The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Allen Scott v. Pompeii-style

Gadjowheaty's picture
Gadjowheaty

Allen Scott v. Pompeii-style

Hello,

 

I've been trying to buy the Scott plans but no luck getting in touch with his son, Nick.  I'm not an experienced mason so a bit tetchy on relying solely on The Bread Builders to build a Scott-style oven.

Forno kindly furnishes plans for a round, Pompeii-style oven.  I seem to recall reading somewhere from Mr. Scott that the round style, while good for pizza, is not great for hearth bread.  Cannot recall why.  Dead spaces?  Too much retained heat by the geometry in the hearth firebrick?

Interested to hear from anyone their thoughts, or if having built a Pompeii oven, their experiences with hearth breads.  Many thanks.

idaveindy's picture
idaveindy

On a previous thread, you gave a link to a file on www.heatkit.com

I browsed around there and spent waaay too much time on this page   http://heatkit.com/html/bakeoven.htm

There are just so many designs, it's mind-boggling.

There is probably a Facebook group, or a Google-groups (or whatever they now call the old Usenet thing) for diy brick ovens.

This guy is a pizza pro: www.brickovenbaker.com  who became a reseller of pizza supplies and accessories.  He can probably point you in the right direction for a discussion group/forum for backyard brick wood fired or gas fired ovens.

--

From a beginner DIY point of view, the less curves in the construction, the easier.  I understand that the inner dome needs to be curved in one dimension in order to get the suspension of an arch.  But the footprint of the hearth and the base of the dome, can be rectangular.  

I've seen a time lapse video on youtube about building a round footprint, ie globe/sphere style dome.  It's do-able, but a lot more complicated, than one where the front, back and side walls are rectangular and vertical, and the dome is a cylinder as opposed to a globe/sphere.

I'm no expert, but my understanding is that the Pompei style is a spherical dome. Is that correct?  If so, do you want to cut and fit bricks to a sphere, or cut and fit them to a cylinder?

albacore's picture
albacore

Forno Bravo and UK Wood-Fired Oven in the UK are the goto forums for those wanting to build their own WFO.

Modular ovens (usually in the Pompeii/hemispherical shape) are also an option worth considering, where the oven is assembled from precast refractory sections. This makes for a much quicker construction.

I get the impression that Alan Scott ovens are literally massive constructions with a very thick hearth; fine if you are planning to bake bread in them every day, but possibly wasteful of fuel if you are only using them occasionally.

Lance

Gadjowheaty's picture
Gadjowheaty

Thank you both.  Idaveindy, yep, you're right.  Makes perfect sense.  Things of beauty to watch in stages, until I realized I'd be the one turning a sphere into a Salvador Dali.  Problem settled there, thank you.

Albacore, I'm trying to preserve dough (I mean, $) while learning as much as I can, so probably want to try as much as possible to keep it simple, but from the ground up.  I intend to scrounge a good deal and see what I come up with.  The BB calls for a hearth slab of min. 3 1/2" thick on top of a 6:1 portland cement/vermiculite mix of at least 2", so 5 1/2".  I think that's correct.  That's minimum, for infrequent use.  I live in a cold climate so would want to splurge everywhere, I think, on insulation.  I know nothing about any of this.  Is the firebrick+hearth slab (3/5") + insulating concrete slab (2") considered quite a bit, and inefficient in terms of wood use?

Thanks again.

MichaelLily's picture
MichaelLily

I built a Pompeii oven with the forno bravo plans 10 years ago with my dad. It is a 43” diameter floor and a max height of 21”. We used ceramic fiber board for insulation and ceramic fiber blanket for the dome. We added an inch or 2 of refractory mortar on top of the firebrick to add thermal mass. We used it very frequently for the first 5 years and less frequently since. We live in northern MN so it gets a lot of freeze-thaw cycles. We have used it in the dead of January and every season otherwise. I found it great for bread. In fact, I baked somewhere in the low thousands, maybe 2000 loaves in that oven, along with maybe 1000+ pizzas and hundreds of pounds of meat. It is as impressive today as it was 10 years ago.

 

I have also used an Alan Scott oven and to be honest, I liked mine better. But I only used the Scott oven twice.

 

The Scott oven plans look very simple, and the forno bravo plans are missing some information, but my dad and I were able to figure it out. Neither of us had done brick masonry before. In our area, and in 2011, materials for a functional oven of that size, plus tools we didn’t have, were about $2800. We spent more on a stylish stone facade, limestone countertop around the oven, and some other things. We used all firebrick, and 12” firebrick tiles for the hearth.

 

My advice is to build a big oven, because the extra space is nice.

Gadjowheaty's picture
Gadjowheaty

Thanks for the info, Michael.  I'm almost exclusively interested in baking hearth breads, though do want to throw the occasional pizza party.  I can't recall why, but in the Bread Builders, I think it was, they talk of the Pompeii/Tuscan style oven as better fitting flatbreads like pizza over hearth breads.  Outside of the difference in keeping live fire going for the pizza bakes, is there some reason the Pompeii oven would be seen better suited to flatbreads, and the scott-style oven, hearth breads?  Obviously, that doesn't imply in your case as you've used it to do everything. 

