I have noticed, and cannot find information of this anywhere on the site, that if you are using the Edgeville Furnace to smelt iron with a Ring of Forging, the special effect that lets you smelt 2 bars at the same time only uses 1 charge of the ring! I don't know what the actual statistics of it are, but over a short period of time, it seemed to average out to about 10 extra bars per ring. This means that you get, I guess, about 150 charges per ring instead of 140. BONUS!