PNW Pizza

[Lotus19]

Thanks, David. How can I strengthen my vermiculite base? Parts of the bottom edge are still crumbly and it's a bit worrisome. Can I make a stronger mix of the vermicrete, say 3:1, and just skim the outside to firm up the crumbly bits?

[david s]

Yes, of course, but probably easier to use a sand/cement 3:1 mix.

[Lotus19]

Thanks, will do!

[Lotus19]

Worked on my gallery form this weekend, but did not have time to do the cast.

Meanwhile, I got a 6" x 36" double-walled SS chimney and realized it's VERY heavy. I was planning to use David's tab method (rather than using an anchor plate), but I'm worried about the little tabs supporting the weight. I realize they'll be more additional vermicrete and a stucco layer to help support the weight, but still concerned... I'm thinking of drilling three or four SS screws into the base of the chimney and having them stick out an inch or so. These would rest on the top of the hole in the cast and support the weight, rather than the thin tabs. I'm sure it will work, but it is a bad idea?

Thanks,


Joe

[david s]

I’ve never had a problem with the seating of the pipe with my tab system and some are pretty tall at 2.5m (3 sections of pipe). My pipes are not heavy, but maybe yours are thicker. Mine are made of 0.55mm 304 stainless. Because screws are likely to come loose at the threads from thermal expansion cycling I think you’d be better to either make the tabs a little wider or just cut more of them, say 6 rather than 3

[Lotus19]

Got the gallery cast this weekend. Went fine but I think I made my chimney form a bit too big. I think I was worried about some of the posts I have read about the chimney expansion causing cracking in the casting.

Did a test fit the next day with the actual chimney and there's probably 1/4" gap around the whole pipe. Sorry, didn't get any good pics.

What's the best method to fill? Vermicrete or stuff with fire blanket?

[david s]

Got the gallery cast this weekend. Went fine but I think I made my chimney form a bit too big. I think I was worried about some of the posts I have read about the chimney expansion causing cracking in the casting.

Did a test fit the next day with the actual chimney and there's probably 1/4" gap around the whole pipe. Sorry, didn't get any good pics.

What's the best method to fill? Vermicrete or stuff with fire blanket?

That will be ok. You could expect an expansion of the pipe to about 3mm extra in diameter.
If you use my method of pipe attachment, then no anchor plate or drilling is required. You could stuff some blanket in the gap, but I prefer some 5:1 vermicrete to seat the pipe in position. If you build the vermicrete up around 150mm higher than the top of the flue gallery it will support the base of the pipe really well. The render can then surround the pipe (do the cardboard trick again, remove it when the render sets then fill the space with high temp silicone. This prevents the expanding pipe from cracking the render as well as preventing water entry at that point. If it's high enough away from the fire the high temp silicone copes ok.


Instead of using two terracotta caps as I do to allow the over dome insulation to vent to the atmosphere you could drill some holes in the base of the pipe, as illustrated, so water vapour in the insulation layers can escape to the vent pipe.(I've not tried this but can't see why it wouldn't work. It seems to me to be a far more elegant solution than an exposed vent.

[Lotus19]

Just finished filling the space around the chimney with some 5:1 vermicrete. I wrapped some thin cardboard around the chimney. How long before the vermicrete sets and I can remove the chimney/cardboard?

[david s]

It depends a bit on your weather (temperature), but 24 hrs should be ok. The vermicrete is ok to be hard up against the pipe as there is some elasticity in it and you want it to support the pipe. The cardboard is only meant to keep the more brittle render away from the pipe. The drying fires should be done before applying the render. When doing the cardboard trick I cover it with some plastic or oil it to prevent the render sticking to it. This makes removal easier.

[Lotus19]

Got the blanket and chicken wire on last weekend. Have had a couple of warming fires with some briquettes, but they really don't give off too much heat. Been using the propane burner of my turkey fryer on low and seems to be working well...

Today I applied the vermicrete render, using the 10:1 mix, although I did half perlite, half vermiculite. I did throw in some clay, but it's still pretty tricky to work with. Took my time and was able to get it done. Celebrated with a Guinness!

Will let the sun and breeze dry it for a week, then get back to my curing fires.

[david s]

Nice job. I can see it still looks moist. It will turn white in a day or two, but you can be sure it will still be moist deeper in. Be careful of using the turkey fryer as the flexible hose may have a tendency to cook. Having no flame failure device on it runs the risk of filling a hot chamber with unburnt gas.

[Lotus19]

Hey guys! Just wanted some opinions on what to do about the facade of my oven. I guess I didn't plan too well with my footprint, as the front of my oven is about 3/4" from the edge of the hearth slab. I know most of the facades that people cast are around 2" thick, so I think if I went that route it would hang over too much. I also didn't place any wires into my cast, so the only anchor would be mortar holding it in place.

I'm thinking about using some thin stone siding, tile or thin brick flats around the face of the arch. Should I trim back the exposed insulation blanket and apply some vermicrete over it, or use something else? I'd like to affix the tile/brick first, so that when I do the stucco I can get it flush with the outer edges. Or do I need to do the stucco first, then apply some thinset over the arch and apply the tiles/stone?

Also, can my decorative piece cover the firebrick, or can I only go as high as the base under the oven (see my photo examples)? Most of the cast pieces I've seen cover the front of the firebrick, but I'm just not sure how they're attached.

Can you tell I'm not really well versed in cement/mortar/tile work?

Thanks,

Joe

[david s]

The problem is the expansion of the inner oven sections while the outer render and your thin brick facing being way cooler. Also not sure how any tile adhesive will fare against the hot surface of the dome gallery. It will be way cooler than the dome itself so you could be ok. I think I'd coat the floor firebricks and the gallery castable with a concrete sealer before attempting gluing anything to it, though have no idea how it stands up to heat. You've come this far, I think you need to press on regardless.

[Lotus19]

Not much progress with the oven, as it's been rainy and cold the last month, but I wanted to give a shout out to our local pizza guy, Will Grant.

Ran into him yesterday, while we were both waiting at the barbershop (I instantly recognized him from the many times I've been in his pizza shop). Couldn't have been a nicer guy. We talked food, our little town and all things pizza for about 30 minutes. Even showed him some progress pics of my oven and got a thumbs-up. Ended up talking travel and he said he was heading to Portugal (today) to compete in the World Stars Pizza challenge, as the U.S. representative. How cool is that?!

Also excited for him, as it was his first trip to Portugal. My wife's family is from the Azores, so it holds a special place in my heart...

Anyway, just thought it was a cool story -- a global event, other than the World Cup, that all us pizza fans could cheer for!!


Will's bio and event info:

https://www.worldpizzachampions.com/will-grant
https://www.worldstarspizzaportwine.com/

[Kris S]

Hi Joe,

Your oven looks great!

About the edge of the hearth slab being too close to the oven mouth: I saw a post on this forum when I was doing my own research from someone who had the same problem and solved it by adding an overhanging self-supporting thin slab of concrete ( +/- 20cm deep or ‘long’) directly to the front edge.
He drilled some holes in the existing front to put some rebar in it so it would support the overhanging slab.