In truth, whether refining elixirs or artifacts, the first step was to remove impurities from the materials. Only the methods and terminology differed.
Before long, the small golden cauldron grew hotter, its bottom already glowing red. Xu Qingtong tossed the black iron into it and watched with his divine sense as it slowly melted, beginning the smelting process.
As time passed, the impurities in the black iron gradually turned into wisps of blue smoke, while the black iron itself became dazzling molten iron.
Once the black iron stopped giving off blue smoke, the smelting process was complete. Smelting actually required considerable skill. Different materials contained different impurities; some were easily removed, while others were very difficult to eliminate.
For example, the impurities in black iron stone all had low melting points. Before the black iron could even melt into molten iron, those impurities would already have turned into blue smoke.
Some higher-grade materials, however, were extremely difficult to smelt. The gengjin stone Xu Qingtong had previously used to refine the Sinew-Building Elixir, for instance, had been very difficult to purify. The main material had a low melting point, while the impurities had high melting points. Before the impurities could vaporize, the main material would turn into blue smoke and vanish!
In such cases, he could only use the Filtration Method: first melt the main material, then filter out the impurities, and finally heat the impurities separately until they vaporized. This operation required the refiner to possess powerful divine sense as well as a finely honed Fire-Control Technique.
Neither requirement, however, posed much difficulty for Xu Qingtong.
He controlled the flames, gradually lowering the temperature inside the cauldron. As he watched the freely flowing molten iron slowly thicken, he mobilized his powerful divine sense and began shaping it according to the