2024 Neapolitan oven build

[daidensacha]

Castable refractory uses calcium aluminate cement as the active cementious ingredien. Its fast setting and curing and refractory nature make it a suitable material. Using a conservative firing schedule up to service temperature, with the addition of burnout fibres, prevents steam spalling. The material only begin to vitrify above 600C, converting the chemical bond of the cementious proportion to a truly sintered body. This same material is used fore commercially cast ovens.

The other product you are referring to I think is a sodium silicate based one. Check the data sheet on the product for details.

Yes, silicon oxide based. SiO2

I wonder if it’s possible to trigger the binding process at temps less than 800C? In the information it states “around 800C”.

Thanks for the info David. When my ovens finished I’ll do and experiment and bake a few bricks at around 600C to see how the binding is after.

[david s]

“I wonder if it’s possible to trigger the binding process at temps less than 800C?”
Sintering begins at 573C when the body becomes permanent due to temperature. As the temperature gets higher the body becomes harder and stronger. Stoneware (1200-1300 C) much harder than earthenware (600-1200 C), porcelain (1300C+) harder than stoneware. Unfortunately the 500-650C range can be quite damaging because different materials have different expansion rates which leads to damage unless ramped up slowly and controlled. This is something not possible with a wood fired oven because of the chamber design and the fuel used, so it’s highly likely to result in damage if attempted. The castable refractory proves quite adequate for WFO service temperatures.
Additionally if sand is used as the mortar’s aggregate rather than crushed fired clay (grog), it has a tendency to turn to glass at higher temperatures, particularly in the presence of fluxes.

[daidensacha]

Custom Keystone Sun

My ring of wedges set nicely overnight, so after watching the AFL (Australian Football League) grand final, I made the most of no rain and cut the bricks I cemented together to get myself a piece of brick to make the keystone insert for the wedge ring.

I marked the top and bottom of the cemented brick from the templates I made overnight to match the top and bottom of the hole.

Another perfect use for mr Chipsters jig. Set the angle for the side cuts, then in 5 minutes the piece was ready. I made a few small adjustments with the 125mm grinder, and it fitted really well.

I took the wedge ring to test the fit in the top of the oven dome, and it needed some brick removed from the outside. I used the wet cutting saw to make cut the majority, then used the grinder to take out the rest. The ring held together.

I cemented the keystone into the wedge ring, leaving a small handle on top to make it easier to drop into the oven dome hole. It turned out like a sun, with the wedge pieces around the circle, I’m sufficiently happy with it that I decided not to cut the keystone from my above listed option 2. Will fit it in a few hours, weather permitting.

I know many build the Tuscan style dome. My recommendation, if you have any claustrophobic tendencies, then it would be preferable over the Neapolitan style dome. I set up a plank from the front of my ladder to the oven opening, laid on my back, then crept backwards with one arm over my head so i could fit in. I’m not claustrophobic and it had me on edge. I wanted to check the inside of the dome, and fill any small gaps with cement while there is still light from the small hole in the top of the dome. I got used to it after bing in there a little while, but it’s definitely not fun.

Some pics of the evolution of the custom keystone.

[daidensacha]

Keystone in and dome done; Vent fitted

Keystone in.
After letting the keystone set for a few hours, I crawled down the plank on my back into the oven dome. Really not fun! Our son and a friend of his helped by inserting the keystone and fitting it. I got shoulder cramp half way through, unable to easily get out, and without space to stretch, it was really a test of my endurance of pain. I breathed through and got the keystone in, although 1mm lower on one side, acceptable for me. I left the handle on top of the keystone, not that I will use it now, but it was handy to hold on to, to fit it. I might just see if I can’t repurpose it into a decorative flower, that no one will ever see when it buried under the insulation. But I will know it is there. I have a little bit of cement stuck in the inside of the roof, which is annoying me, So I might venture in once more with a chisel to chip it out, so it looks nice.



Fitted the vent cast.
I’m so happy the dome is finally done. I moved to thinking about starting the chimney, and asked my son’s friend for help to fit the vent cast I made. I would like to give credit to david s . It was his generous sharing of knowledge and experience, and support that inspired me to cast the vent in refractory concrete. The arch vent is rectangular, and transitions through the refractory concrete vent to 200mm diameter circular vent at the top on which I have mounted a schamotte adapter plate for 2 x 200mm schamott flue pipes. The transition from the rectangular vent in the arch to the circular vent to accomodate the 200mm flue is the same area so it doesn’t impede the smoke flow up the flue. Also curved walls in the refractory concrete vent so to allow smooth flow upwards.

It sounds a lot, but with Davids input I made it happen as the last think I want is smoke flowing out the front of the arch. I was admiring it once it was fitted. Thank you David. I’m so glad you gave me the tip and support by patiently answering my many questions.