On the idea of larger capacity, if it's anything like cheesemaking (I make French alpine cheeses, in the gruyere and tomme families), it's best to pack the cave as a sort of homeostatic monitor.  Reading the recommendation that a full oven is better than an oven more empty, I think I get the logic.  Any thoughts here, re: building a bigger oven, as you mention?

MichaelLily's picture
MichaelLily

Here is my observation on how brick ovens work: the bricks get really hot and they stay hot, and so the oven chamber is hot, and that is how things bake.  The floorpan of an oven makes no difference to how well it bakes bread.  The round ovens are usually easier to cook in with a fire in the chamber because you push the fire to the side, which enables you to cook on one side and add logs to the fire on the other side.  In a Scott oven, the fire is in the back and you would cook in the front, which is not quite as easy.  The main difference is insulation and thermal mass.  Scott ovens have very thick hearths whereas, for example, my cooking hearth is 2".  A Scott oven would be able to retain enough heat to bake several more rounds than a lighter oven, or one with worse insulation.  I have baked 6 rounds of bread from one firing, though I usually would do 3-4.  A modular oven from a kit would do less; maybe 2, but that is a guess.

 

Here is the thing about oven size, from my opinion: you are going through a lot of effort to build a brick oven, whether big or small.  Heating the oven takes about the same effort and time for either size (most plans have a smallish oven plan and a bigger oven plan, and that is what I am referring to).  The charts telling you how many pizzas you can cook at a time?  Those are lies.  And a neapolitan pizza cooks as fast as you can prep them anyway, so it doesn't matter.  Our oven chamber is a 43" diameter hemisphere, and the charts say you can make like 12 pizzas at a time.  We make 2.  We can make 3 but there really isn't a point to it.  The charts don't take into account that the fire in the oven takes a lot of space, and I like to make 12-16" pizzas instead of 8" pizzas.  We can do 2 turkeys and a side at the same time for Thanksgiving.  And to answer your question more directly: a full oven load for me is 18 pounds of dough.  I've done 18 loaves in a load, and I've done 2 loaves in a load.  They came out the same. I also made an 8 lb loaf because my opening is 19" and I figured I could fit the dough in and get it out.  That also came out great.

 

To summarize, I have found a lot of uses for the big space, and I like it a lot.  It does any size well and gives you a little more freedom: more space to use if you want, good results all the same.

Gadjowheaty's picture
Gadjowheaty

Thanks Michael.  A few questions.

You mention that in a Scott oven, the fire is in the back, and you cook in the front.   It's not clear to me - the Scott ovens cook with retained heat only, so the ashes/embers are cleared out, the floor is mopped clean and the oven hearth is now open.  Also, as I understand it (and I am very new, so please forgive any redundancies you're already covering, if I've not heard them), the door is closed and the period is given to equalize the oven temp (and lower that temp to baking range).  So, an empty, hot chamber with heat ideally distributed around equally.  The reason for the heavy insulation - retained heat only.  Is this what you were saying?

On the large oven - trust me, I love going large.  The brewing system I built is 20 gallons.  Exactly the same logic as you're talking about - just as much effort to brew 5 gallons as 20.  I have a lot of friends, especially around festival time. :)

What I wonder about bread, however, is the need for steam.  A loaded oven with the door shut is something like a cloche, it seems to me - no?  On the other hand, I can see just using a garden sprayer or something like that, or a pan with lava rocks, etc.  It would be nice to have the capacity.  Any thoughts on the steaming aspect?

So, almost exclusively, I would like to cook hearth breads, with the possibility of increasing loads or multiple bakes over time.  Occasionally, for pizza parties or just home consumption, flat breads incl. pizzas, with fire left inside.

So, a thicker insulation for the bread needs.  A larger chamber possibly, allowing for increased capacity - no desire to build a second oven, as you seem to be saying.  I hear the logic of my noob masonry and the difficulty of a sphere v. a half-barrel design.  I have to admit, too, I just prefer the Scott style, personal taste, I guess.  That said, I'd like to bake pizzas from time to time. 

The larger Scott styles - work well?

MichaelLily's picture
MichaelLily

Cool brewing system! It looks like a blast.

 

You are correct.  Here is an example of what an oven weekend looks like for us when we maximize productivity:

Thursday: make pizza dough

Thursday afternoon or Friday morning: light a big fire

Friday: re-light the fire in the afternoon, or keep it going all day, or at least 5 hours, if we started that morning. Make bread dough.

Friday night: reduce fire to a cooking fire.  Hearth surface temperature should read 700-725F (this number is subject to what material your hearth is, and also its thickness). Cook pizzas.  Close door for the night (keep fire inside).

Saturday morning, or several hours before baking: open oven, sweep out coals and ashes. Oven temperature measures 600-650. Replace door.

Saturday afternoon: When temperature cools to 500, bake first load of bread.  Bake time for my bread is approximately 22 minutes.  Replace door and wait a half hour.  Temperature should be about 450.  Repeat process for second load.  A partial load will not cool the oven as much, and my loaves are baked straight from the fridge. After baking, close the door for the night.

