degrading
Worst of all, when plastics weep and bleed they can corrupt everything around them. Chemicals evaporate from their surface and acidify any moisture inside a display case. This causes mini bouts of acid rain that in turn eat away at the plastic in nearby objects—as well as any cloth, metal, or paper in those objects. Curators can lay down special carbon cloths beneath a plastic object to absorb some acid, but some plastics have to be quarantined immediately. Museums have also used plastics to coat nonplastic objects like silver (to prevent tarnishing) and paintings (to prevent flaking). But plastic coatings often "bloom" and turn opaque or "crizzle" (i.e., wrinkle) like dried rubber cement, changes that can damage the very object the coating was meant to preserve.