TESTING FOR PRESENCE OF
MOISTURE-PROOF COATING ON GLASS BEADS
This test method is intended to determine if glass beads used to reflectorize traffic markings have a moisture-proof coating. A moisture-proof coating is obtained by coating the bead with silicone or with a dual coating, which is a combination of silicone and silane.
This test will only detect if a bead has a moisture-proof coating. It will not distinguish between a silicone coating and a dual coating.
NOTE: Waterborne paint requires a dual-coated bead. VOC-compliant, solvent-borne paint requires uncoated beads.
1. Paper cup or other small container suitable for holding water
1. Fill the cup with tap water.
2. Take a spoonful of beads and dip it into the cup for approximately five seconds, then remove.
Moisture-proof, coated beads (either silicone, or dual coated) will bead the water and will not be wetted. Uncoated beads will be thoroughly wetted and will become a clumped mass of beads.
NOTE: To determine if the beads have a dual coating, a sample must be sent into the Central Laboratory. This is a more involved test, which requires special chemicals and equipment.