When purchasing ceramic bisque (unglazed, once-fired pottery), the most critical factor is the firing temperature (Cone rating). You must ensure the bisque is compatible with your intended glazes, typically categorized as Low-fire (Cone 06-04), Mid-range (Cone 5-6), or High-fire (Cone 10). Additionally, verify the porosity levels; a high-quality bisque should have enough absorption to allow glaze to adhere evenly but be durable enough to survive shipping. Check for surface smoothness and the absence of 'pinholes' or 'bloating,' which indicate poor initial firing cycles.