BeanAnimal's 42" build - Pittsburgh PA

[BeanAnimal]

I think it's safer to cure the oven after doing the vermicrete layer and before doing the outer render, because the vermicrete contains so much water the steam pressure can crack the outer shell. Waiting at least a week to let the sun and wind dry this layer is also advisable. However you should probably follow the instructions given by the manufacturer of the kit.

The kit assumes insulation blanket, rendering with 2" 5:1 of perlite concrete and then waterproofing with a (supplied) roll on acrylic.

Because I am building a house around the dome, I don't see the need for the waterproofing and am not sure I want to even bother with the perlite render - unless there is good reason to do so.

I guess the big question is - just add more blanket or is there a good reason to do add the chicken wire and perlite render?

[Kvanbael]

first of all: your oven looks great.

I’d think a heater doesn’t harm as long as it has a thermostat. And it shouldn’t replace a curing day.

I am one of those that started curing before vcrete, and now I am wondering if I should start curing all over, or maybe from day 3 or so. As those first fires hardly warm up the Outside of the blanket.

[BeanAnimal]

first of all: your oven looks great.

I’d think a heater doesn’t harm as long as it has a thermostat. And it shouldn’t replace a curing day.

I am one of those that started curing before vcrete, and now I am wondering if I should start curing all over, or maybe from day 3 or so. As those first fires hardly warm up the Outside of the blanket.

Thanks for the kind words - plenty of flaws - I mean beauty marks! I really gave up on preventing mortar stains inside the dome and floor. I have set enough stone and tile over the years to loathe the process of cleaning up haze and grout embedded in nooks and crannies - I embraced the rustic look on this build and have no regrets - that and I have saved the frustration for the stone veneer that will look like hell with mortar mess on it.

I am going to follow the curing schedule provided - and likely even more conservative than that. That is the reason I thought about adding the heater now - in hopes of being even more conservative. I know cracks are virtually impossible to prevent, but I want to minimize them as best as possible.

[Chach]

I filled my enclosure with perlite and I purchased it through a company called Silbrico here in Chicago but they also have a location in PA

Silbrico
4250 EAST BRADEN BLVD
EASTON PA 18040.

1-800-323-4287

They sell direct to this public here in chicago and it was much cheaper. Just an FYI

Ricky

[BeanAnimal]

Thanks for the info!

I am not so sure that I want to backfill with perlite - I have to assume that doing so delves deeply into diminished return territory, especially given my 6" slab with 2" if CalSil. I have several cubic fit here that was to be mixed with the cement/lime - just debating if I should use it or just add a total of 4" of blanket.

[UtahBeehiver]

Adding additional insulation over the current 2" ceramic blanket,whether it be additional blanket or p/vcrete depends on how you plan on using the oven. 2" ceramic blanket is the minimum amount of insulation. If you envision multi-day usage then additional insulation (your choice) will aid in conserving the dome heal, you are already good with the combination CaSi and p/vcrter floor insulation. Since you already have the materials for a p/vcrete dome why not use them.

[BeanAnimal]

Adding additional insulation over the current 2" ceramic blanket,whether it be additional blanket or p/vcrete depends on how you plan on using the oven. 2" ceramic blanket is the minimum amount of insulation. If you envision multi-day usage then additional insulation (your choice) will aid in conserving the dome heal, you are already good with the combination CaSi and p/vcrter floor insulation. Since you already have the materials for a p/vcrete dome why not use them.

Actually the floor is just 2" of CalSil - the layer under it is refractory castable (airset) to act as a heat bank. I wanted to add more CalSil but got impatient to start the build.

I ordered 1 more inch (for a total of 3") of blanket.

I plan on holding as much eat as I can for residual cooking - why not

At the same time, I don't have any desire to just keep adding cost and insulation and labor for little return.

[UtahBeehiver]

A lot of ovens function just fine with 2" of CaSI under the floor, you just might have to do a short recharge of the floor if you host a large party.

