Posca markers are quite unique, as their qualities depend on the surface you write on. On absorbent surfaces, like wood, cork or paper, they are permanent.
On non-absorbent surfaces, such as windows, black boards, PVC and balloons, they are non-permanent. It should be easy to remove the writing from the foil balloon with a soft, damp cloth.
Let us know if this works or if you found another way to wipe out the writing.
