Difference between Colle oven and Pompeii oven dome

[sledge]

First off let me say -- what a great forum!!! Glad I came accross this. Thanks everyone!

I'm in the initial stages of planning to build an outdoor "beehive" fireplace -- as they're called here in Arizona (but are really more like a Kiva). I'm hoping to make it a dual purpose fireplace incorporated with an oven.

When I look at the pictures of the Colle oven and compare them to the instructions for the Pompeii oven there is a distinct difference in the starting course. The Colle does not have the first row of brick standing on end with the 2 1/2" face, facing inward. It seems to have a starting row exactly like all the other courses. Is this in fact truly what I'm seeing?

Is there a specific reason for this or simply just a different design? Is the size of the brick used in the Colle oven the same as the pompeii -- 4 1/2" (9" cut in half). It's hard to tell from the picture.

Also, can anyone tell me about how many 2 1/2" x 4 1/2" x 9" brick are required to build the dome? Preferably the Colle one -- as I like the looks of that one the best.

Thanks again!! I'm looking forward to learning more (and posting my pictures!)

[james]

Thanks Sledge,

I've stuck my head inside a lot of handmade brick ovens, with and without fires , and I would say that a majority of them have the first course standing on its end -- though of varying heights. In a sense, the height of the first course is one of the factors that defines the shape and curve of your dome.

That also tells me that there isn't a right or wrong way of doing it, as long as you get the dome shape and curve that you like.

The standard Pompeii plan calls for the dome set on the cooking floor, and the first course is a standard brick cut in half and set on its edge (with the cut side down).

The 42" oven has about 180 bricks in the dome. Can anyone confirm that? Also, how many bricks are on the cooking floor?

James

[sledge]

Okay, thanks James. I'm catching on a bit more...all in how you lay out the dome. I've spent a bit more time looking through the forum here and I'm getting a bit more info to sink into my thick skull!!

Also, a post in the thred "does anyone make special cuts in the bricks other then at the top of the dome... " by Cookinghomer really helps with the brick count. He has a CAD drawing that shows about 70 bricks in the floor and then the base circle of halfbricks. This really helps.

I've got more engineering to do regarding the smoke throat and chimney for the kiva before I can really get started building.

I'll be back!!

[ColonelCorn76]

Yes there is a reason for the side wall bricks the way they are on the Pompeii is to get the arch into a parabolic shape vs. a hemispherical one (creating a catenary curve). That gives the oven the ability to hold its shape without a lot of external supports (if you've ever seen an Alan Scott oven, it requires about 4" of concrete cladding to help keep the oven walls & dome together).

This results in a Tuscan style oven which is good for both the optimum cooking of bread and pizza (vs the flatter domed pizza-centric Napolitano design). But, the use of the standing bricks (4.5" high vs. the 2.25" of a flat brick) doesn't have anything to do with the way the oven looks from outside. All of the aesthetic photos are of the exterior of the oven which has no material relationship to the use or non-use of the standing side wall. You can make any internal oven design look like the Colle oven in the FB site.

Check out my photos at photos.yahoo.com/colonelcorn76 for one look.

Jim

[ColonelCorn76]

Hearth bricks

By the way, I'd recommend using a herringbone pattern for the hearth. Parallel rows of bricks is traditional but result in continuous joint lines stretching across the oven. Peels can catch on these so I perfer the herringbone pattern instead. That keeps from creating a the potential for a lip to catch a peel.

To do the herringbone design, you find the center of the oven and snap your cross lines so you've got a circle with a + in it (snap the line on your fireclay & sand mortar bed). Take your first firebrick and carefully place it so the upper right corner is in the center of the + lined up with the vertical & horizontal lines of the +. Lay 2 more bricks along this line, one closer to the front & one closer to the back of the oven. Then mark your 1st firebrick's middle (4.5" for a 9" long brick). Take your 4th brick and line up the bottom edge with the middle mark on the 1st brick. This offsets the 2nd row of bricks by a half brick. Place another brick on either end of this latest brick.

Now for your 3rd row, you're going to line up the top edge of the brick along the horizontal line of the + (the vertical one is between rows 1 & 2 and doesn't show anymore). This lines the latest brick up with the 1st row's bricks. Then you just repeat this over & over until you've got the circle (51" diameter for a 42" oven) covered with bricks. (If you're really a perfectionist you can cut the outer bricks to the actual curves of the circle, otherwise just make sure the bricks cover the circle and live with the extra parts outside...they'll be covered by whatever housing you put over the oven.)

Your hearth ends up with brick lines that look like this: -_-_-_- which will tend not to catch your pizza peels (especially the metal ones).

Your brick count will depend on your hearth floor style.

Jim

[paulages]

nice pictures jim!

[ColonelCorn76]

I love seeing what other folks are doing with theirs. I started out with a basic design hoping others could build it (James just wanted a brick-oven in every backyard...like Webermania) and I'm amazed at what some folks have done. Anyone who says craftsmanship is dead in this country has got to be talking about things that evoke no passion. Everyone's doing great work out there.

Jim

[sledge]

Great! Thanks for all the info. Unfortunately, due to a local block shortage here in the Phoenix area I have to wait another two weeks for delivery of my supplies, so can't get started yet.

