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MAINEWOODHEAT 02-14-2007 10:29 AM

Le Panyol construction and Stability
A recent chat room exchange on the Forno Bravo site raised the question if anyone had any knowledge of le Panyol ovens. A correspondent named "redbricknick" in California offered the only reply which was the speculation that a number of le Panyol ovens had exploded in pizzarias on the East Coast in the eighties.
The Maine Wood Heat Co., Inc. has been building and promoting the construction of high efficiency wood fired masonry heaters, masonry cookstoves and masonry ovens for nearly thirty years. We are the author of several books and construction manuals on masonry heater, and cookstove and oven construction, including a construction manual for the le Panyol oven cores.
The le Panyol oven cores have been available in the States now for about seven years. The Maine Wood Heat Co. Inc. is the North American importer of the le Panyol ovens. The French parent company, Fayol, which manufactures the ovens has been making components for wood fired ovens since l840. The world's most famous bakeries in Paris use brick elements manufactured from the renowned Terre Blanche (white earth) that all of the le Panyol cores are made of. The Terre Blanche is an all natural organic deposit that is quarried, processed, formed, dried and fired in the wide variety of shapes that make up the le Panyol cores and other commercial bake oven brick shapes. It has the highest rating given by the French government for direct contact with food and is one of the only oven products in the world made with all natural, food safe ingredients.
As it happens, the same food safe fired Terre Blanche elements are also very friendly to fire. In the factory itself, the elements are not cold cast, dried and then shipped. They are formed, air dried and then kiln dried to a very high temperature so that they are a true fired earthenware product when they are shipped out. We routinely see fires in these ovens that bring the material to temperatures in excess of l000 degrees fahrenheit. In a typical burn cycle from a cold start, a domestic sized oven with l2 to l5 pounds of wood, can reach temperatures in excess of 900 degrees in 45 minutes. The fuel required to sustain 750 degree temperatures for pizza is very minimal. We once cooked 55 ten inch pizzas in an afternoon for the Masonry Heater Association annual gathering with a carefully weighed twenty two pounds of wood.
Elsewhere in the Forno Bravo literature on their web site, it is suggested that pizza ovens and bread ovens are two different species. It is true that most manufactured cold cast refractory cores are relatively thin walled and are more appropriate to live fire pizza style cooking than for stored heat bread baking. In the case of the Panyol oven cores, however, even the smallest domestic model with a two foot hearth, has a core wall thickness of 4.5 inches. This wall thickness, combined with sufficient insulation makes it very easy for the user to bake bread from stored heat after the fire is removed. At the same time, with live fire cooking, the semi-insulative, thick walled construction, allows for a full range of cooking at very high or very low temperatures with extremely modest amounts of wood. We recently spent an evening with friends where chicken, potatoes, squash, pies and bread were all cooked in the oven. Just before the meal started we also place six lamb chops directly on the hearth in the rear of the oven just in front of live coals. We turned the chops once and they were cooked to perfection in about five minutes. We then raked the coals over the spot where the chops had cooked and within another ten minutes the oven floor was completely s]clean and white again, ready for bread or any other hearth product.
The suggestion from "redbricknick" that Panyol ovens exploded, while false, both as to timing or event, raise an interesting question about what causes refractory materials to fail or in this case to explode. While in France I have visited bakeries that have had Terre Blanche floor tiles in continuous use for three generations. In the third generation,masons crawled into the oven and turned the dry laid tiles over giving the new bottom face a chance to face the fire.
You can break almost any refractory product easily with a hammer or a maul if you hit it with sufficient force or if you drop it from a height of a few feet. Terre Blanche is no exception to this rule. Similarly, while refractory products, by definition, are able to resist high temperatures, they cannot simultaneously handle high temperatures and large amounts of water. If we took any oven core on the market and heated it to 900 degrees inside, we could probably do a great deal of damage to any one of these cores by throwing buckets of cold water into the super heated oven. As water turns to steam it expands very rapidly. A little bit of water carefully and properly introduced into an oven is a standard practice in classic wood fired baking. A little bit of water creates a great deal of steam and this steam plus water in the bread dough forces the bread to swiftly expand in volume before the crust is formed from the oven heat. Just before the loaves are loaded into the oven, they are slashed with a razor to allow this rapid escape of water from within the dough and the controlled expansion of the dough into a classic elegant loaf shape. When preparing any oven for bread baking, it is customary to swab the deck with a wet mop. This cleans the fly ash off the surface without introducing enough water to cause any absorption of water into the material and any subsequent steam expansion within the material.
If one builds any kind of oven in an environment or climate where there is a lot of rain, it is necessary to cover the oven with a genuine roof, no matter how primitive or fancy the oven is. Once water gets into an oven core, the introduction of fire and a rapid rise in temperature will cause the water in the mass to heat up swiftly, change to steam and expand with destructive force, causing chips to fall off the inner surface of the oven core. Traditional clay and straw ovens of Quebec were always covered with a water proof roof because the climate has high humidity. Only in those climates, such as those of the very arid Southwest, were ovens traditionally built without a roof.
Whether we are dealing with freeze thaw cycles where water expands and causes damage, or steam and fire cycles where excess water cause thermal shock to refractory materials, water in large amounts and hot ovens never mix.
If an oven of any kind on the East Coast ever "exploded" it would almost certainly be the result of someone throwing water into a hot oven, versus any failure of the material or construction of the oven , no matter what the brand. I hope this information is useful to those who have raised the questions about le Panyol. We welcome further discussions and are happy to be a part of a rapidly expanding interest in wood fired ovens of all kinds in North America.

