Blasting Jelly (relevant):
This volatile gray paste sticks to solid surfaces and creates a concentrated blast when exposed to fire, making it a valuable excavation tool. You can apply 1 dose of blasting jelly to a 5-foot square as a standard action. The paste can be ignited with another standard action by striking it from an adjacent square with a metal weapon or object. When thus ignited or otherwise exposed to fire, the jelly explodes, dealing 2d6 points of fire damage to creatures and unattended objects within the treated square. If the ignited square is adjacent to another square containing blasting jelly, that square ignites as well.
The question is pretty straightforward: can I apply multiple doses of Blasting Jelly to the same 5' grid square? Assuming that's possible, would the damage stack?