No loss and terrific smithing exp with this method at the Blast Furnace. Smith gold bars and runite bars at the same time to even out the costs. This way, it is the fastest way to 99 smithing without wasting a single gp. You will need a coal bag for this method which can be obtained through motherlode mine.
Gp and Exp rates one kind of bar only:
Iron bars: 120K/Hr and 75K Exp/Hr
Steel bars: 900K/Hr and 94K Exp/Hr
Gold bars: -1M/Hr and 337K Exp/Hr (135K Exp/Hr without goldsmith gauntlets)
Mithril bars: 560K/Hr and 108K Exp/Hr
Adamantite bars: 950K/Hr and 101K Exp/Hr
Runite bars: 1,2M/Hr and 107K Exp/Hr
Music: High Seas (Trap Remix) - OSRS Beatz