i have colored a lot of parts, i have always sealed the lid with furnace sealant,i put a piece of paper to burn and use up oxygen i put charcoal in and add bone charcoal and layer it,i ran air to have constant bubbles to break up the steam envelope.i ran my kiln at 1200 and depending what i had in my crucibles allowed time to get everything up to temperature. when i quenched i pulled the pack out knocked the lid off and dumped it into the tank.if you made you charcoal and its wet it will get scale.or if you dont cook the bone charcoal enough. that's all i got. mc