42" Pompeii Oven in Sidcup, UK

[Sidcup1]

Hi there, my name is Jim and here is my 42" Pompeii oven project in Sidcup near London, UK.

[Sidcup1]

Been 18 months so far. Problem is our weather....ahem !

[Sidcup1]

Made a brick saw by grounding out a larger slot on a small tile wet-saw, and fitting larger blade. Worked fine so far, completed the dome and wore out a ?10 blade.
Was so interested in using an indispensable tool, but as I promised the family pizzas from it for the World Cup 2014, I felt compelled to get a move on. So I built polystyrene form and cracked on. Also a brick saw that could cut deep cuts and angle each brick is quite pricey.

[Sidcup1]

I used a homebrew of 1:1:1:6 ....of lime, fire clay, Portland cement, and plasterers sand. Using a polystyrene form means you can't clean the interior or create neat mortar lines, so I tried to keep gaps between bricks as small as poss. This was straightforward on the first few courses but 2/3rds of the way up dome I began to reduce size of bricks by 1/3rd, and I started to diagonally cut one side of each brick so that it fitted snug to the one next. The last 1/4 of the dome, the top was laid with 1/4 bricks, as otherwise the gaps on the inner surface of oven would have been large.

[Sidcup1]

Put 1/4-1/2 of mortar all over dome them wrapped it up for 12 days in clingfilm. Afterwards it was that brilliant time when you rip up the polystyrene form and look inside.

[Sidcup1]

The teardrop effect was carefully avoided by correctly placing the entry arch in the dome. The walls of the dome ran smoothly into the arch, I was pleasantly surprised when I saw the pics. Got bits of polystyrene stuck in mortar in places, I'll get a brush on them !

[Sidcup1]

That's where I'm at ......so please comment, criticise and advise. Next is the entry arch and vent.

[gastagg]

Looking good Jim. Way to persevere! Are you putting a thermal break between the two arches? Check out kallipigous thread for a great thermal image showing the effectiveness of a thermal break in reducing heat loss.

[Sidcup1]

Thanks gastagg. Took a look at both yours and Kallipigous and was really impressed.
I looked into thermal breaks but I initially decided against them. I can't put a break in my floor as it extends under the dome arch continuously to where the entry arch will be built, and I have already built the dome arch. I could still put one between the vent and dome arch.
However, I am not 100% convinced of their effectiveness, despite the infrared pics. Basically, although the heat appears to 'stop' at the leading edge of the dome arch, does this necessarily mean it is being conserved ? It will be still radiating out heating the air, won't it ? It would, and indeed does as the pics show, stop the vent brickwork becoming hot, but does this necessarily mean the heat is being conserved for use ?
I may be wrong, but I imagine a more effective method would be to insulate somehow the outward face of the inner dome arch, but if you leave a small 3-5mm gap between the two structures, it's not really enough room for any effective insulation.
I may be wrong entirely. To sum up my point ..... just because heat isn't transferred from one brick to another doesn't mean that the heat is being conserved or insulated for use.
There were many interesting threads on thermal breaks....since the site has been revamped it's impossible to revisit these on the search function.
Any thermal engineers can chip in ?

[Gulf]

...............There were many interesting threads on thermal breaks....since the site has been revamped it's impossible to revisit these on the search function...................................

You can build your own search engine for the site through Google. Just pull up the google search page and do either of the following:

In this case, "thermal+heat+break" +"site:www.fornobravo.com. This is what I got for that search.

Also, the key words "thermal+heat+break" + http://www.fornobravo.com/community/. And, This is what I got for that search .

[Sidcup1]

Thanks Gulf, had played around with a google search but your method reveals more..... Amazing what you get from this site !!!!!

Reading further, a thermal break would allow the dome and arch to move independently to vent and entry arch. Having already built my dome arch on the landing floor of firebricks in a herringbone pattern, a thermal break is out there. Removing bricks under the arch would just create mega cracking I imagine. Just wonder if it's worth putting thermal breaks between entry arch and dome arch if the floor and both arches move as one ...with no break ?

[Gulf]

.................. Just wonder if it's worth putting thermal breaks between entry arch and dome arch if the floor and both arches move as one ...with no break ?

If your asking the question from the point of the gap being a "thermal break", I feel that you would still be getting the majority of the benefit of a heat break. If your asking the question from the point of the gap being an "expansion joint", I don't think that both arches sitting on the same floor brick is going to give you any problems. Neither, the springers of either arch nor the floor brick should be set in mortar. So, there should still be some movement allowed imo.