2024 Neapolitan oven build

[daidensacha]

Jobs for the week

I had my first day off today since I can‘t remember . I covered the oven with tarps last night as the render over the concrete brickwork was drying much slower than that over the old recycled clay bricks. This morning its stiffened up nicely, as it stayed reasonably a warm 12C overnight.

My main task this week is to insulate the dome with ceramic fibre blanket and the first layer of V-P-Crete. I‘ve listed a bunch of other tasks to do when I have spare time.

1. Cover dome with 100mm of ceramic fibre blanket.
2. Fill chimney and sides of arch with Perlite.
3. Mix and cover dome with 35mm of homebrew V-P-Crete.
4. Oak doors: Need to refit one hinge so the doors fit squarely together when closed. Have a little repair work to do on the render around a few hinges.
5. Tile under granite landing.
6. Add final layer of render over the chimney and arch frontage.
7. FIt gutter and downpipe for terrace roof (sheets hopefully delivered end of next week)
8. Fit light on front of oven above arch when render is dry enough.
9. Fit light switch, and connect wires to light and mains. (not connecting into the mains until I have the roof on)

I‘m excited that I begin to see a light at the end of the construction phase. So happy that I cut my last bricks as my hands showing signs of the work they have done. I applied for a new passport a week ago, and had no fingerprints left, haha. I explained I have been building a pizza oven and that the stones are like sandpaper. What to do….

My todo‘s:

1. Measure and order granite for the work benchtop once the oven is rendered and I can be sure of the exact measurements.
2. Source a nice slice of an oak tree truck for the bar at the back of the work benchtop.
3. Order double walled stainless steel flue for extending the flue up through the roof.
4. Add crown on the chimney once the flue extension is done.

[nlinva]

Yes, I have the same fingerprint issue. My computer, which I can normally wake up from sleep with my finger, no longer recognizes it. :-)

[david s]

Toiletman Thanks for your spreadsheet examples. Given you showed one for Perlite and one for Ceramic Fibre Blanket, it would be interesting to see how Vermiculite compares. I have all, and can fill the remaining space with any of them. Bits trickier to get the ceramic fibre in now though, so dry Perlite or Vermiculite would be my choice at this stage. Building the oven has introduced me to things I never considered before. Heat movement for example, as explained very clearly by david s early on when explaining the function of the heat break. Heat loss through convection and conduction are to be considered.

A double walled stainless steel flue has 30mm of insulation in it, so my reasoning without going into it scientifically like you, was that 35mm (1.5“) would be sufficient around the flue. The reason I want to fill the remaining void is to prevent/limit the walls heating. Hence I wanted to fill the void to prevent the transfer of heat via convection though the air. I thought that would be more than conduction through dry Perlite filling the empty space.

A question arose reading your chart, where your top end temperature range is 300C. Is that a realistic possibility, that the flue gets that hot? I thought it would be less, given its not exposed to the direct fire, only the. exiting smoke.

Putting a light was in my plans, and I had only considered running the cable up the flue and then through the wall. Heat being the major problem, and not knowing exactly how hot it would get. As I planned on rendering the outside of the chimney I decided to put the cable conduit in the wall from outside. Yes its ugly, 100%. But it wont be seen. It’s been a good process, learning lots, and I would do some things slightly differently with wisdom of experience. Like for example, my lintel. I would make my one that follows the shape of the dome next time, to an extent, to allow for good clearance. I would also set the rear all another brick width back, to allow for more space inside the chimney at the front and back of the flue. What I have is functional, but it can be improved.

I see your in Holland. Similar weather to here a bit I guess. I became used to working through rain now, with a tarp over my oven.

Regarding the perlite vs air comparison, as well as the perlite eliminating air flow in the space, it also introduces a barrier for radiant heat. On pondering this I remembered a technique used in double glazing of windows where the space could be filled with loose insulation (I think it was polystyrene beads which were pumped into the space when required, or pumped out if views were preferred.
Regarding K values, they are the reciprocal of R values. There are many different units used for insulation value, which makes things confusing. Time is also an important factor, sometimes not included.
Thinking about your problem last night when I was firing one of my ovens, one with a double flue (5”/6”), the outer pipe after one hour of firing, I could hold my hand against the outer pipe for about 2 secs. After 2 hrs only 1 sec.

[daidensacha]

Oven Insulation Started

I guess to much is better than not enough. When I ordered everything for my oven back before spring, I did some calculations and ordered 3 x 7.4m x 610mm x 25mm rolls of ceramic fibre blanket. Then I saw an offer a month ago and ordered 1 x 14m x 610mm x 13mm roll to use in the vent and chimney. I had about half the roll left when I finished insulating around the vent and flue in the chimney, and I filled the chimney from the arch up to over the vent.

So yesterday I got stuck into covering the dome with ceramic fibre blanket. After covering the dome with 4 layers, I had lots left over. So I added another 2 layers on top of the dome. It now has 100mm around the sides, and 150mm on the top, with about 200mm over dome where it meets the chimney. It wasn‘t planned to have so much, and maybe it’s overkill, but better than having it sitting in my garage and not using it. I covered it with a layer of chook wire, with screws into the calcium silicate under the dome to hold the wire.

In the afternoon I refitted one of the hinges for the doors, and they now fit flush with the door jam under also fitting. I need to patch some of the render around the hinges, and the door jam, but I‘ll do that when adding the final layer of render on the chimney.

Today I started on the first layer of homebrew v-p-crete.

Recipe: (parts

1. 5 parts Vermiculite
2. 5 parts Perlite
3. 1 part cement
4. 1 generous handful of clay powder per 1 liter of cement
5. Water to mix by hand into the right consistency.

I‘m no expert and my experience with this recipe is limited. The clay powder seems to make it easier to work with, besides making the mix a nice brown color. Theres a knack to adding it, and I got that pretty quick. Scoop up enough to fill both hands, then plonk it in place against the dome with one hand holding it against the dome, and the other patting it down flat on top. Adding horizontal layers one at a time until it curves over and on top of the dome. Then I poured a bucket load on top, spread it out, and patted it down to around 35mm thick. Possibly a little more in places. When finished, I scraped back the high points, and filled the low points to get s somewhat even shape over the dome. I put a vent in the top as well. A hydraulic vent (as described in the Forno Bravo forum) screwed into water pipe. It sits on the ceramic fibre blanket, and will give me peace of mind knowing if there is for whatever reason a buildup of pressure in between the dome and outer render then it has a release.

Now the wait for it to dry so I can do the next layer.


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[david s]

With so much insulation blanket the insulation value of your p/v crete doesn’t matter much, so it’s primary function is just to restore an even shape and surface for a final render/stucco. Once it has set and dried a bit (usually around 24 hrs you can carve back any high spots and fill any low spots with the same mix. After covering the whole thing, simply tapping the surface with a trowel produces a very good surface to provide a suitable substrate for the render coat (after drying and drying fires).

[daidensacha]

With so much insulation blanket the insulation value of your p/v crete doesn’t matter much, so it’s primary function is just to restore an even shape and surface for a final render/stucco. Once it has set and dried a bit (usually around 24 hrs you can carve back any high spots and fill any low spots with the same mix. After covering the whole thing, simply tapping the surface with a trowel produces a very good surface to provide a suitable substrate for the render coat (after drying and drying fires).

That’s good to know. My next coat will primarily be to make the sides flush with the stand, and to form a good shape with nice curves. Looking forward to it.

Looking like I’ll have about 400 litres of Perlite and vermiculite for the garden. It’ll be really good for my vege garden.

Also looking forward to the drying fires, but I’ll sort my terrace roof and flue first.