Bricks required for a 43" oven

[Hendo]

Hi there.

I come from a land down under (as the song goes), and after much procrastination, I am planning to build an 1100mm (43.3") Pompeii style brick oven. To date, I have spent many fruitful hours gaining valuable information and ideas from forum contributors, as well as reading Russell Jeavons? book "Your Brick Oven" (The Bread Builders is on its way across the Pacific).

1) I note that the materials list for a 42" oven specifies 100 bricks for the floor - is this for bricks laid on edge or on the flat?

2) For the dome, 180 bricks are specified - does this refer to the total number of whole bricks @ 9"x4"x3" that need to be purchased, or is it the number of half bricks which actually form the dome? I assume the former, but wanted to check before ordering.

Thanks for setting up such a fantastic resource - I only hope I can contribute to it as this project progresses.

Cheers, Paul.

[KISS4me]

Snap in Aust.

Paul
Read your message about brick numbers. It sounds like you are at the same stage as me and using the same 2 resources - Russell Jeavon's book and this forum. My design is ia blend of these two references. I am still sourcing materials (picked up blocks to build base yesterday) and am considering using a Hebel panel instead of perlite mix as insulation layer of hearth.
I plan to use bricks on edges as oven base, as mentioned somewhere in Russell's book. Will follow your progress with interest.
Steve

[maver]

brick count

I built my 42" oven with a low dome (18" rather than 21") but had about 50 bricks left over beyond the 280 called for with the hearth and dome. Your usage may vary. I did cut all of my bricks into trapezoidal shapes above the fourth row.
The fornobravo plans call for the hearth bricks to be laid flat, which is what I did. The principle followed by the designers is to have a low enough thermal mass to be able to saturate the oven with heat for pizza cooking fairly quickly for home use - about an hour heat up time. If you are making it primarily for bread and anticipate needing to bake more than a few batches at a time then maybe you want more mass. I baked six loaves last week with 2 batches and had no problems, oven temp dropped from 550 to 475 over about 1 hour.

[Hendo]

Sourcing materials

I am still sourcing materials (picked up blocks to build base yesterday) and am considering using a Hebel panel instead of perlite mix as insulation layer of hearth.
I plan to use bricks on edges as oven base, as mentioned somewhere in Russell's book. Will follow your progress with interest.
Steve

Steve ? yes, sourcing materials in Australia can be a little challenging ? eg no manufacturers of (proper) fire bricks here in Adelaide that I can find. But there is one in Bacchus Marsh (Vic) which has distributors in the major capital cities I believe. Not so lucky with the Insulfrax Blanket, which I must buy direct from Melbourne!

I plan to follow a lot of good advice from fellow forum members, and insulate as much as possible. I will start with a concrete block base, 4? reinforced concrete on top with 4? perlite or perhaps a thermal panel like you?re proposing. There will be a brick veneer built around the perimeter to match the existing house bricks. The hearth will be around 1200mm (48?) above floor level, with a 900mm (36?) high work bench with sink, barbecue etc on either side. Just getting this far will be a major feat, so I don?t want to get too far ahead of myself right now. But I have allowed for a good sized smoke chamber and (masonry) flue, similar to that of Drake Remoray?s oven.

At this stage, I am allowing for an ash slot with a pit below it, but take the point other members have made that it could end up a waste of time when using the oven. I can easily change my mind after the base is completed - a bit more difficult the other way around though!

[Hendo]

Brick Quantities

Thanks Maver. I?ll start off with 280 bricks, and hopefully should have no trouble returning any excess! I?ve also read in one of your posts that it can take quite a while for your oven to cool to bread baking temperature after baking pizze, so probably bricks laid flat for the oven floor is the better way to go. I certainly don?t want to wait longer than necessary to get started cooking, and I think that bread baking will be less of a priority when using the oven. Having said that though, surely the extra inch of hearth (for bricks laid on edge) wouldn?t extend the overall heat-up time too much?

[james]

Hendo,
Let us know how your brick count comes out. That will be helpful to other builders.

