Perlite Pizza Oven

[daverook]

In a previous post, I was asked to report back on how my perlite pizza has gotten on with time! https://community.fornobravo.com/for...ney#post438811

I have attached several photos!

I built this oven about 6 months ago! It has been used about 12 times or so. I'm able to get it to about 400°C / 750°F (temperate measured near the fire and on ceiling) and the structure seems fine to me (it hasn't crumbled)

What I have noticed though, is the actual fire bricks that make up the base, do not really get that hot! I'm unsure why. They often do not get above 230°C/450°F which is a pain. This may be my bad technique as I believe the size of fire wood I was putting on was too big. I've now bought at axe and chopped to size, but as it's winter in UK, I do not want to use it in case it suddenly rains (and no idea if the cold rain could make a hot pizza oven crack)

Some of the negative things for me are: when I clean the oven out, if I accidently hit the inside of the oven with my scraping device, it takes a little perlite away with it - it is fragile despite being able to handle these heats

I do not really see my oven go "white" on the side when it's heating (as the tutorials show) - maybe it's the material, my technique or that I've not got it hot enough

Over all, I'm really happy with it; if I could do it again, I would go for a proper traditional build and not the perlite but - the difference in cost is huge! This pizza oven gives me a better taste than I get in an indoor conventional oven! I often freeze a batch (base and sauce only) and recook in oven at home for winter!

[UtahBeehiver]

What type and thickness of insulation do you have under the floor bricks? Low floor temps can be caused by two things, wet insulation or no insulation, if no insulation the floor bricks sit on thee concrete hearth which acts as a heat sink drawing down floor temps (not much can be done here other than recharging of the floor periodically while cooking) Wet insulation can be corrected by multiple fires but you need to find out where the water is getting in or the problem will just repeat itself. If you used a pcrete floor insulation and it was not dried out prior to floor placement there is a ton of water in the pcrete and will take a while to remove it via oven firings.

[Kvanbael]

400 C near the fire… is that with an active fire? My guess is that you are measuring the air temperature or a very superficial dome temperature. After you (re)move the fire, the reading might be a lot less.

[david s]

This table explains the story for your dome. Adding a lightweight aggregate to the mix like perlite reduces conductivity, strength and thermal mass, but increases insulation value.
Although you don't say what mix you used, as you've reported it is also subject to knocks and abrasions.

I suggest you keep cooking in your oven as long as it lasts, then rebuild it, reusing the floor bricks you have. Thanks for your valuable input.

[daverook]

UtahBeehiver

>What type and thickness of insulation do you have under the floor bricks? Low floor temps can be caused by two things, wet insulation or no insulation

I used Ceramic Fibre Board 1260 C-VITCAS Insulating Board HS:6806100000, Size1200 x 1000 x 50mm

[daverook]

And for the mix, I used 5 parts perlite, 2 parts white cement and 2 parts water

[david s]

Perlite is good for up to 1000C, the white cement (Portland) begins to fail north of 300C

[Gulf]

I’m not a fan of this type oven. But, IMO adding clay and lime would help future constructions of this type.