Sunday morning: Oven temperature approximately 325 hearth, 350 ceiling.  Prepare pork butt, brisket, or ribs (or all of them!).  Bake on a roaster until the desired temperature is reached, with the door closed.

 

This is our super schedule, and you get a lot of food from one firing.  Some foods you cook with a fire in the oven.  My dad loves to roast coffee (he got essentially a raffle drum on a rod that he attaches to his drill so he can rotisserie the beans). We also really like chicken wings (raw, straight from frozen) and butterflied shrimp.  These are all great because we are heating the oven anyway.  In a Pompeii oven, you start the fire in the middle, and then move the fire to one side, and then the other side (or in the middle, and then kind of all over, and then on one side).  In a barrel vault oven, you start the fire in the front, and then move it back.  This is only relevant for the times you want to cook while there is a fire in the chamber.  Trust me, it is fun to cook during all stages of oven heating and cooling.  Cooking with the live fire is more interactive.

 

Regarding your insulation question: yes.  Your oven floor, walls, and ceiling will lose heat in every direction, which amounts to two options: inside the oven chamber, and outside the oven chamber.  Ceramic fiber board and ceramic fiber blanket do such a good job at insulating, that it effectively blocks the heat from being released outside the oven chamber, so the retained heat in the bricks is being released only into the oven chamber (and into the food, and some out the door).  

 

Regarding steam: I have used a garden sprayer, but I think I stopped using it.  Make sure your door closes off access to the chimney, and then your chamber is not vented and there is no need for steam.  This is good for breads, and it makes meat wonderfully moist (and meat seems to cook faster).  Your cloche analogy is accurate.  You could use a home oven type steaming setup if you want, but I don't think it is necessary.

 

Regarding spheres: we used what the Forno Bravo plans call "the Indispensable Tool."  We used an office chair wheel (one on a swivel), removed the wheel, drilled a hole through pipe, replaced the wheel with the pipe, and attached an elbow bracket on top, to which we attached some scrap wood to make a kind of seat for each brick to sit on.  We centered the wheel on the oven floor, attached it to plywood and braced it in place, and then the tool would swivel, pivot, and spin anywhere we wanted, with the seat always 21" from the center of the hearth. We did not have to take any other measurements.  I will say that building a square door into a hemisphere was not particularly easy, though.

 

If you decide to build a barrel vault oven, they seem pretty straightforward.  My recommendation is to skip the vermiculite/perlite insulating layer and floating slab setup, and to instead use 2 or 3 inches of ceramic fiberboard.  I don't recall how thick the hearth is in the plans, but, if I recall correctly, if a firebrick is 2.5"x4.5"x9", then I wouldn't go any thicker than 4" for the hearth.  You can plan on some shifting of bricks in your oven over time and heating cycles, so I ordered 12x12x2.5" firebrick tiles for ease of use.  

 

With modern insulation, I think 4" for the hearth and 6-8" on the walls and ceiling would be more than enough mass.

Gadjowheaty's picture
Gadjowheaty

Hey Michael - I just posted elsewhere and realized I spaced replying earlier.  Sorry - very considerate of you to post such a wealth of information.  You've given a ton to consider - thank you.

You are ingenious, obviously, I am not.  The welding setup, you'll note, I'm not giving you any closeups of the welding, ahem.  Your chair jig is awesome.

The floating slab, you mention don't bother.  I thought the slab was there to help remediate against heat cycling issues, yes?

MichaelLily's picture
MichaelLily

I thought the floating slab was there to prevent heat loss into the foundation (block walls). With CF insulation I don’t think it matters. Whichever is easier is what I recommend, or if you think there is a possibility you might move it somewhere else, the floating slab makes that somewhat more viable.

Gadjowheaty's picture
Gadjowheaty

Thanks, Michael.  I just checked the BB book and he says it's to give some flex with temp changes, and yep, as you say, also to make it easier to move the oven if you need to. 

Thanks too for the info on the CF materials.  New to me, seems hands down a better choice.

 

albacore's picture
albacore

Don't skimp on insulation - you will come to regret it. Also, make use of modern materials; for example, insulators like calcium silicate board (rigid) and ceramic fibre blanket (flexible) are much better performers than vermiculite concrete (vermicrete).

At least in the UK, a typical pompeii build might be a raised base (often cast concrete), then 3" calcium silicate board, then your firebrick floor. You can play the tune with firebrick thickness and orientation to get the thermal mass you want. Then the dome is built using cut firebricks, though some builders use red bricks to economise. Then 2 - 3" ceramic fibre blanket, then a 2" vermicrete shell to give some rigidity and a render (stucco) finish.

Also bear in mind that a big oven may sound attractive, but it will take longer to heat up and use more fuel than a smaller one, so carefully size up what you really need. If your oven takes all day to heat up, it will put you off using it, as well as being wasteful of natural resources.

Lance

Gadjowheaty's picture
Gadjowheaty

Excellent.  Thanks very much, Lance.  I know nothing about the modern insulation materials you mention (brand new to all of this, The Bread Builders my first and nearly only exposure, so far), so thanks on these, too.  Will do some digging.