  
Old 11-01-2006, 11:39 AM
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Default Gosh dome it!

So. I'm at the point where I have to tackle the dome. I have a few considerations with regards to method. The vein method seems like the no brainer, no painer method, though I am considering building it free standing for a couple of reasons. The first is the company I would be in. Was the duomo built without forms? Is it the true mason's method? I'm all for innovation, but tradition is very important to me as well. If I ran a piece of string with a tennis ball from the center of the hearth and ensured it touched the center of each dome brick, would I not get a perfect hemisphere? The second reason is to make a tight looking dome. Is it not easier to regulate the tightness and cleanliness of the dome brick joins with no forms obstruct view and hand access? What of the wire method? I can't find the thread that post is in.

O.K. Now. The opening. I want to do the arch method. It seems that a few on this forum have tried and failed, others pulling it off. Of those who arched and won, who would do it differently if they could turn back the clock? Is it worth the agonising brick cuts which are involved?

Cast refractory vent pieces. Do I need to fire them as Drake Remoray did? Did the N.Z oven guy fire his?

So many questions. This is an invaluable forum, and I thank everyone profusely.
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  #19  
Old 11-01-2006, 01:00 PM
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Default The wire method

I can't seem to find the original post either but they talk about it in this link.

http://www.fornobravo.com/forum/show...ighlight=trick (Alabama oven)

In regard to the arch - I'd go for it. There are so many built, I can't believe that it would be that difficult.

Good luck!

Les...
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  #20  
Old 11-01-2006, 09:11 PM
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Default arch opening

Brick, I made my arch opening using a simple form from just 1/2 cut bricks. I cut some dome bricks to match them up to the arch better as I was going but really it wasn't a big deal. I took the "just start making it" approach. I ended up flaring the dome slightly to meet the arch because the arch was built perpendicular to the hearth but the dome starts to tilt away from the arch. I scratched my head about it a few times while doing it but I just put it together and it works. Maybe others have some wisdom about how to handle the transition but I think that's the way to do it.

The wire trick uses wire instead of string and a tennis ball. The advantage of a wire is it should be easier to position the wire in place and have it stay. Unless you are always working on the arch with a companion you really need your hands free. I used shims instead of wire or string but did not use a form for the dome. When you get to the higher levels of the dome gravity is really pulling on you until you complete each chain and the tennis ball could be really inconvenient. Maybe a pingpong ball on the end of the wire if you really want a sphere?

And I built up my vent with bricks and mortar so I don't know about casting. I think the issue with firing it depends on the refractory material you use - if it is heat curing then fire it, otherwise it can just be cast.
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