Have I forgotten how to sharpen weapons?

[Afterburner]

Found a functioning forge that didn't immediately disconnect me when I clicked on it.

Clicked on it, got some new-fangled tradeskill interface I've never seen before, and certainly not back in 1999. Eventually clicked on the "Experiment" button, which gave me the old-school tradeskill container interface. Into the container I put:

1x Rusty Weapon
1x Water Flask (store bought)
1x Sharpening Stone

I clicked "Combine", and was informed that those ingredients in that combination do not combine to make anything.

Am I doing something wrong? Or is this a bug?