36" Pompeii in DC

[mrchipster]

Re: 36" Pompeii in DC

So, humor me for a second here. I get that mortar will not make a very good bond with the insulation and aluminum, and so plain mortar would eventually crack and fall right off, same as the cement board is doing. But if I mix SS needles in, preventing it from cracking, and the SS nuts are on the ends of the bolts, where is it going to go?

Is my faulty assumption is that even with SS needles, 1/2-3/4" of homebrew will still crack, or is it something else that I'm missing?

You really have a fixation on trying to make your life more difficult, .75 inches of home brew will be very heavy, still very brittle at the edges, and not hold up over time. ie why not make residential doors out of concrete? Well because it is heavy and brittle and do not retain fasteners well under stress of movement. Moving things are rarely made from concrete. Usualy because of flexibility, moving items are made from wood, metal or plastic. And tempered glass is flexible just in case you thought of that as brittle. A thin sheet of stainless will be light, durable, heat resistant, non corrosive, flexible, and lastly will work.

But please, if you need to try it, go right ahead. And let us know how many cycles your concrete door lasts.

My metal door is over a year old and works just as well today as the day it was built, I have dropped it several times and on one occasion I even bent one of the corners, a pliers fixed it back to it's original shape, and have on average 3 firings a month and use it for 3-4 meals a week, each meal requires the door to be in and out several times.

Best of luck.

Chip

[rsandler]

Re: 36" Pompeii in DC

You are correct.
The stuff will just fall off after a while.

So, humor me for a second here. I get that mortar will not make a very good bond with the insulation and aluminum, and so plain mortar would eventually crack and fall right off, same as the cement board is doing. But if I mix SS needles in, preventing it from cracking, and the SS nuts are on the ends of the bolts, where is it going to go?

Is my faulty assumption is that even with SS needles, 1/2-3/4" of homebrew will still crack, or is it something else that I'm missing?

[brickie in oz]

Re: 36" Pompeii in DC

This is surely a terribly idea for some reason(s); I trust you all will tell me why?

You are correct.
The stuff will just fall off after a while.

[rsandler]

Re: 36" Pompeii in DC

Hmm, no one responded to the previous post. Is that an indication that it actually isn't all that crazy, or (more likely) that it's such an incredibly terrible idea that I have stunned you all into silence?

More likely, I will track down some stainless sheet/plate and use that. Maybe get two and put one between the outer cement board and the wood.

[rsandler]

Re: 36" Pompeii in DC

Riffing off of the end of the previous post, how about this for crazy idea #73:

What if I were to remove the remaining cracked cement board, while leaving the bolts and nuts in place and protruding ~1/2 inch from the insulation. Then I mix up a batch of homebrew mortar laced with stainless steel fibers/needles, and spread a 1/2-3/4 inch thick layer on the inside of the door. In principle, you'd have something like the homebrew equivalent of a layer of reinforced, dense castable refractory, anchored to the rest of the door by the protruding stainless steel bolts and nuts. In addition to sealing in the insulation and resisting heat, it would have some thermal mass to reflect heat back into the oven for baking bread.

This is surely a terribly idea for some reason(s); I trust you all will tell me why?

[rsandler]

Re: 36" Pompeii in DC

bingo!

BTW, your wood face not really holding up, it is slowly turning into charcoal.

Certainly; I meant "so far" and "in relative terms". I need to come up with a solution for that sooner or later (or else I'll need to come up with a new piece of wood!), but it is not a good stiff shake away from total destruction.

I agree stainless is ideal, un galvanized steel second and then aluminum.

So, supposing I do that, what gauge am I looking for and how do I drill it? The trouble I had with my door mark I (with aluminum back and front), is that the aluminum warped under the heat and, lacking much in the way of rigidity, failed to really hold the edge in place. On the other hand, I could drill it with a standard drill bit and some persistance. I'm guessing that stainless, especially stainless thick enough to be relatively rigid, will not be so easy. I suppose, since my new aluminum edge piece has a full set of tabs bent around the insulation, I could use aluminum go for rivets this time, although I'm somewhat disinclined to do so.

I might try applying mortar as a temporary quick-fix; given that the inside of the door needs to withstand heat but isn't getting much physical punishment, perhaps it would hang in there for a bit?

[mrchipster]

Re: 36" Pompeii in DC

bingo!

I doubt homebrew will hold up either. It has no shear strength, it will likely crack and fall off too.

Find a piece of scrap metal - preferably steel - and cut it with a jigsaw blade.

BTW, your wood face not really holding up, it is slowly turning into charcoal.

I agree stainless is ideal, un galvanized steel second and then aluminum.

The cement board will be temporary no matter what you do.

A cutoff wheel on an angle grinder also works well for cutting curves on sheet metal.

I agree with DJ a full burn on the outer surface of the door is just a matter of time.

Chip

[deejayoh]

Re: 36" Pompeii in DC

Is cement board not suitable for these temperatures?

bingo!

I doubt homebrew will hold up either. It has no shear strength, it will likely crack and fall off too.

Find a piece of scrap metal - preferably steel - and cut it with a jigsaw blade.

BTW, your wood face not really holding up, it is slowly turning into charcoal.