You can definitely lay your floor bricks flat -- not on their edge. That will give you a cooking floor that will heat up fast -- and more importantly, stay hot after you have fired it, and it will do an excellent job of baking as well.
James

[maver]

As far as cooling to bread baking temperature I have since baked some baguettes of pain l'anciene at higher temperatures (about 650) after reading CanuckJim's description of higher heat baking of certain breads and found it worked just fine, plus allowed me to bake bread pretty quickly after raking out the coals .

As far as returning firebricks, it's certainly something you may be able to do, but remember they are quite heavy (not for one, but when you start moving a lot of them it becomes somewhat daunting) and they have crisp corners that tend to chip if you are not careful (and care fades when moving a lot of these). Of course, you have to balance the chore of acquiring more if they are not locally available and you run out. I found another local brick oven builder who helped me unload my excess (thanks again, Jack - we are really enjoying the wine) which felt a lot better to me than bringing back useable but no longer pristine bricks to the brickyard.

[Hendo]

Fire bricks and hearth height

James,
Thanks for your input ? I will certainly let members know the outcome re brick numbers.

maver,
Point taken about damaging the bricks ? having no experience moving other than clay bricks, I was not aware this might be a problem - thanks. The bricks I?m planning on using are 23% alumina 73% silica, which the manufacturer classifies as ?medium duty? and the most popular choice for brick ovens. The only other one I was considering has a 33% alumina 63% silica mix and is classified as ?high duty?. The Brick Primer recommends around 30% alumina and 50% silica, so I hope the 23/73 ones will be OK. The company also markets a premixed air-setting medium duty refractory mortar with a 22% alumina and 72% silica content, so I assume that this would marry well with the 23/73 bricks. Members views would be much appreciated on these matters.

On the question of the height of the oven hearth above floor level, I?d also appreciate members experiences. I?m around 6 ft tall, and thought that 48? high would be a convenient height. I was influenced in my decision by ovens seen during various trips to Italy, including the one posted here (hopefully) which is in 'La Focaccia' pizzeria near Piazza Navona. Taking my height and the (assumed 36?) workbench height as a guide, it appears the oven hearth is about 48? high. As you can see, I would still have to bend down a bit to see into the back of the oven. Note also the fire grate, which seems like a practical idea to me, and the shape of the door ?frame?, which is like the FB Ristorante Series. Not obvious from the photo is a vent/smoke chamber which has a conical shape ? the front face of the oven wall bends out in an arc like a protruding canopy (the other guy's right hand is pointing at it).

I?m also posting a couple of photos of a very old brick oven in a villa near Ulignano in Tuscany, which is around 6 feet in diameter, and has obviously seen some movement over the centuries. The owner told me that it had last been used to cook a meal for around 50 guests! Please excuse the mess in the room - I had to remove half its contents as it was to get to the oven door to photograph the inside of the oven, which appears to contain the beginnings of the next firing ....

[james]

Hendo,

Nice photos. Thanks. I like the Rome oven. I can't tell if it is site builder or a producer oven, but I can definitely see the oven opening pattern.

One your bricks, I have heard many times that 30% alumina is what you are shooting for -- and that includes our precast ovens and the bricks used in the Forno Bravo Artigiano ovens. I am wondering if there is a cultural translation going on with low, medium and high duty. My experience is that high duty brick are very high in alumina and are made for industrial purposes, such as kilns and furnaces. We are making food, not steel. I would check a little further, and go for higher duty bricks if you have to.

Would others agree with that?

On the Ulignano oven, I am sitting about 3 miles from that oven as I write. It's a small world. That's an oven that has seen a few meals.
James

[carioca]

Down Under firebrick sources

Hi Hendo,

I wonder if you have checked out Darley Refractories in Bacchus Marsh, Vic, who sell a "kit" of pre-cut (tapered) firebricks that I have got a quote for. Their tollfree number is 1800 453 880, talk to Tonia Taylor or Sue. They can e-mail you a file listing their "kit" materials, as well as accessories and other straight types of fire bricks.

