soon i plan to redo a gasket on my BGE, using Permatex gasket maker "ultra copper". measuring the parallel gap size between top & bottom without any gaskets.
make 3 spacers (or use screws with appropriate thicknes) and lay these spacers at about 3clk, 6clk & 9clk position on the cleaned edge. Pour a thick bead of the permatex all around, leaving spacers in place. Place wax paper over the permatex and close the lid overnight to allow to cure.
peel off the wax paper.
the next day, cut out the spacers & fill with permatex (using wax paper again) close the lid for another overnight curing time.
remove all wax paper & with a sharp blade cut off any excess cured permatex, to form a smooth edged gasket inside & outside. This will last a lifetime.
I tested a 600F teflon rtv version on a ceramic block and placed it inside the bge next to the coals & the dome temp read 400F - no change occured to the test piece and remained rubbery.
Here is the stats of the Permatex copper i intend to use:
Permatex® Ultra Copper® Maximum Temperature RTV Silicone Gasket Maker
OEM specified. Highest operating temperatures for 4-cylinder, turbocharged or high-performance engines. The most advanced, high temp RTV silicone gasket available. Sensor-safe, low odor, noncorrosive. Superior adhesion. Three times more oil resistant than conventional silicones; eight times more flexible than cut gaskets. Temperature range -75°F to 700°F (-59°C to 371°C) intermittent; resists auto and shop fluids and vibration.