How big the bellows? How big the air opening(s) in the bottom of the forge? How deep was the charcoal pile? how far up from the bottom was the "hot spot" and about a dozen more questions *you* need to answer to get anything more than a wild guess.
Example: I have problems with my truck not going fast enough---can you trouble shoot it from that much info? (would telling you it was 20 years old, 4 cylinder, gas engine, and carrying a heavy load help any?)