When stainless steel is impractical and zirconium oxide unnecessary, 4 mm acid washed silica beads are a good choice for standard laboratory applications. These large glass beads can also be used in conjunction with smaller zirconium and silica beads to form mixed matrix disruption tubes. Silica beads are more economical than zirconium silicates and oxides, while often as effective. Acid washed silica beads are treated with acidified water to remove fine particles, dust, and other impurities typically found in untreated beads. They are further baked to drive off organic impurities.