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What is crazing?


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Philpom I know that you know what crazing is and what causes it. I do agree that is looks beautiful and do not know much about how much it diminishes the life of something that lives outdoors. My hunch is not much-if at all.

That is the genius of the Kamado Kamado in that they have flexible grout between tiles-- that are also set in flexible grout. That flexibility allows for the difference in the expansion rate between the main Kamado and its finish.

The crazing is basically the glaze breaking into irregular tiles as the unit heats and expands because the ceramic unit and the glaze expand at. slightly different rates causing the glaze to crack to accommodate the expansion.

It is my understanding that Grill Dome does not have this problem because the paint they use is flexible.

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Some claim their cookers sweat through the crazing. I would have thought that in freezing temps that could damage the cooker but it has not that I have ever heard. I have seen pictures of BGE'S and Primo's uncovered and covered with snow and they are fine so I don't see there is really any harm done as a result of crazing.

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what is Crazing?

In generic terms a rigid finish is applied to a rigid base but they both expand and contract at different rates so after X number of heating and cooling cycles the crazing appears - it's a relief or fracture in the finish.

This is why for example when they put large sections of cement down they include expansion cracks - to allow the cement to expand and contract - or when you put a deck down you leave a small space between the deck wood - so when it expands it doesn't press against the board next to it.

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If you research crazing in the business of ceramic pottery, it is pretty much classified by them as a defect in the glazing process. Make no mistake, most officials in the kamado world claim it is a naturally occurring process. Even ceramic pottery experts admit that unless you are eating on the surface of the crazed ceramic, it poses no problem or limitation. The only company I know of that claims likewise, and is on record of honoring their warranty to replace a kamado grill that had crazing, to my knowledge, is Vision

More about crazing:

http://glassandpotterysellers.org/glossary.html

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  • 1 month later...

This was posted on the Primo forum by King-O-Coals in response to someone asking if they should keep their unit that had crazing out of the box. I was surprised that they said Primo was willing to replace the unit.

If you think the crazing will make you crazy, get an electron microscope and check out the fibrils spanning the gaps between crazings. Also, if you get one without crazing, be careful with it. It will be potentially weaker than a nicely crazed piece.

Crazing occurs in polymers, because the material is held together by a combination of weaker Van der Waals forces and stronger covalent bonds. Sufficient local stress overcomes the Van der Waals force. Once the slack is taken out of backbone chain, covalent bonds holding the chain together hinder further widening of the gap. The gaps in a craze are microscopic in size. Crazes can be seen because light reflects off the surfaces of the gaps. The gaps are bridged by fine filament called fibrils, which are molecules of the stretched backbone chain. The fibrils are only a few nanometers in diameter, and cannot be seen with a light microscope, but are visible with an electron microscope.

A craze is different from a crack in that it cannot be felt on the surface and it can continue to support a load. Furthermore, the process of craze growth prior to cracking absorbs fracture energy and effectively increases the fracture toughness of a polymer. The initial energy absorption per square meter in a craze region has been found to be up to several hundred times that of the uncrazed region, but quickly decreases and levels off.

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That is all pretty interesting stuff.

I think as far as what Ross is talking about - crazing is a defect if it comes out of the oven that way. Not if it develops over time and during usage. My Primo was delivered craze free (as I think it should be) and the crazing developed over a period of time while I cooked with it.

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Maybe that is why Primo offered to replace it because it arrived that way and it is not supposed to. I saw one fairly recently at a place and it was crazed all over and had never been cooked on but so was the KJ I saw. I think the black color makes it stand out more too.

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Maybe that is why Primo offered to replace it because it arrived that way and it is not supposed to. I saw one fairly recently at a place and it was crazed all over and had never been cooked on but so was the KJ I saw. I think the black color makes it stand out more too.

I think you are right, the black color and bright sunlight will really bring it out!

"This product suffers from Crazing - a natural process that makes your kamado a unique and one of a kind piece of art."

Take a picture of your crazing and use it to identify your kamado should it every come up missing!

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Now there's a creative idea. Just like a fingerprint. My XL arrived w/ a tiny bit of crazing; I didn't give it a second thought. I've cooked on it 10x now, and don't see this becoming a cause for major concern. There is no flaking or compromise of the structural integrity of the glaze. If it becomes a problem, I have confidence in the Promo customer service folks.

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When I said crazing is a defect, that is a definition given by pottery people in the trade, and used more as an artistic term than to convey structural integrity. They will produce certain artifacts with intentional crazing, to create a web effect, but when crazing occurs on, say a fine ceramic serving plate, it is generally the result of something in the original recipe gone awry.

I do know that Vision is on record here on the Forum to have replaced a grill that had crazing.

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