42” Corner Build in the Shadow of Mount Nittany

[Giovanni Rossi]

I know there is debate about using chicken wire or not and whether to wrap it on the blanket or embed it in the middle of the pericrete. Ease of application also comes down to mixing a proper consistency (this is yet another one of the build tasks that you need to do a few times to get a proper feel for it). I was glad I had the wire on the blanket for the first layer, especially at the bottom of the dome where I was working beyond vertical, inside to out, to preserve the shape of the sphere.

The kit instructions call for 2” of 5:1 pericrete. Since I knew I was going to run out of perlite, I decided to change the plan. I used 8:1 for the first ¾” layer and 5:1 for the 2^nd layer. The 3^rd layer would be about ½” without any perlite. My thinking was the insulation value would decrease and the strength would increased as I moved out from the center. Honestly, I doubt these layers will have much of an impact on heat retention given the 4” of blanket; but, I wanted a harder outer shell.

If you’ve followed this build, you know I was confused about the use of the term “render” and the use of fibers to add strength. I will add AR fibers to the final ½” layer, but I probably have enough fibers finish 10 ovens

I mixed 22 liters of dry mix at a time and worked in bands trying to keep a wet edge as much as possible. I believe I needed 6 batches to finish the first layer.

[Giovanni Rossi]

The company offers a temp monitoring set up that uses what’s called a Thermowell inserted into the dome and a thermometer that threads into the Thermowell. It’s designed to extend into the dome interior. I decided instead to place it an an angle and drill only part way into the firebrick such that the end of the probe is about 3” from the inside face of the dome. I hope this gives me an indication of heat saturation. The supplied door has a thermometer so I can also monitor the air temp.

[Giovanni Rossi]

UtahBeehiver and Gulf recommend placing a vent to allow any steam generated in the blanket layers to dissipate and not build up pressure against the render. I followed examples on the Forum. I found this hydraulic breather cap online. The guys say they are also available in auto supply shops.

I couldn’t for the life of me find a washer the right size to pinch the hardware cloth between the PVC fittings so I just clipped the mesh enough to thread the fitting into it. The assembly was then positioned at the top of the dome and tied into the chicken wire keeping the bottom of the PVC snug against the blanket.

[Giovanni Rossi]

I let the pericrete layers dry for about six days and then maintained a moderate fire for about 3 hrs before closing the oven for the night. Next day I took the oven to full firing and made 11 pizze for daughter’s bday. The keystone started clearing as the temp passed 800 F. The dome cleared during the baking. The fire had burned down quite a bit at the end of the night and I placed the steel door. The temp at the door registered 600 F and the probe in the dome was at 500 F. The temps the next morning were about the same. 24 hrs after closing the oven the door was at 500 F and the dome was 475 F.

Next steps: build a landing then apply the final render layer.

[MarkJerling]

Looking good! The inside of your oven looks amazing.

[Giovanni Rossi]

Thanks for the positive comment MarkJerling !

Starting on the granite landing...

Recycled from an old brick patio to build the landing support.

[Giovanni Rossi]

Learned a valuable lesson and I should have heeded the cautions on the Forum to not use old mortar. I had some left over Masons Mix Type S from when I layed the CMU footing last spring. It had a few lumps in it but seemed fine otherwise, mixed well and troweled fine. Well, it obviously took on moisture at some point and basically cured in its powdered state. The next day I decided to insulate between the floor tiles and the bricks. While doing that I dislodged one of the bricks! Turned out the mortar was “solid” but disintegrated to sand when disturbed. I had to demo the work and redo with fresh mortar mix.

I layed the bricks so there was an air gap between the brick and the floor tiles and the refractory heat bank layer. Then I remembered that I had quite a bit of FOAMGLAS leftover so I decided to fit some in that gap. Maybe it will slow the heat from bleeding from the floor??

[Giovanni Rossi]

Did a little dumpster diving at a local countertop fab shop and found enough granite scraps to fabricate a 3-piece landing. It was fun learning about cutting and polishing granite. I often write about my new favorite power tool…my trusty angle grinder. While it worked great using a diamond cutting wheel and a grinding wheel, the 11,000 rpm was too fast for the polishing pads. Had to buy an inexpensive variable speed one to finish the job. Probably can’t get any better than having 2 angle grinders.

[JRPizza]

NIce score on the granite!
For reference, what pads and compounds did you use for the polishing? I have some granite that was never finished properly when it was installed and could make some major points with the Wife if I could shine it up

[Giovanni Rossi]

There are options. I used a brand called STADEA. You work through 7 grit sizes, 50 to 3000. You use 3000-4000 rpm. I really wore down the 50 pad working the cut/grinding marks out of the edge. I rounded over the top edge and did a 45^o chamfer on the bottom edge. I stopped at 800 then laid the pieces with thinset. From what I read, should get some shine starting with 1000 grit. With them in place I'll work through the remaining pads. Haven't used any compounds. I'll see what it looks like after 3000 and go from there.

