"Why is your sword lying on the ground?"
"I'm sun-tanning the sword to make it darker."
"Why?"
"Good question, kid. What's the darkest thing you can think of?"
"Crows?"
"...Sure. What else?"
"Hm... Cooking pots!"
"Good. Keep going. What's underneath the cooking pot?"
"Fire!"
"And where does the fire come from?"
The girl thought for a bit.
"Coal! Coal is the darkest thing of all!"
"That's right! Coal, or carbon, is what makes iron stronger. But I figure I can just darken the sword by tanning it instead."
With that, he flipped the sword to the other side.