[Chach]

I don't have anything to base my exoerience with the insulation I have which is 1" fomglas 2" calsil and 3" if ceramic blanket. I also then filled the enclosure with perlite. It has been 72hrs and im still a touch over 300 degrees since my last fire..Not sure how much the impact my perlite fill has but so far I'm happy and I dont have a legit insulated door yet. Just something for you to base your descion on.

Ricky

[BeanAnimal]

The moment I skipped the extra floor insulation, I regretted it - but what is done is done. The added dome insulation should help I guess.

I suspect I will place the perlite render tomorrow, as adding perlite as loose fill will require vastly more. That and it can always be poured over the render if I feel I must have it.

I got all 3 layers of blanket installed this afternoon and held down with chicken wire. The stuff that came with the kit is MUCH higher physical quality than the stuff I ordered from skyline components. I have no idea how they compare in regard to insulating quality. The china stuff is rather delicate, much more friable and much easier to compress. Both are the same density.,

[BeanAnimal]

Photos tomorrow....

I contemplated adding a 4th layer of ceramic blanket, but simply do not want to wait for shipping or track down overpriced local supplies. I have no idea where the point of diminished return is.

i decided to just go ahead and apply an inch or so of perlite render, mostly to secure the ceramic blanket fibers. I was not overly careful about neatness or shape. I got a late start and finished in the dark. Tomorrow will be interesting.

Anyway, I am ready to start curing and move on to the enclosure.

[UtahBeehiver]

Just a word of caution, this is the point where we have seen a lot of builders, in their excitement, fire too fast, too hot and damage their ovens. So as I always say, the turtle wins the race in curing. You can easily start with charcoal briquettes for a couple times. This will get you around 200-250 F and you can cook something dutch oven while you at it. When you move to wood, that one extra piece of wood can easily spike the temp too high. If you see steam coming off the oven you are going too fast.

[BeanAnimal]

Thanks Utah - I certainly plan to take it easy on the cure and am in no hurry to get this thing up to full temperature. I want to minimize the inevitable cracks that are sure to appear in my hard work. It will take me most of the summer to finish up the stand, floor area and repair the yard, fence and build the timber frame. If a pizza comes out of this thing before the final blade of grass is put back, she will lose her mind and I may be murdered in my sleep. I am going to have a hard enough time with the curing fires being part of the build and not me failing to finish in favor of use. So I will take it very slow. To her credit - I have a tendency to get things done just enough to make them useful - Hrmm, now where is that last trim board for the 7 year old home theater or the trim for the beadboard porch ceiling, or the trim for the basement bar or....

You see, my provisional building permit was issued on a "must COMPLETELY finish before use" clause.

[GreenViews]

Bean, Yeah, lol, we all have those projects which never quite get completed. Regarding curing, after 2 nights of 6 hour warming candles of about 200F, I tried to make a 300F fire with twigs. This proved to be too challenging to me and I ended up more like 500 F for much of the day. Besides not being sure if goal was 300F at wall or top of dome or what, it was very hard to keep such a small fire going (tried with or without a fan). There are a couple mortar joints which dropped a little (of Acona brand refractory) mortar on one side of my oven. It probed it with a trowel tip this morning and peeled back the outside to view and nothing visible on outside and about 1/4" deep at most on front side. I was surely too hot too fast. No real harm and I can go back later and patch these, but just a warning from my process. My fire skills were not sufficient to keep fire down to 300F. Today I will switch to charcoal like many have suggested! That I think I can control better, lol. The good news is my oven is keeping temperature well and I am at 270F at top of dome this morning and 220F at floor, without having an insulated door. Tom

[BeanAnimal]

Thanks for the update! Glad to hear there is minimal cracking or damage. I have not had a chance to start curing fires yet - I just can't find the time and have instead used the spare time to continue working to complete the oven.

Sadly, I have not had time to update this thread.

I also realized that I did not take any photos between insulating and house construction, so there are no photos of the overall perlite render process or final result. Ohh Well.

I ended up with 3" of blanket - kicking myself for not going with 4" - ohh well.

The entry area will also be insulated - but I wanted to get the structure in place first.