Greenfield
Adventurer
Solid Fog stops arrows, I would say it is a physical barrier and would stop the bead. The explosion afik would radiate normally into the fog 20 feet and 20 feet outside.
Mind if I ask why the explosion would penetrate when the bead wouldn't?
To reiterate my own previous thoughts: Fireball exerts "very little physical force". If it exerted *no* physical force I'd agree that as a pure energy type it could penetrate. But that's not the case. It exerts some small measure of physical force, which means it's a physical phenomenon to some degree.
The gas cloud expansion is blocked by barriers, and has to plot it's distance around them. Solid Fog acts like such a barrier.