The "Z-Kit", a brief summary:

The z-kit (zircon kit) is a two part mixture comprised of a powder (milled zircon) and a liquid (colloidal silica). When they are mixed together, a slurry is formed which can be applied in the wet state using a brush. By painting this on a furnace or kiln, the underlying insulation material is protected with a highly refractory ceramic shell coating. This refractory wash is like white-wash, but good to 2500°F. This hard coating repells glass, and though it can be wet by moltin glass, it does repell the acid atack. So it makes a good wash around doors and other moving parts that can get sticky with drips of glass. It is also great for repairing ceramic items that are heated, like a cracked Giberson Ceramic Burner Head that needs a repair.

Here is how I repair a broken Giberson Head:

"I put the liquid (colloidal silica) in a plastic bowl and soak all the ceramic parts. While everything is wetting, I mix a couple of tablespoons of the powder (milled zircon) with some of the colloidal silica to make a slurry and I paint this slurry in and on the cracks as I put the parts together. At this stage everything is very wet. When you apply the slurry it flows by capillary action into the cracks.

At this point, carefully clean out the holes in the face of the burner with "q-tips" and set the head into a kiln at 200° F to dry for a couple of hours.

Let everything cool. Then, thoroughly wet the head again with the colloidal silica and proceed with an additional application of slurry into all remaining cracks and unwanted holes. If you have large holes in the sides of the burner and need filler material, crush up a soft brick and use it as "grog." This can be dusted onto the slurry or mixed with the slurry to make a filler-paste like substance. Put this into the bigger holes and let dry completely.

When using colloidal silica, always dry the repair project thoroughly between each application. It generally takes three applications to complete the repair. The difficult part comes with the patience required to clean out the original manufactured holes in the face after each treatment.