Agglomerated gold nanoparticle clusters embedded in polyelectrolyte films are optically excited, which results in local ablation of material from the polyelectrolyte films and in some cases leads to the formation of a gas bubble. Evidence is given that this process is mediated by superheating of the medium around the excited gold nanoparticle clusters. This process is highly dependent on the medium used. Besides the boiling point, salt and proteins in the medium also affect the formation of gas bubbles. These data demonstrate that the type of medium must be considered when describing light-mediated heating of gold nanoparticle clusters, which are fixed in a matrix surrounded by medium.