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Using ADVANCER® Shelves in Wood Fired Kilns

ADVANCER® shelves have been used successfully in many wood-fired kilns. However, they should not be used in areas where there will be direct flame impingement early in the firing, such as fire mouths and areas adjacent to checker walls in second chambers. In these areas a conventional, thicker silicon carbide is preferred due to their ability to better withstand thermal shock. Wadding on brick posts under ADVANCER shelves is also recommended to minimize surface contact areas with massive kiln furniture.

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What Would Cause an ADVANCER® Shelf to Crack During Firing?

The vast majority of failures with ADVANCER® shelves can be traced to uneven temperatures across the shelf (thermal gradients) causing thermal shock and shelf failure. This can occur on heat-up or on cool-down for a variety of reasons. Typical problem areas in kilns include the bottom layer of shelves in a car kiln, where the seal between car and kiln is not tight permitting cold air to rush in when the kiln is shut off, using posts that are too massive (see “Do I need special posts for use with ADVANCER shelves?”), direct flame impingement on shelves early in the firing, overly large sight ports permitting cold air to cool off shelf areas unevenly, shelves too close to damper areas causing uneven cool-down of shelves in close proximity to damper. If you have any concerns regarding the use of ADVANCER shelves in your kiln, please call to discuss your particular situation to make sure that ADVANCER is right for you!

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Why do ADVANCER® Shelves Cost More Than Other Shelves?

ADVANCER® shelves are a nearly handmade product. Composed of an advanced nitride-bonded silicon carbide formula, each shelf is slip cast in a series of custom molds with all corners and edges rounded to produce smooth surfaces for ease of handling. ADVANCER® shelves are dried slowly and carefully to remain flat. Once the shelves are dry, they are fired not once but twice in excess of 2500° F. All other shelves whether cordierite or conventional silicon carbide, are ram pressed and single fired. Unlike cordierite shelves ADVANCER® will not warp and at only 5/16” thick, they allow for more stacking space and reduced energy costs.

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Can ADVANCER® Shelves Explode if They Get Wet?

Due to the extremely low porosity (less than 1%) of ADVANCER® kiln shelves, it takes prolonged exposure to a direct and continuous moisture source such as rain, standing water from a floor or condensation to penetrate the shelf. Water is slow to get in, and once in it is slow to get out. Therefore a temperature controlled dry out schedule must be observed prior to taking the shelves to normal firing temperatures. Slow bisque firing is not adequate to insure complete moisture removal! If you know or suspect that your shelves have water in them, you must follow the dry-out schedule outlined in the Saint-Gobain Technical Bulletin Warning “Storing and Drying Requirements for ADVANCER® Refractory Components.” If you are uncertain about moisture exposure problems with your shelves, please don’t hesitate to contact us!

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How are ADVANCER® Shelves Made in Comparison to Conventional Silicon Carbide Shelves?

Unlike conventional silicon carbide shelves that are made from a grainy, semi dry mix that is ram pressed into molds, ADVANCER® shelves are made from an extremely fine grained mix of silicon carbide that is slip cast into plaster molds and then high fired multiple times. The fine grained, tight structure of ADVANCER shelves is one of the key reasons why they stay flat and can be manufactured in thin cross sections with exceptional strength. All corners and edges are rounded to produce smooth surfaces for ease of handling and strength.

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Using ADVANCER® Shelves in Soda Kilns

ADVANCER® is often used in soda kilns. Clean-up of soda drips from the surface of the shelf is a breeze since the low porosity of ADVANCER does not allow the soda glass to get much of a grip on the shelf. Spraying or dumping soda into the kiln firebox and having it naturally disperse throughout the kiln is the preferred method of introducing soda into the kiln. Soda can also be introduced in a dry form when combined with whiting, with good results. We do not recommend spraying liquid soda solutions directly onto ADVANCER® shelves through a port hole, since this practice may lower the temperature enough to the point of soda contact to cause a significant temperature gradient across the shelf leading to cracking, thermal shock and failure.

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Are ADVANCER® Shelves Safe for Electric Kilns?

Yes! Although some forms of silicon carbide are known to conduct electricity, ADVANCER® is a relatively poor conductor of electricity due to the oxide glass layer present on all ADVANCER shelves. Be sure to select the correct size shelf for your kiln and make sure your kiln is in good repair with no elements hanging out of the grooves where they can sprawl out onto shelves. Finally use common sense and never reach into an energized electric kiln!

Important Information on Firing with ADVANCER® in Resistance Coil Element Kilns.