[rsandler]

Re: 36" Pompeii in DC

Ironically, the wood is holding up so far, even after two long, hot burns for a pizza party this weekend (a pre-heat the day before, then a long fire the day of). The cement board, not so much :P



Not sure what happened here; some chips of cement board had broken off previously and somehow wedged between the inner piece and the insulation, forcing the board away from the insulation. When I tried to fish the bits out last week, the board cracked a little bit. This weekend, I turned the door upside down to try to shake the bits out, and the sections of board cracked and fell off instead. The top piece that's cracked in the picture broke off shortly after.

What happened here? The cracks run between the bolts (and the top bolts are still partly holding the board on, a result). Did I tighten the bolts too much? Is cement board not suitable for these temperatures? The cement board-CalSil sandwich is what FB recommends in the Pompeii plans, though it seems that hardly anyone does it. Was the board just damaged, and once it chipped and the chips got wedged into it, the thing was doomed?

More to the point, how do I fix this thing? Start over? Just replace the inner board, don't tighten the bolts as much? Cover the exposed area with homebrew mortar? Could also parge the whole surface with homebrew, I suppose. I still have a bunch pre-mixed homebrew sitting in my garage. Just leave it? The insulation is still mostly covered by the aluminum tabs, the tabs are held down by the remaining cement board, and the bolts continue to hold it all together...so far.

[mrchipster]

Re: 36" Pompeii in DC

Yeah; I guess that's a good start for where the door may not be sealing well. Hopefully it doesn't do much more than char.

Be prepared for it to burn; char will easily turn to burn at some point. And highly likely after placing the door on after a long hot burn like a large pizza party.

I placed my decorative wood face on metal and cut it back so it is protected by the insulation layer and metal

Note that I still get heat coming thru the door and heating the area around the handles. The door is filled with 4 inches of ceramic board. The handle supports do go all the way thru to the interior so there is some heat loss there. Something I will fix at some point.


Chip

[rsandler]

Re: 36" Pompeii in DC

Looks like the wood is getting a little hot near the top and lower corner...

Chip

Yeah; I guess that's a good start for where the door may not be sealing well. Hopefully it doesn't do much more than char.

[mrchipster]

Re: 36" Pompeii in DC

Looks like the wood is getting a little hot near the top and lower corner...

Chip

[rsandler]

Re: 36" Pompeii in DC

Also, some better pictures of the working parts of my new door:





To put it together, I clamped the hardiboard and CalSil to the wood, and drilled holes through the board and insulation just deep enough to make a mark on the wood. Then I took the whole thing apart and used a countersink bit to make recesses in the wood for the bolts. Next, I put 3" SS bolts through the outer piece of hardiboard and lined it up with the recessed holes in the wood, and used hardibacker screws to screw the cement board to the wood. As a result, the outer piece of hardibacker is flush with the wood, but the wood is not in direct contact with anything that will face the heat of the oven. Well, there's probably some contact with the heads of the bolts, but not much. The handles are then screwed just into the wood, and never get hot.

Then I put the CalSil onto the bolts, used some pumpable ceramic insulation to fill the holes from the first incarnation of the door, and then put the inner piece of hardiboard on and tightened the nuts to hold the whole thing together. As a finishing touch, I used the pumpable ceramic to cover up the ends of the bolts to reduce the amount of heat transfer.

The oven rope in the pictures is not actually attached--I stuck it on over the weekend as I was slow-roasting a brisket, to see if it would help with the heat loss I've been experiencing. No idea if that worked, but it seemed content to stay put, and I haven't gotten around to adjusting it and cementing it down.

[rsandler]

Re: 36" Pompeii in DC

And here's the landing counter, pics attached.

I'm satisfied with how the landing turned out, but not nearly as happy as with the prep table slab. If I had it to do again, I'd have figured out some way to pour it face down. In part because it was hard to screed and in part because I'm a lousy hand with a trowel, the initial surface was very rough, and uneven to boot. Even after two slurry coats, there were still a bunch of dings and divots that I just gave up on. On the other hand, I can already see that the landing will frequently be coated in ash and gunk from the fire, so maybe I shouldn't worry about it too much.

I ended up continuing the orange them here, although again unintentionally. This time I knew that whatever color the slurry started would be the color it stayed, but the slurry looked browner in the mixing tub, and turned orange as I started rubbing it in :P. Ah well, now I've got a them. And it goes with the terracotta red flue tile. If I admitted that I goofed on the color, you'd think I planned it.

I guess now the tile mosaic for the dome will need to use those colors: brown, orange and flecks of blue. Any suggestions on designs?

The finished product:

[rsandler]

Re: 36" Pompeii in DC

Lots more work on the counters. Pics attached for the prep table.

This didn't turn out at all how I expected, but I'm really happy with the results. The bright orange color of the slurry was the result of me mistakingly thinking the slurry would lighten as it dried. Word to the wise: slurry made with white portland cement does not change color when it dries. Live and learn... Still, the brown/orange/blue mix, actually works. As my wife put it "I know that wasn't what you were trying to do, because I can't imagine you trying for orange, but it actually looks pretty cool."

I shelled out for the Cheng brand sealer, which after two coats keeps moisture out of most of it. Also applied a very thin coat of Cheng wax before I got fed up with the cheap buffer bonnet I bought and called it good enough. I did discover that after a couple days of constant, drenching rain there were a few spots that "wet out" despite the sealer. Wondering if I should buy another bottle of sealer and re-seal, and if that will even work through the wax. I guess if water gets through, the sealer should too, right?

Pics of the landing counter to follow...