Before pulling the trigger, in need of criticism

[neil2450]

Re: Before pulling the trigger, in need of criticism

Hello Giol

I would not use any wood that has any kind of stain or waterproofing on it to bun in your oven at any time. You never know what kind of chemicals or toxins it will give off.

Neil

[Gulf]

Re: What to burn for curing?

I got some old used-to-be stained pieces of wood that my wife used to support her climbing plants. I am thinking of using this as fuel for the curing phase. Do you think that whatever stain is left in them to make them waterproof, is going to create a problem to the oven?

I would not use it. There is no telling what the stain is made of. Think about any chemicals that have been applied to the plants. There should be plenty of options out there for a curing fuel without taking risks.

[giol]

Re: Before pulling the trigger, in need of criticism

You are right.
Just finished 1st course and cut a stainless steel arch for the door.

[giol]

Question about transition

I need your advice on the transition and vent i am thinking of.
I have a 20x10x2 inches firebrick i used as pizza stone on my bbq and i am thinking of laying this across the top of the opening.
I already have a stainless steel arch (18 wide x 11 high ). I am going to put some high temp mortar between this arch and the firebricks on the sides and lay the big firebrick on top of the peak of the arch. The big firebrick will be supported on its two edges on firebricks of the 3rd course and there will be mortar between it and the steel arch.
Now comes the difficult part : i want to cut out a rectangle (10x5) from inside the big firebrick. So the big firebrick becomes a frame/basis for the vent. This frame will be protruding over the opening without additional support on the two external corners.
Do you think the forces of the dome pressing down on the big firebrick will cause a problem or will it help support the protruding part?

[david s]

Re: Before pulling the trigger, in need of criticism

Can't give advice here except to say that cutting a rectangle out of the centre of a large firebrick will be difficult and lead to weakness at the inside corners. Not saying it wouldn't work, but if it does fail it will be hard to fix. There are some good solutions by other builders that I think would be more suitable, although if you think you can do it forge on. Love to see different solutions.

[giol]

Re: Before pulling the trigger, in need of criticism

I started going 45+ degrees today and i can see some triangles between firbricks.
I was wondering if i should fill this holes with the refractory mortar or should i fill them at the end with the castable insulating concrete which is less likely to crumble and fall.
I read somewhere in the forum (or maybe the pompei doc) that we should avoid the concrete bonding with the firebrick, why is that?

[david s]

Re: Before pulling the trigger, in need of criticism

I think they are better filled with dense stuff. Use your mortar and brick chips.

[giol]

Re: Before pulling the trigger, in need of criticism

Hello guys,
a lot of progress since last time. I have finished the oven and started the curing process. The dome seems to be very well insulated as the temperature is very near ambient, except for two points where the concrete has cracked (1 inch long ,thin like hair) and there i get higher temperatures. The foundation of the oven which is a metal table with 10 cm of insulation concrete on top is where it gets interesting.
It seems that a lot of water from the whole structure is actually pooling at the bottom of the table. It slips through the pores of the concrete and ends up there. I opened a few holes on the metal and i am blowing air inside to get the water out, but it is a long process. In two days i think i got some 10 liters out. This other interesting thing is that the water on the outline of the dome is not clear but it has ash inside. I think what happens is that the vapor exits the bricks and as it gets in contact with the outer insulating concrete it cools down to water and drips to the edges carrying with it some ash particles.
After the first 6 hours of firing the base of the table was amibient temp except for a small patch in the middle ,which is where the water has started pooling. Now there are more patches.
Anyway on after the 30 hours of slow curing i put some extra wood and the dome turned white (so i cooked some pizza anyway) then i stopped feeding it and let it rest. It is 12 hours later now and the oven is at 200 deg celsius without a proper door installed.
Any ideas about the cracks on the dome? I filled the crack as much as possible with a special fiberglass filler used for fireplaces. Should i use some refractory mortar on top of that? Is there any trick to insulate it? I am afraid that it will crack the render after i apply it.
Also the outside of the dome near the oven door gets hotter than the rest. Will the render hold there or will it crack?I want to finish it with mosaic tile on top of the render, as seen in many professional napolitan ovens, but i dont now how to deal with the heat coming out the door.

[cobblerdave]

Re: Before pulling the trigger, in need of criticism

Gudday
I would leave doing any sealing or any repairs for a month at least. Read the instruction on paints and sealers for concrete and renders they say to leave for a month to fully dry and cure
Regards dave

[david s]

Re: Before pulling the trigger, in need of criticism

I'm not surprised about the water dripping out of your oven. Last year I was firing a new (empty) kiln prior to using it. The recommended schedule was 50 C / hr up to service operating temperature. Water began dripping out from the base at about 300 C and didn't stop until over 400 C It is the water being pushed out by the heat inside, condensing on the steel liner and running down to find its way out from the base somewhere.
Regarding your worry about the mosaic on your outer arch, many oven builders, me included, like to separate the decorative outer arch from the inner parts of the oven, partly so it does not get so hot. If your tiles get so hot that the y fall of you just have to re-glue them.
Regarding the cracks on the dome, forget them. Most ovens have some cracks, it won' affect the performance and probably won't get worse. Most attempts to fix them are unsuccessful anyway.

[giol]

Re: Before pulling the trigger, in need of criticism

The good thing is that the summer is almost here so i have got a good 5 months of hi temperarures to help me in the process.I am just worried about all the water in contact with the iron table. I have painted the metal with rust resistant primer but too much water for too long is not easy to handle.

[giol]

Re: Before pulling the trigger, in need of criticism

Finished!!!
I want to thank every one here for their help and especially David S.