I've ordered about a dozen or so more bricks than they say I'd need for a 39in dome, just in case I mess up...

In my case, the cost of railing the pallet to my nearest railhead is between 360 and 470 dollars! But I'm still at the preliminaries (designing foundations)...

BTW, the "kit" does NOT rpt NOT include the Insulfrax blanket, which I would have them add to the "kit".

If you wish I could e-mail you their docs...

Cheers,

carioca

[maver]

Oven height

I think you want to pick your oven hearth height based on the level that would be comfortable to slide pizza in and out of the oven - keep in mind that to slide it in you want the peel tilted up at an angle to allow the pizza to slip off. I think this generally gives you a lower oven than what might be comfortable to look into.

You certainly can err on the side of too high - worse case you build a raised platform at the oven entrance to allow easier work in the oven. Hard to correct too low.

[carioca]

re brick count

Hello again, Hendo!

I've counted 21 firebricks of the 230 mm x 115 mm size (tapered across the length 75 mm down to 63 mm) for the first course - laid flat - in my first rough sketch of my planned 1000mm dia dome oven (39in) (see attached).

This seems to tally with the quantities listed in the corresponding "kit" from Darley Refractories I mentioned before: 67 bricks of the 75->63mm taper; 33 of the 75->57mm taper and 25 of the 230 x 230 x 35mm (or 50mm) bricks for the floor.

For the 1200 mm dia. oven the "kit" specifies 100 of the first type and 20 of the steeper taper bricks, as well as 36 base tiles.

Note that the suppliers told me the first course bricks remain whole, but subsequent courses are built from bricks split in half across the 230 mm length.

Note further that the "kit" does NOT rpt NOT include any instructions (as I've already mentioned in other posts) - that's why I refer to it as the "kit" :-)

The sketch attached also shows the concrete blocks (400 x 200 x 200 mm) along the axes of a hexagon that are to support the circular hearth of about 1750 mm dia. ; the blocks are in turn to be supported on a concrete post&beam foundation that I' am still trying to suss out :-)

(You'll see that I need to readjust the two radials next to the oven opening so that they don't obstruct the cook's movements...)

Cheers and good luck, mate!

Carioca


IMPORTANT PS: Hendo, I stupidly mixed up diameter and radius in my measurements! So I sketched a 2m diameter oven, instead of a 1m diameter oven... of course the brick counts are totally OFF target! Will redo ASAP and advise new brick countshttp://www.fornobravo.com/forum/images/icons/icon11.gif
Red face

[DrakeRemoray]

The company also markets a premixed air-setting medium duty refractory mortar with a 22% alumina and 72% silica content, so I assume that this would marry well with the 23/73 bricks. Members views would be much appreciated on these matters.

I don't think you want to use an air-set mortar. I understand that they are not waterproof and therefore not ideal for outdoor use...

Drake

[Hendo]

Bricks etc

Hendo,
One your bricks, I have heard many times that 30% alumina is what you are shooting for -- and that includes our precast ovens and the bricks used in the Forno Bravo Artigiano ovens. I am wondering if there is a cultural translation going on with low, medium and high duty.
James

James,
Definitely a cultural phenomenon I'd reckon. As I mentioned previously, the company does do a 33% alumina 63% silica fire brick, but the tapered ones included in their 'kits' are of the 23/73 mix. So I guess my choice is either to go for standard shaped bricks with higher alumina content, or the lower ones that come tapered. While the tapered ones sound appealing, I'd want to be sure that the degree of taper is not too severe - otherwise I may end up with gaps on the inside of the dome. I hope to inspect some locally, so I'll be able to see this for myself. Of course, I could simply change the design to a smaller diameter dome, too, to suit the bricks.

[Hendo]

Hendo,
On the Ulignano oven, I am sitting about 3 miles from that oven as I write. It's a small world. That's an oven that has seen a few meals.
James

James,
Indeed it is a small world! Il Mattone is the name of the agriturismo where we stayed ? see pics. You?ve probably driven past. That view of San Gimignano in the distance is hard to beat!