It took me a while to figure out the water supply since I didn't have one of those fancy power tools. Slow flowing hose was just a mess. I set up saw horses with a slight downhill slant. Then soaked a big grout sponge and laid it uphill from where I was polishing. The vibration "worked" the water out of the sponge in just the right amount.

[MarkJerling]

There are options. I used a brand called STADEA. You work through 7 grit sizes, 50 to 3000. You use 3000-4000 rpm. I really wore down the 50 pad working the cut/grinding marks out of the edge. I rounded over the top edge and did a 45^o chamfer on the bottom edge. I stopped at 800 then laid the pieces with thinset. From what I read, should get some shine starting with 1000 grit. With them in place I'll work through the remaining pads. Haven't used any compounds. I'll see what it looks like after 3000 and go from there.

It took me a while to figure out the water supply since I didn't have one of those fancy power tools. Slow flowing hose was just a mess. I set up saw horses with a slight downhill slant. Then soaked a big grout sponge and laid it uphill from where I was polishing. The vibration "worked" the water out of the sponge in just the right amount.

Your advice can't come at a more perfect time for me! I've just received some granite bowl cut-outs which I'll be using for plinths for my turntables. These will need their edges polished. Thank you!

[Giovanni Rossi]

I tried an experiment I hope doesn’t come back to haunt me. Some cracks appeared in the final pericrete layer that look to be cause by expansion of the arch bricks and/or the precast flue gallery.

Decided to glue ½” ceramic fiber rope around the exposed masonry with some high-temp silicone.
I’ll use this as curb for the final concrete render. Hopefully it will insulate and provide some flexibility between the masonry and the hard-shell render??

The last covering for the dome is a waterproof acrylic roll on/paint on render. I’ll extend this over the exposed surface of the rope to encapsulate it.

More to follow…

[Giovanni Rossi]

So far so good with the experiment after a full firing. The silicone held the ceramic fiber rope in position well and I was able to put a lot of pressure on it as I applied the final concrete render. This layer was 1/2-3/4” thick using a 4:1:1 mix of sand: portland : hydrated lime. I added 150gm of AR fibers to each 12 liters of dry mix and found it was easy to work and gave me the result I wanted.

Before that, I wasn’t happy with the roundness of the dome on one side so I used the remaining small amount of perlite fix that. I used all that pericrete but didn’t quite have enough. That allowed me to test out the AR fiber mix to finish. By my calculations from the answers I received on the Forum, I had come up with a proportion of 300 gm per 12 liters dry mix. I found that difficult to apply in such a thin layer especially as I had to feather the edges. Some of the difficulty was probably due to my still novice skills. Since I didn’t have to worry so much about slumping with the thin final layer and was just looking for some added strength, I halved the AR fiber amount and was much happier with the result.

Even after all of the work so far I am still amazed at the volume of material required to cover the dome. This last thin layer tested me physically (and mentally). I honestly lost track of the amount of render I mixed. My wife took over measuring and mixing the dry the ingredients or I may not have been able to finish in one session. I believe the total was around 70 liters of dry mix.

I wrapped the oven for a week per the recommendation of david s to get a good cure on that final layer.

I forgot the recommendation is to have 2-3 full firings before applying the final brush on render to be sure the masonry is completely dry so that waterproof render doesn’t blister. So, I just brushed some over the exposed ceramic fiber rope for now. I gave that a few days to dry and then fired the oven. I’m happy to report no visible cracks in the render, so I’m going to call the rope experiment a success.

I put a scratch coat over the brick support for the granite landing and will put the finish coat on as time permits.

[Giovanni Rossi]

I know some of the Forum members like to make their own oven tools so I’ll toss in this experience. I had an aluminum peel with a short wooden handle my father made me years ago for my gas grill pizza sessions. I was reaching my DIY limit and I wanted one with a larger blade and longer handle, so I just ordered one. I was worried it wouldn’t arrive in time for our next party this past Sunday so I tried to modify the one I had...the new one landed on Sat at 7PM.

I couldn’t find an aluminum tube longer than 36” at a local big box so I grabbed 2 of them. It took a bit of searching for a solution to join them and keep a smooth surface. The tubes are 3/4“ and I found a 3/8” stainless steel nipple with tapered threads on each end. I don’t have a tap large enough so I just used the nipple and some cutting fluid to make the threads in the aluminum. It took some time, but worked well. The rods tightened fast to each other.

I ended up using both peels and the joint held up well. Just debating on whether to add some thread lock or leave as is so I can change back and forth from short to long handles.

[xvandish]

That granite landing looks really nice, and agreed with Mark, the inside of your oven looks awesome! Hope you're getting great use out of the oven so far