Jim, did you really mean a "herringbone" pattern for the floor? I'm not sure that, that is what you're describing in your response.

Is it like the picture below?


I certainly like that pattern for the floor, but can't say as I've seen it used on any of the other ovens I've looked at.

Would'nt this pattern use more bricks?

Also, anyone have a good source (online) for the vent and chimney parts? I see that many of the ovens have a metal vent that sits on the lintel -- where do you get these?

Kevin

[ColonelCorn76]

Oops. You're right. My bad -- the pattern is actually called a running bond pattern. Your photo is a true herringbone. What I was describing is this one.

Thanks for picking that up.

As for the vent, I can toss you the drawings for building your own (if you can weld).

[sledge]

Okay...got it. I don't know though, the herringbone deal looks pretty cool! I've since seen a couple fireplace websites that had that pattern on the back and side walls...haven't seen it on the floor though.

I'm not a welder, but I can weld...if you know what I mean. The vent is pretty much covered up anyway so no one would see my not so good looking welds, right?

I took a look at your pictures...very neat by the way...and see your vent. So, you just welded it all together yourself? Looks straightforward enough. I'll most likely wait until I get closer to figure out what I really need. Was just wondering what was commercially avialable. I may take you up on the offer for drawings...but later. I'm still toying with the idea of making the whole oven enclosure also serve as a smoker. Hmmmm...not sure how to do that exactly. Will require more thought. I still have another week to wait until block is delivered as there is a shortage here in Phoenix due to all the construction.

Cheers!

[paulages]

i think the herringbone pattern makes the most sense, as it it designed to have as few running seams as possible. i did my floor in something of a herringbone pattern, but mostly was trying to cut down on seams perpendicular to the "in and out" dierection of the oven.

[Marcel]

Many and varied unrelated oven questions

I hope that I am not abusing the posting protocol by posting so many unrelated questions but all of them have to do with oven construction. If James reads this, please let me know if you would have preferred my starting a new "thread". If you reply to any of my questions, would you kindly number them as I have? Thanks.

The clearest construction photos I've seen are those of Jim Hatch ( Col. Corn) on his Yahoo Site, photos.yahoo.com/colonelcorn76

1- I am using those for planning, such as counting the number of concrete blocks, etc. If anyone knows of additional clear photos I would be glad to supplement my resources __________

2- I will pour 3,000 psi transit delivered concrete into a 10'x10' form of 2x6. I have laid down 3/8th in re- bar, 2 sticks about 6" apart only on the perimeter where I estimate the block wall will later rest. I have been told that the placement of the re-bar is not critical. Your comments? _____

3- The block wall will be placed, when facing the first slab, at the extreme rear and as far left as possible. This placement is to allow us some extra slab on the right, and a front apron of perhaps 40"? Is there any problem anyone sees in situating the walls off center? ______

4- I am trying to plan way into the future as sometimes the later steps hinge on the initial ones in ways I wouldn't otherwise foresee. I notice an angle iron which supports the arch opening bricks. Is there any reason I should not make relieving V cuts and bend that angle iron to conform to an arc of the 42" circular floor? ____

5a- Different builders have modified the curve of their domes; parabolic, and hemispheric. I am drawn to the hemisphere. If I place the first course of firebrick on their shortest edge, is that first course set up so that the maximum width is utilized for greater thermal thickness? ____________

5b- Do I place the first course of soldier bricks on the herringbone circular base firebricks, or next to the perimeter of that circle? ___


6-If I proceed as above, and want to construct a hemisphere, presumably only the outside "cladding" would approximate that profile. If I use the styrofoam temporary bracing for the firebrick and cut those styrofoam supports in a true hemispshere, and place them *on* the first "soldier" course, will I end up with a dome too high because the first row (course?) becomes a part of that so called hemisphere? _____

7- I would like to post images on the forum. Mary's camera seems to provide too high a resolution for the forum to accept. Is there a way to reduce the file size within the forum tools? ____________

That's about all I dare to ask out of context but I know I'll have many more questions as the building progresses.

Ciao,


Marcel

[Robert Musa]

Marcel, sounds like you're covering all the bases. A few responses:

5a. is that first course set up so that the maximum width is utilized for greater thermal thickness? all courses are half bricks. the oven walls should have a uniform thickness from top to bottom.

5b. Do I place the first course of soldier bricks on the herringbone circular base firebricks, or next to the perimeter of that circle? on top of. the ragged edges of the base will extend beyond the circle circumscribed by the outer edge of the first course.

6. will I end up with a dome too high because the first row (course?) becomes a part of that so called hemisphere? not necessarily, if you angle the remaining courses correctly. my dome ended up a few inches too high (which is preferrable for roasting and seems to work fine for pizza as well).

7.Is there a way to reduce the file size within the forum tools? i defer to james but i don't think so. a quick and easy way to copy a folder full of photos into a new folder with much smaller pictures is by using the export feature of the free picasa software available at http://picasa.google.com/index.html

[paulages]

marcel,
i might be able to help answer a few of your questions as well...

