Methods for pre-treating packaging materials of particular composition for use in conjunction with a scintillation crystal are disclosed. The packaging materials may comprise a reflecting material, an elastomer, a reflecting fluorocarbon polymer, a polymer or elastomer loaded with a reflecting inorganic powder (including a reflecting inorganic powder comprising a high reflectance material selected from the group comprising Al2O3, TiO2, BN, MgO, BaSO4 and mixtures thereof), or a highly reflective metal foil selected from the group comprising Ag and Al that is chemically compatible with the scintillator crystal. The scintillator crystal may comprise a crystal selected from the group comprising NaI(Tl), LaBr3:Ce, La—Cl3:Ce, La-halides, and La-mixed halides. The method includes subjecting a scintillator packaging material to a pre-treatment while in package form, said treatment selected from the group consisting of heating to a temperature exceeding a proposed operating temperature of the scintillator package, and placing the packaging material under pressure in a confined space until the packaging material is in final form.