42" low dome build in Holland

[atak]

Hello, I am building a neapolitan oven. It is my second one.
I have poured the foundation and put sand-linestone walls on it.
Tomorrow I will get 3 slate's front 2x1 meter and 12 cm thick.
We have a mini shovel and use it to place the slat's.

[atak]

They brought the slate's they were only 40€ each. I have got them on the walls and can start with the oven build.
Unfortunately my avatar is wrong, the puppy I hold has died yesterday, 12 years old and always in our thoughts.

[atak]

A question, why is the door entrance always round and not square?

[rsandler]

You can have a rectangular opening if you want--the Pompeii oven plans actually suggest this as the default way to build the oven opening, using angle iron to support the span. A round door means you're building an arch, which is more-or-less self-supporting. A square top oven opening would need some kind of support to hold up the span. I think most builders on here find the angle-iron support feels crude, and prefer to at least have a partial arch, so you'll only see square doors on very old posts. YMMV. Possibly there could also be cracking issues with expansion and contraction of the angle-iron (metal and brick expanding at different rates), but I assume there's some way to engineer that safely.

[SableSprings]

I went with the rectangular opening for my oven and used a piece of angle iron across the top. To allow for expansion/contraction during use, I did not cement my bricks to the metal, just laid them on. I also left a gap on both ends to allow the metal to expand laterally during firing. Having a rectangle opening made it east to fabricate my baking & firing doors. I also have appreciated the larger access to work the oven's bake (+12 baguettes, fire movement during pizza, etc.). Since being built in 2009, nobody has ever said "It would've looked better with a curved entry"

[atak]

Thank you for the answers, I will make a square one, I can weld so no problem.
Another one, I have for 12 years 100 isolation stones lying here and want to use them.
What is better, first fireclay than isolation stones and than the pizzafloor or first isolation stones than fireclay and than pizzafloor.

[UtahBeehiver]

Clay is really only needed as a leveling medium in either case, isolation bricks or oven floor bricks. The hearth looks really flat and the isolation bricks look like they are laying very flat.

[atak]

That is right, it is all very flat. They are laying loose on the floor, must I glue the outside one's or just go on laying the floor.

[rsandler]

You can lay the insulation directly on the hearth slab and the cooking floor directly on the insulation, no adhesive or mortar needed. The weight of the oven will hold it all down.

[atak]

I have decided to lower the opening to 9 inch because the metal angle iron wil be at the same hight as the opening. We will not do big roasts in it. will it breath enough to keep the fire going?


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[david s]

The oven opening needs to be big enough for decent access to work the oven. In this regard the larger the better. The drawback is that the larger the opening area, the greater the heat loss. Regarding the height, it needs to be tall enough for the largest roast or bread loaf you want to cook. Width is more important regarding access for pizza and wood loading and arched or semi circular tops apart from being far more structurally stable than a rectangle, can provide more height without increasing the area as much. A compromise between access and heat loss has to be arrived at.

[atak]

I also have a plasmacutter, so if I need more hight I can always cut some metal from the horizontal beam. The inside angled iron [ 2 inch ] will be welded agains the inside of it so no structural problem I suppose. Still waiting for my order of bricks aso, they are in backorder.

[david s]

Generally WFO’s are built with masonry only and the stability of the hemisphere which requires no buttressing or bracing. Introducing steel into the build can provide strength if required but comes with it some problems.

One of the problems with steel against masonry in high heat situations is the much higher thermal conductivity of steel compared to masonry. On heat up the steel expands more than the masonry that surrounds it, which can result in cracking of the masonry as the steel expands against it. Sometimes it’s possible for allowance for expansion to be made to reduce this stress.Conversely on cooling down the steel's conductivity leads to it cooling faster and contracting against the hotter expanded masonry, shrinking hard against it. Some pottery kilns have steel bracing with threaded rods and nuts which can be adjusted in tune with this expansion and contraction problem. Although kilns operate at more than double an oven's service temperatures, the pronciples still apply. I have seen ovens with steel door frames that have severely cracked the outer shel that surrounds them.

The second problem is of course corrosion of the steel.
Unfortunately heat accelerates reactions and rust can become a problem. Never use galvanized in a high heat environment as it will produce highly toxic fumes around 400C.

https://pmc.ncbi.nlm.nih.gov/articles/PMC2796768/

[atak]

You are right, I will clean the iron from the sink coating. When you weld sink you get these white feathers floating in the air. I take the risk of a crack around the door, there must be a vertical hold for the metal band around the soldiers. I thought all or most neapolitan ovens have a metal band on the soldiers to take the forces from the low dome.

[atak]

Yes, my bricks aso are in. Layed the floor and the soldiers so I can bend the support for the first ring. Went OK.
Tomorrow I will try to place the soldiers and than let it harden for one day and then place the ring on it and weld it together.