I was reading an interesting story about filming the miniature spaceships in Mexico for the movie Dune. To keep flies and mosquitos away and to avoid the insects landing or flying around the models, they sprew insecticides on the set and directly on the miniatures. Considering the heat and the long filming hours I guess if the models got any damage from this kind of treatment. I wouldn't be surprised if they still have a 30 years old Raid spray covering under the dust sheets. Perhaps some owner of original model props from Dune can confirm that.