pompeii oven construction began today

[paulages]

the downside...

unfortunately, now i have to take it apart, apply the dry mortar and reassemble.

[paulages]

"excessive labor" out the window...

first cut at 7:45 pm


8:13 pm

8:30 pm

45 minutes from start to finish! so much for this taking forever to do. it was incredibly easy! i rented a paver saw from home despot. it did cost $37 for 4 hours, but i used it to cut all of my 9"x6" bricks to size as well.
if anyone is interested, i can post pictures of how to make these cuts, but it's really not so hard to figure out if you haven't done it before.

[paulages]

i have thought about facing the 6" side in. it makes for less of a graceful curve, and means that the next course would intersect it less smoothly. i'll try laying a few up though, and see.
i was afraid 6" thickness might create too much thermal mass. these bricks were cheap enough that, though it would be extra effort, i could whack 2" off of the back of each one with a brick cutting chisel, and still get both. i won't be using these bricks for the whole oven.

[james]

Paul,

I would think about pointing the 41/2" edge out, and the 6" edge in. That would give you a 4 1/2" thick dome, and the possibility to doing a little more cutting to make the 6" inward sides fit better. I'm a little concerned that 6" will impact heat up time.

Most refractory residential ovens are 2"-3" and commercial ovens are about 4"-5" thick, and they are fired 365 days/yr. Heating up a 6" oven from a standing start might take longer than you would like.

Food for thought.

James

[paulages]

found firebricks

well, i couldn't find low duty firebricks, but the medium duty bricks i did find have a fairly low silicon/alumina ratio. the guy ended up giving me a great deal on 2.5" x 9" x 6". he had a palette of 90 that had been sitting around for years, so it worked out well for both of us.
cut in half, this will just mean 6" walls instead of 4.5". and it also means fewer seams in the oven floor.
he also has a great selection of archway firebricks in the same grade, which will make the archway much easier.

[paulages]

firebrick types

i've been unable to find a low duty firebrick here in portland. the closest i've been able to find is a medium duty made by carter (info found@ hwr.com, under the product datasheets). they are $1.50 a pop. other than what's listed in the firebrick primer, anybody have any advice? i'll keep looking, but wonder whether i should settle for the medium duty at that price...

[paulages]

thanks bob,

yeah, i'm trying to round up some firebricks today, so i can work on this over the weekend. otherwise i'll have to wait until tuesday. i'm thinking of incorporating a BBQ into the design, just because it seems like there will be a lot of wasted space, even with a 42" interior.

[Bob C]

Paul,
It looks as though you're off to a grat start! Now the fun stuff begins.
Good work!

Bob C.

[paulages]

except for the belgian monks...

who make great beer.

[ColonelCorn76]

Everything to excess. Moderation is for monks.

[paulages]

hearth with stain

(and bird poop!!!!)
damn robins.

[paulages]

woohooo!

the insulating perlite concrete layer...

and the thermal/structural concrete layer.

i sprinkled in a red concrete dye before the final trowel, just in case i end up not tiling the front shelf. i had it laying around anyway.
by the way, i used steel wire ties between each 2 x 6 and it's opposite to keep the forms from pushing outward with the weight of the concrete and it worked perfectly. the corners are just screwed together. oh yeah, and i staked 2x4's underneath the top form all the way around so that the form would sit flush with the edge of the block stand.

[ColonelCorn76]

LOL! No cheating.

Bob (I think) did a cantilevered design with his hearth so the 3 1/2" overhang you've got going should work very well. No issues about the leveling of the block walls - just get the top of the hearth forms level and the hearth will be spot on.

Jim

[paulages]

thanks, jim!

okay, now that you posted that, i feel really lazy, like i was trying to cheat my way out of a 6th grade math test. thanks anyway.

here's today's labor:
note that i am creating a 3 1/2 inch overhang on the front (though this may be almost negligable when i veneer the wall underneath it...in any case, it gives me a bit more hearth space, where i couldn't quite afford it in the footprint.)
also note that, despite the foundation and first course of cinderblocks being level, somehow it didn't end up that way by the time i reached the top of the block stand. i decided it would be easier to fix with the top forms for the hearth, rather than adding mortar in the block stand to make the top course level, so that's what i did. i filled the large gaps between the block stand with duct tape. the exposed tape will never be seen, as the back three sides of the hearth will be covered by the veneer walls in the end. i caulked the crack on the front side, as this will possibly be the only place you will actually see the edges of the hearth, so i wanted the bottom edge to be smooth.
-paul

[ColonelCorn76]

Here's the post I did on the same subject on the brick-oven Yahoo group (for someone building an Alan Scott version but it works for the Pompeii too):

It's dependent on your specific installation -- hanging hearth, not
hanging, more custom stands (like fieldstone, etc.) change the size of
an individual installation. But, it's easy enough to calculate. Take
the width multiplied by the length of your forms (inner dimension),
multiply that by the height in those forms you're using for your
insulating hearth (e.g. forms are 2x6 which are really 5 1/2" tall but
you're going to have a 3" insulating layer & a 2 1/2" hearth layer --
you'd use 3" for the height). Convert to cubic feet & round up. That's
the total cu ft of the slab. Divide by 7 for the number of bags of
Portland and the rest is vermiculite or perlite.

Example:
Hearth slab of 6'x7' with a 3" insulating layer

Calculation is: 72" x 84" x 3" = 18,144 cu in
Divide by 1728 cu in per cu ft = 10.5 cu ft
Round to 11 cu ft (insulating hearth volume)

Divide by 7 (1/7th of the slab is Portland) = 1.6 cu ft of Portland or
1.6 94lb bags of Portland
Multiply this by 6 (6/7ths is vermiculite) = 9.6 cu ft of vermiculite
or 3 bags of vermiculite in 4 cu ft bags

So, you'd buy
2 94lb bags Portland
3 4 cu ft bags Vermiculite (or Perlite)

You'll have some of both left over. The extra Portland can be used for
the brick mortar when you build the dome and the extra vermiculite can
be used for insulating the dome. Adjust the calculations for your
specific hearth size.

Jim