They are often manufactured in larger sizes than pressed batts; these tend to be used by industries like the glass business. Variations with thinner walls are readily available. Glazes will soak into your porous surface of a silicon carbide shelf. I've generally place kiln clean on them in common stoneware https://squarebeams16036.dreamyblogs.com/29575847/rumored-buzz-on-silicon-carbide-mosfet-advanteg-st-micro