27inch/70cm Pizzo oven build in Rotterdam/The Netherlands

[Phartog]

Hi Builders, I made some progress again!

I realized when trying to build the bricks over the arch, that my arch stones were not long enough right on top of the arch. I could have proceeded, but I decided I had to reconstruct part of the arch, to have a better support in that area. So I had to go backwards a bit. I broke down part of the arch and made effort to cut some new arch stones. After that I could proceed with the next courses. And now I managed to close up the whole dome.

Next up is starting on the flue gallery. I already 3d printed a mold to cast the plug (probably cast it from a mix of plaster and vermiculite, or some other breakaway plaster mixture). I build a gallery entry template, and everything comes together. I do have some thinking headache on how to proceed. I have a flue pipe lying around of 120mm, but I actually should have a pipe of 125mm (I know the difference is small). But I am also considering going for a twin walled flue pipe, that makes the whole construction proces more complicated).

[Phartog]

I made some good progress. For the preparation of the flue gallery I first prepared a new wood template with the necessary offset . Then I started with the first layers of bricks for the flue gallery. Next I casted the mold plug for the flue gallery transition. I did some tests with the vermiculite - plaster mixture, because I have the small grain vermiculite, I noticed I had to add a lot of water to get a workable mixture, so I eventually decided on using a bit less vermiculite, so I think I went with a 1:5 ratio (plaster - vermiculite) and just added water until it was the right consistency.

Eventually it was easy to work with, to get the mixture to even out in the plastic mold I even used a vibrating needle (normally used for concrete) to get some of the air out. I was happy with the result after removing the plastic parts. Some of the big air gaps I filled up with plaster. Because I used vaseline in the plastic mould, the wet newspaper didn't stick to the plug, so eventually I thought, let's just layer the plug with some more vaseline to prevent the plug to adhese to much to the cast.

I made some templates to cast the homebrew-castable (I used a mixture of the homebrew with the addition of ss needles, AR glass fibres and PP fibres). I started out with a batch that I thought would be enough, and mixed all the additions (fibres) in there, but the amount was not enough at all and I used up all of my SS needles (I made them by cutting up a SS twisted wire). So the next batch I just used some more AR fibres.

The cast looks pretty good, because I used less vermiculite for the mold plug it was a bit of a struggle to get the plug out, but eventually it work out. I had to even out the top of the cast a bit, to make sure the flue pipe would be level.

I put some more blankets on the dome, I already did one level of 25mm, now I have another layer of 25 mm.

Next I want to finish the flue gallery with the decorative arch in front. Just a question for david s . I think you have the decorative arch isolated from the rest of the flue gallery, you make some gap in between the the flue gallery and the decorative arch? Do you think this is mandatory/needed? The cast I made became a bit thicker then I would have liked, so the decorative arch would get very thin, so I think it needs some of the strength of being mortared to the cast.

[david s]

What an excellent result. The form of your casting will produce an efficient exit for flue gases and smoke. The relative thickness of your cast compared to brick units results in far less of a heat sink effect drawing heat from the dome which will make the oven more efficient, with a casting free of vulnerable mortar joints, and the shallow gallery will mean excellent access to the oven chamber making working the oven a delight.
it doesn’t look like you have enough room for a separate decorative arch. It might be easier to complete the brick arch in front of the casting with some thinner slices, or better, cast a decorative piece in a single section.
The idea of providing an expansion gap is to allow thermal expansion to occur inside the cooler outer rendered shell and outer arch.

[Phartog]

What an excellent result. The form of your casting will produce an efficient exit for flue gases and smoke. The relative thickness of your cast compared to brick units results in far less of a heat sink effect drawing heat from the dome which will make the oven more efficient, with a casting free of vulnerable mortar joints, and the shallow gallery will mean excellent access to the oven chamber making working the oven a delight.
it doesn’t look like you have enough room for a separate decorative arch. It might be easier to complete the brick arch in front of the casting with some thinner slices, or better, cast a decorative piece in a single section.
The idea of providing an expansion gap is to allow thermal expansion to occur inside the cooler outer rendered shell and outer arch.

Thanks for the reply David, my plan is then to finish the brick arch in front the casting. My plan is to make a custom decorative arch from ceramics (glazed stoneware of porcelain) as I am a ceramist and I can or create small decorative tiles or one full decorative arch. I can make them relatively thin (maybe 1cm thick) and mortar them to the front, I can even make a bigger rectangular part to cover the cal sil board in the bottom.