Aspen substrate question

Can you mist aspen? I really like the texture, and how well aspen maintains accurate heating temps. The only issue is how dry this substrate can be.

Yes you can, but keep an eye on it as it can mold if it is kept too wet.

What heat source are you using? (heat lamp, ceremic heat emitter, heating pad, something else?)

A light misting should be fine, as long as the substrate isn't damp for days on end it shouldn't mold.