1. i have taken some pretty detailed photos of my construction. i have limited which ones to post, so the thread is not enormous, though my pictures are not actually in the forno bravo database, but rather hosted by another site. if you would like to see specific sections, just let me know. i'll probably organize them at some point and post a link to all of them.

2. I would place rebar wherever there will be a significant load, but if you are not digging a deeper footing where the block stand will actually sit, i would place it throughout the whole slab. actually, rebar is cheap---i would just over-reinforce it if anything.

3. I'm not sure if i completely understand your question, but as long as there is significant reinforcement in the hearth slab and your hearth is sitting firmly on the block stand, there shouldn't be a problem. just make sure the stand is evenly taking the load.

4. cutting either face of angle iron will comromise it's strength significantly, unless you weld each cut back together after bending it. even then, it will likely not be as strong, unless you are a proficient welder.

5b. most people place their walls on top of the floor, because the floor is layed out roughly, with the jagged edges extending beyond the walls. however, i cut my floor round, and placed the walls around the floor instead, believing that this would make it harder for heat to escape beneath the wall. i can't speak for the other method, but this way worked well for me. the very bottom of my wall on the outside (the ones butting against the sides of the floor bricks) is about 50 deg. cooler than 3 or 4 inches higher, where they actually face the interior of the oven on the inside. also, this way heat is not escaping through the protruding floor bricks.
but this does require the added labor of cutting the floor bricks round.

6. when you lay out your bricks on the ground to decide the shape of your dome, just include this first taller layer in the cross section, and then proceed to make it however high you want it.

7. i download my photos onto photobucket.com (it's free), then copy and paste their html link onto my posting. this doesn't take up any space on forno bravo, but rather loads the photo from the host whenever you view it on the page. you could do the same with yahoo, or anywhere else that does photo hosting for free. the disadvantage would be fornobravo not having them in their database if the host ever went down.

good luck with your oven!

[ColonelCorn76]

1- I am using those for planning, such as counting the number of concrete blocks, etc. If anyone knows of additional clear photos I would be glad to supplement my resources __________

===> Check the files section of the Yahoo group. I posted a block diagram that has a page for each layer and a block count & size by layer.

2- I will pour 3,000 psi transit delivered concrete into a 10'x10' form of 2x6. I have laid down 3/8th in re- bar, 2 sticks about 6" apart only on the perimeter where I estimate the block wall will later rest. I have been told that the placement of the re-bar is not critical. Your comments? _____

===> Wow. Transit mix in that small a batch is really expensive here. I went the bags of Quikrete along with a mixer rented for a couple of hours. As for the rebar, place the first row about 3" in from the edge and then the next parallel ones about 2" further inside. You can get rebar mounts which are little wire saddles with depressions to lay the rebar into that you can lay them on. You'll have 8 pieces of rebar -- 2 on each side. Over that, I'd recommend a layer of mesh but since it comes in big rolls, see if you can get some wire fencing with the 2x3 inch grid pattern (or something close). Lay that on top of the rebar & tie it all together with twist ties or those plastic zip ties.

3- The block wall will be placed, when facing the first slab, at the extreme rear and as far left as possible. This placement is to allow us some extra slab on the right, and a front apron of perhaps 40"? Is there any problem anyone sees in situating the walls off center? ______

===> Not me. Just slope it a bit to keep the water from rain from flowing into your wood storage (if you plan on using the underhearth space for storage).

4- I am trying to plan way into the future as sometimes the later steps hinge on the initial ones in ways I wouldn't otherwise foresee. I notice an angle iron which supports the arch opening bricks. Is there any reason I should not make relieving V cuts and bend that angle iron to conform to an arc of the 42" circular floor? ____

===> You can. Not sure it's worth the effort. Also, the straight piece makes for a nice flat backing for the chimney vent and a flat face for the door you'll want to build for cooking bread or slow-cooked roasts/turkey/etc. The cuts weaken the steel but it's not structural in the sense of long term support of the bricks. Once the mortar sets up, those bricks that rest on it will be fine even if it disintegrated.

5a- Different builders have modified the curve of their domes; parabolic, and hemispheric. I am drawn to the hemisphere. If I place the first course of firebrick on their shortest edge, is that first course set up so that the maximum width is utilized for greater thermal thickness? ____________

===> The Pompeii is a section of a parabolic spheroid. That's typical of Tuscan ovens which are suited for both bread & pizza. A true hemisphere is not as efficient in drawing the air & washing the full surface of the dome with flame & smoke for most efficient transfer of heat (conduction, convection & radiation). A hemisphere is also not as strong in holding the arch as the force vector pushes outward more than downward. The parabolic design redirects the gravitational forces downward as the ancient cathedral builders found with flying buttresses.

5b- Do I place the first course of soldier bricks on the herringbone circular base firebricks, or next to the perimeter of that circle? ___


===> On top of. Butter your mortar all the way down and you'll have an airtight and thermally efficient bond. Paul did his by cutting the inner hearth bricks in round slices and placed the soldier bricks outside the hearth bricks. That's a lot more work but doable. I don't believe there is a significant difference in performance of the oven.

My answers are instream with ===> in front.
Jim