Sincerely yours,
Albert Barden
President, Maine Wood Heat Co. Inc.

jengineer 02-14-2007 07:49 PM

Re: Le Panyol construction and Stability
Now that is a very nice first post. Thanks for the enlightenment

dmun 02-15-2007 05:35 AM

Re: Le Panyol construction and Stability
Thanks for your thoughtful post. I have added a comment to the original thread linking it to your message, for the benefit of anyone googling around.

It's no fun selling a product that gets "urban legends" attached to it.

james 02-15-2007 06:04 AM

Re: Le Panyol construction and Stability
Hello Albert,
I know that we have exchanged emails in the past to say hello, and want to apologize that our group was poking fun at your products. We try to have a sense of humor, which may have gone overboard. La Panyol has been around for many years, and we all respect that.

Also, welcome to our group. We have invited other MHA members to join our Forum, and FB is in the process of joining the MHA, and we are very interested in hearing about your experiences and look forward to sharing what we have all learned.

CanuckJim 02-15-2007 06:15 AM

Re: Le Panyol construction and Stability

That was a very thoughtful and thorough message. I've never bought any of the "urban legend" stuff either. Maine Wood Heat and the MHA have been around a long time, and I've always valued the professional approach you guys take to building. It's odd how these things get started. I've been told many times that adding steam to my oven will make it blow up. Huh?

Then again, some people out there make their sourdough starters at midnight, black cat nearby, holding a special stone. Huh?

Personally, I think the more communication and collaboration we achieve, the better off we'll all be.


jwnorris 02-15-2007 07:38 AM

Re: Le Panyol construction and Stability

Originally Posted by CanuckJim (Post 8067)
<snip> ...holding a special stone. <snip>

You mean the stone I bought isn't special afterall?


CanuckJim 02-15-2007 07:47 AM

Re: Le Panyol construction and Stability

Maybe, maybe not. True special stones are gathered by Wicca followers near Stonehenge, on the Salisbury Plain, at the exact moment of the summer solistice. Otherwise, yer outta luck.


redbricknick 02-15-2007 01:04 PM

Re: Le Panyol construction and Stability
In lieu of the long winded and masterfully crafted series of excuses I usually run with after saying something stupid, I offer a heartfelt and modest apology. I'm sorry your enlightening and empathic post had to be born out of such an immature gesture on my behalf.

james 02-15-2007 01:22 PM

Re: Le Panyol construction and Stability
Did you hear that they have found a village near Stonehenge and uncovered a path between the village and the "special" stones? The scientists are pretty convinced that Stonehenge was a burial alter to honor the dead. Pretty nice way to go. So it wasn't a huge pizza oven after all. Darn.

Nick, I think you confused that oven with the drummer in Spinal Tap -- it just spontaneous combusted.

Rob BU 01-27-2009 11:05 AM

Re: Le Panyol construction and Stability
Indeed, this is a most enlightening exchange--and civilized too! Remarkable site this is.

It does seem that both the Le Panyol and Forno ovens are time tested quality products.
Doubtless there are many others.

I want to use both gas + wood. (Burning of wood is soon to be restricted in parts of California, and may be outlawed in some areas).It seems that a few oven makers have fancy controlled gas units (I suspect pricey, and more often used in commercial units, while other mfgs seem to suggest a simple pipe with holes, similar to the kind used in fire places. These would lack the auto-shut-off safety feature, are not thermosat regulated. Any experience here?

Rob BU

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