Disclosed herein are methods for bonding refractory substrates, such as zircon substrates, without the use of a bonding agent. Exemplary methods include (a) providing a plurality of refractory components, each component having at least one surface to be bonded, (b) polishing each surface to be bonded to a surface roughness (Ra) of 200 nm or finer, (c) contacting the surfaces to be bonded to form an unbonded refractory substrate, (d) firing the unbonded refractory substrate, and (e) subjecting the surfaces to be bonded to a compressive force during firing. Methods for making refractory forming bodies are also disclosed herein.