Transmission electron microscopy(TEM) is applicable to both filled and unfilled elastomer blends. However, for most elastomer combinations, there is no contrast between the polymer phases in aTEM. If the polymers differ signifi- cantly in unsaturation, osmium tetroxide(OsO4) or ruthenium tetroxide(Ruo4) staining is the best method for obtaining contrast. The metal oxides selectively oxidize the unsaturation and the location of the metal atoms in the phase with the greater unsaturation provides the electron density contrast for TEM. Contrast for TEM analysis of elastomer blends of diene rubbers is achieved through the sulfur hardening method developed by Roninger, 1933 and utilized by Smith and Andries, 1986. Small rubber specimens are immersed in a molten mixture of sulfur, an accelerator, and zinc stearate. The selective absorption of the zinc salts into the SBR results in phase contrast darker than the BR in a TEM