Clinker formation in cornburning stoves

I own a corn burning furnace. The unit heats my house efficiently and very cost effectly. The formation of these clinkers... hard porcelain-like stones within the combustion chamber are trouble-some, to say the least. These clinkers are hard as rocks when first removed from the burnpot. Set them overnight on a shelf...they turn to powder. Why do these clinkers form, why do they turn to powder when removed from their "element"? How to eliminate clinker formation?