Clearly, Tony is pondering bondage! Or, failing that, science. He probably wears much the same expression thinking about one as he does the other.

Nice, nice job on the muscles in his arms and torso. Like axolotl_lan, I love the loose way the string/rope/ribbon/bondage!tie is wrapped around Tony's wrists in the second picture (mmm... hands...).

this is for winhall for showing me this.

Oh God, I remember that. *snorts* Only in comics.