Planning my 32" cast oven

[AndreasP]

Finally, the pizza oven is done. Thanks a lot to everybody who helped me realize this oven! It's been a fun journey.

To finish the oven I

• Painted the stucco with Red Guard to add a waterproofing membrane to the oven.
• Tiled with penny round tiles

The tiling was a lot of effort. Had to cut the sheets in strips one tile wide so that I could try and follow the round dome shape.

I may still paint the chimney black, but that won't take long.

Another pizza party tomorrow.

[AndreasP]

Made some progress last weekend.
Covered the oven with the scratch and brown coat.
Covered the whole thing with plastic to let it cure slowly.

I will wait for a week before painting it with RedGuard. Once that is dry I will add the tiles.

Hopefully the breather hole at the top and the V-crete being uncovered around the chimney with flashing on top will be enough to keep the tiles / stucco / oven from cracking should any water get into it.

[AndreasP]

My design also employs the same design feature. It allows the inner parts of the oven to expand and contract freely inside the cooler outer shell and decorative arch. I have tried a number of solutions and like you l fill the gap with blanket and seal it off at the top with some vermicrete around 6 mm thick. I make it a bit richer (5:1) and run a pointing tool over it to compress it into the space. Obviously there are some bonding issues and the gap will fill with ash anyhow. You don’t want it to be too strong because you are asking it to act as an expansion joint, so it can’t be too strong. I’ve tried high temp silicon, but it’s not durable enough in that position. Other refractory caulks also failed which just go hard but not flexible. A floatingstainless cover over the gap is another solution that I’ve not pursued. I don’t bother filling the gap on the sides or at the top but just rely on the air gap which prevents conduction heat travel.
Let us know what you’ve come up with.

David, for now I decided to leave it as is. Last time I made pizza I had no issue with V-crete falling onto the pizza. I was worried about that form my attempt to fill the top and side gaps.

[AndreasP]

Thinking of changing my approach to the final render. Instead of finishing it with stucco I am thinking of tiling the dome in the hopes of getting a more waterproof finish.

I have looked around on the boards here and am wondering:

1. It seems that most people add a scratch and brown coat of stucco, then tile on top of that with an acrylic adhesive
   • How thick would you make these layers. I don't have a lot of space around the back of the dome and the thinner the better
   • I would plan to use a tile adhesive used for shower tiles
2. Any suggestions for the grout? Again, I would use what is used for showers
3. I am thinking of using a waterproof paintable membrane below the tiles. I know the challenge of keeping water in, but I have a vent hole at the top and around the chimney pipe
   • Where would this membrane go? I am thinking that on top of the brown coat (right below the tiles) seems to make the most sense, any suggestions?

Any feedback would be appreciated.

[david s]

My design also employs the same design feature. It allows the inner parts of the oven to expand and contract freely inside the cooler outer shell and decorative arch. I have tried a number of solutions and like you l fill the gap with blanket and seal it off at the top with some vermicrete around 6 mm thick. I make it a bit richer (5:1) and run a pointing tool over it to compress it into the space. Obviously there are some bonding issues and the gap will fill with ash anyhow. You don’t want it to be too strong because you are asking it to act as an expansion joint, so it can’t be too strong. I’ve tried high temp silicon, but it’s not durable enough in that position. Other refractory caulks also failed which just go hard but not flexible. A floatingstainless cover over the gap is another solution that I’ve not pursued. I don’t bother filling the gap on the sides or at the top but just rely on the air gap which prevents conduction heat travel.
Let us know what you’ve come up with.

[AndreasP]

Made a bit more progress last weekend. I was able to attach the cast entrance
I tied it off with the wires I had cast into it and filled the gap with 10:1 Vcrete.
Unfortunately it is not bonding well with the cured concrete (kind of expected)

I am planning on redoing it as follows:

• stuff gap approx. 1/2" - 3/4" with fiber blanket
• cover fiber blanket and gap with Rutland Fireplace mortar, works up to 2000F, plenty for the entrance dome.

I am wondering, will the above approach work?
Will the mortar bond to the cured concrete surfaces (both the gallery and cast entrance)?
Instead of buying the Fireplace mortar, should I just mix up a bit more Homebrew and use that?

Any suggestions?

[david s]

Yes I make them myself using a press moulding technique and firing them to 1150C in the Intergalactic Explorer see here.

https://community.fornobravo.com/for...kiln#post14564

The top collar is sealed to the stainless pipe with high temp silicone.

[AndreasP]

David,
Thanks so much, that was what I remembered seeing.

I assume you fabricate the terracotta parts yourself?
Does the upper terracotta collar sit right up against the vent pipe or are you also using high temp silicone for that part? I assume silicone?

Thanks again for your help.

[david s]

I use a similar system so moisture in the insulating layers can find its way around the flue pipe. The attached pic tells the story. The moisture finds its way out between the two terra cotta collars, the lower one having a larger inner diameter than the top one. I seal the top collar to the pipe with high temp silicone.

Be careful of rendering directly against the pipe or its expansion will crack the render (seen lots of that). if you wrap the pipe with some cardboard around 5mm thick, render up to it, then remove it when the render has set, the space can be filled with high temperature silicone, provided it is high enough not to be affected by flame up the pipe.

[AndreasP]

Question on the stucco around the chimney

I am thinking of only putting stucco on the vertical walls around the chimney, leaving the top (right around the pipe) uncovered. Then sliding the collar down and sealing the collar around the pipe.
This way any moisture that finds it way through the stucco (I will use a sealer on top of the stucco) has another path to escape (other than the center breather vent).
I am a bit worried about being able to seal the flashing to the chimney. I only have a double walled, uninsulated chimney, and especially when I start the fire and the flames are big, it get quite hot.

Any thoughts? I think I have seen something similar in one of David's responses or threads, but I can't find it anymore.

[AndreasP]

Made a little progress on finishing the oven today. I was able to build the form for the front arch.

I also put some flashing around the bottom of the oven and sealed the bottom with high temp silicone (even though it won't get hot there).
Screwed the flashing and galvanized mesh into the foamglass. It really only needs to hold it in place until the stucco is covering it.
The hope is that this will give the oven another layer of waterproofing when I pour a countertop around it. The flashing will be higher than the top of the countertop, so even if there is a gap between the countertop and the stucco I hope to have a good chance to keep the floor insulation dry.

I will have to wait a few days before I stucco the oven, we have rain forecast for next week.

[MarkJerling]

I usually do max. 2kg flour per batch so that gives me around 3.3kg per batch (with water, yeast, salt) which fits one of my dough boxes perfectly once risen out. I prefer keeping the batches separate rather than combining it further into an even bigger dough ball! Most I've done so far is 2x 3.3kg batches (so 28 pizzas at 235g per pizza) but this time will be more! Another problem is fridge space. Logistics logistics!!!

Thanks! I can do with the luck with the weather. Normally, December is dryer but so far it's been a very wet spring / early summer.

[AndreasP]

Mark,
that sounds awesome. How much dough do you make at any one time? If it gets too big I think it's hard to handle.

We are going to have another smaller party, 12 pizzas or so tomorrow. Should be dry here.
Good luck with the weather!

[MarkJerling]

We're planning our biggest pizza party yet for Tuesday night. Maybe around 50 people so that will be the most dough and pizzas yet!
Wish me luck. I've been hoping for dry weather. We've had 166mm of rain already this last month.

[AndreasP]

Right, bread machine only makes 1kg, 7 pizzas. But I can just run it twice the evening before. If I were to do more than two portions I am sure I would knead it by hand.
Yes, I used the Caputo 00 flour, the taste was noticeably better than the Trader Joe's dough.