IS 218 covers glass beads that are mixed into or dropped onto road marking paint to make it retroreflective (visible at night in headlights). The beads act as tiny retroreflectors, bouncing headlight beams back toward the driver. Critical for road safety.
Specification for glass beads used in retroreflective road marking paints covering size distribution, roundness, refractive index, and testing.
Key Values
RoundnessMin 70% spherical
Refractive indexMin 1.5
Drop-on bead rateTypically 300-400 g/m²
Practical Notes
! Glass beads must be dropped onto wet paint within seconds of application — timing is critical for embedment.