2024 Neapolitan oven build

[UtahBeehiver]

Nobody is going to look inside the top of the oven when it is 700F, they will be amazed how quickly and tasty the pizzas that come out are. Plus the dome is going to soot up every time you fire until it clears off (about 700F plus and there is also a unique smell when the carbon starts to burn off, kind of like an ozone smell).

[daidensacha]

I found vinegar and a wire brush moderately helpful for small amounts of relatively fresh mortar and very helpful for efflorescence. Mind you, I was using the homebrew Portland cement-based mortar, not the calcium aluminate-based stuff you have, so your mileage may vary there.

I was pretty disciplined when doing the dome, after each row I washed down and cleaned the bricks because I found out early the cement set like stone. What I have is some dirty water stains. I tested today with 50/50 vinegar water mix and it does the job, makes it easy to remove it with a wet rag. But to be honest, the inside of the dome is clean enough for me. The photos I posted the last days were deceiving, because the dark part inside the dome is where it was wet from me cleaning it. Today it had dried out more and the dark patch is not there.

As if its not already cramped fitting through the arch into the low dome, I sprayed some vinegar in there today and if I was going to do it I would need to wear a mask. I‘m not doing that.

[rsandler]

I found vinegar and a wire brush moderately helpful for small amounts of relatively fresh mortar and very helpful for efflorescence. Mind you, I was using the homebrew Portland cement-based mortar, not the calcium aluminate-based stuff you have, so your mileage may vary there.

[UtahBeehiver]

Vinegar and water mix is pretty benign and works best on efflorescence vs mortar. IMHO, give it a try, nothing to lose. I used muratic acid and water on the exterior of my oven to remove the efflorescence but it is definitely more aggressive and PPE is need.

[daidensacha]

Removed Indispensable Tool; refitted the center floor brick; fitted Schamott flue to vent.

It’s Sunday, there is a law in Germany against working on Sunday apparently, or so my wife always tells me. She was away this weekend so I forgot about that and reverted to my Australian conditioning.

I cleaned out the floor of the oven with a vaccum. Lots of dregs around the IT well in the middle of the floor which I didn‘t want to fall into the brick space when I removed it. Had my fingers crossed that the minimal sand I put in there when I levelled the floor was still in place, and if I could avoid stuff falling in when removing the IT, then the block should theoretically slip back in to place nice and level. The theory was good. The block dropped in with a flew little taps of the rubber hammer. Perfect level.

I chipped a little of the surplus cement spots away from the inside of the dome. Still needs a good clean, as my dirty rag left dirty water marks. I read someone used a vinegar and water mix to clean their oven. Does that really work? I have seen it used on external walls. Don‘t want to do any damage to the cement on the dome though.



I cemented the Schamott flue pipes on the vent, that was easy. Then I enjoyed the rest of the day off, apart from doing some calculations in sketchup on the chimney brickwork I want to start this week.

[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.

[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.

[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]

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]

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.

[daidensacha]

Ben Guillford’s Melbourne Firebrick Company that sells a brick kit just replaces the last 3 or so rows with castable refractory and it is fired in place.

That’s interesting. I understand why, as it’s fiddly as when the hole gets smaller. I thought as I got to the last courses it would get easier, but it’s the opposite. Requires more care and attention to detail.

Does the castable refractory require firing to set?

It raises a question I have about two different types of fire cement/ mortar available here in Germany.

1. Hydraulic binding mortar. Binding/ setting process is chemically triggered with addition of water. Has 30% clay,
2. Ceramic binding mortar. Binding is made through firing at temperatures of around 800C.

I’ve used hydraulic binding cement, and gotten used to it. The bricks need to be wet, and once cement added I need to put it exactly in place within seconds of contact as the water is sucked out as soon as two bricks are in contact.

Ceramic binding mortar was sent by mistake in my last order and I laid a course using it. It was totally different in consistency, a dream to work with. Stays creamy even after bricks are together, and allows for easy adjustments once they are. Can add brick wedges in gaps very easily. I removed the course and mortar as I wanted to complete the oven using the hydraulic setting mortar. I was unsure how, and if the ceramic binding mortar would set with temperatures reached in the oven.

Do you know if it’s possible to use ceramic setting mortar on an oven dome? It would make life much easier fitting the bricks.

[daidensacha]

I have two separate options both in process and I’ll choose the one I prefer when it’s clear to me.

I managed to cement the wedges from option 1 above together and it’s drying inside overnight. I’ll cut down and cement a keystone in it. I figure in one piece it will be stronger. I’ll leave enough keystone sticking out the top to use as a handle so I can hold to drop it into the hole when fitting. Can cut that off after cementing it in. It’s very close to the hole size but will need some minor fitting adjustments.



I’ll also start cutting down my option two using the wet cutting saw to get my side cuts of the stone. Hopefully that will mean less grinding and the bricks will hold together.

[david s]

Ben Guillford’s Melbourne Firebrick Company that sells a brick kit just replaces the last 3 or so rows with castable refractory and it is fired in place.

[nlinva]

Your brickwork is amazing, and to a far greater precision than mine. For me, this meant that your option 1 was basically out of the question, so I went with your option 2, and it worked nicely for me.

I do have one caveat: in my case, the cemented-together keystone bricks did not hold together in the course of using the angle grinder to get the correct shape for the keystone. I had to do a fair bit of grinding, and when I was almost done, the two bricks came apart. This was not a big deal: I simply scraped away the mortar, cleaned the surfaces, and re-cemented them together, making sure to keep them oriented correctly relative to each other and to use the same thickness joint. But just something to be aware of that it might happen.

Also, while it is true that you'll never see the outside top again and rarely see the inside top (unless you make a real effort, you can of course take lots of pictures to remind yourself how good it looks underneath all the insulation that's going to come on top of it!

[daidensacha]

At least from the outside, that looks like very neat work on those last courses, especially with having to dispense with the IT. Nicely done!

I would just make a 2-brick keystone; on my first oven I actually made a 3-brick sandwich. Up to you of course, and if you enjoy the work enough to make half-height bricks to bevel, certainly go for it. Even you will rarely see, much less stare at, the top of the dome, and certainly no one else will. So, do whatever satisfies you at the moment.

It’s a good point that no one will see it. It’s so true. I tried looking in from the front today, and short of crawling in, it’s really hard to see the top of the dome. Appreciate that feedback.

I hedged my bets and decided to do both, and see what works best.

Option 1. I cut the half height bricks, and then the wedges first up. It’s really hard to work in the small hole. I tried various ways to support the small wedges, but it became to finely so I removed them. I started cementing them together, and sixteen wedges are now 6 pieces drying. I tied strings around the wedges to see how how the come together, and it makes a slightly bigger piece than the hole in the top of the oven. That’s ok, because tomorrow I’ll put the six pieces together, then cut a keystone and fit it in the middle of the cemented wedges. I can then cut down the single piece to fit in the top of the oven, Maybe not the conventional way to go about it, but if it comes together it will look nice at least.

Option 2. I cemented 2 bricks together, and they are drying in the garage. I cut templates for the top and bottom of the hole, and will transfer those shapes to the top and bottom of the 2 bricks. Then I’ll cut it down to fit in the hole, and see how it looks. It’s a backup in case my wedges become to complicated, and may well become my first option if it looks ok.

I’m resisting the urge to rush, given the work its take to get to this point. I know in a few days I’ll be fitting the keystone, and will then be onto the vent and chimney.