Superheat Item is a magicspell that becomes available at level 43. Superheat item allows you to smelt one bar without the use of a furnace. Superheat item costs 4 Fire-Runes and 1 Nature-Rune.
Smelting iron ore with Superheat item will always succeed.
Note: Superheat item does not work with Gauntlets of goldsmithing. The spell can be used to turn Gold ores into Gold bars, but the caster won't receive the bonus experience usually associated with smelting gold bars with the gauntlets.