Bricks required for a 43" oven
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.
Snap in Aust.
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.
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.
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!
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?
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.
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.
Fire bricks and hearth height
Thanks for your input – I will certainly let members know the outcome re brick numbers.
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 ....
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.
Down Under firebrick sources
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...
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