If you buy glass beads for road markings, one of the first questions is whether you need drop-on beads or premix (intermix) beads. The two do different jobs, and choosing wrong costs reflectivity, durability or both.
What drop-on beads do
Drop-on (surface-applied) beads are sprayed onto freshly painted or extruded thermoplastic markings. Part of each bead sinks into the binder; the exposed upper half turns headlight beams back toward the driver. They deliver reflectivity immediately after application, which is why they are standard for hot-melt and cold-paint road markings.
What premix beads do
Premix beads are blended into the thermoplastic or paint before application. As traffic wears the surface, new beads are exposed, so the line keeps reflecting for its whole service life. They are typically specified with drop-on beads in a two-layer system.
Quick comparison
- Timing: drop-on = instant reflection; premix = long-term reflection as the line wears.
- Typical use: drop-on for new markings and re-marking; premix for durable thermoplastic layers.
- Grading: regional specs split the two – e.g. EN 1423 covers drop-on beads while EN 1424 covers premix; AASHTO M247 types are often mapped to application method.
Side-by-side comparison
The two application methods are not competing products. Most well-specified road markings use both: premix beads inside the material to provide a baseline of retroreflectivity that survives wear, and drop-on beads on the surface to deliver immediate and high initial brightness.
| Parameter | Drop-on beads | Premix beads |
|---|---|---|
| Where the bead sits | On the surface of the wet film | Distributed through the marking material |
| Typical mesh range | 20–80 | 60–140 |
| Application rate | 350–500 g/m² | 200–400 g/m² depending on film thickness |
| Initial retroreflectivity | High, immediate once cured | Lower initially, improves as the surface wears |
| Performance over time | Falls as beads are worn away or lost | Replenishes as the binder wears back |
| Equipment needed | Drop-on gun or bead dispenser | Inline mixing into the marking material |
| Main failure mode | Over-application causes bead burial | Under-application leaves a dull marking |
| Best suited to | Thick markings, high-visibility requirements | Thin films, thermoplastic and cold plastic systems |
How much to apply
Typical field guidance is 300-450 g/m² drop-on for thermoplastic and 250-350 g/m² for paint. Premix loading usually sits between 10% and 20% of the thermoplastic weight. Confirm the ratio with your marking-material supplier and the project spec before ordering.
Setting the application rate
Application rate is where most marking projects gain or lose their retroreflectivity. Too little and the marking never reaches the specified RL; too much and the beads bury each other in the binder, which reduces performance and wastes media.
| Marking type | Film thickness | Drop-on rate | Watch out for |
|---|---|---|---|
| Thin film paint | 0.3–0.5 mm | 350–400 g/m² | Beads sinking into a thin binder |
| Standard paint | 0.5–0.8 mm | 400–450 g/m² | Uneven spread at the edges of the stripe |
| Thick film and high-build | 1.0–2.0 mm | 450–500 g/m² | Bead burial if the film is still soft at application |
| Thermoplastic | 2.0–3.0 mm | 400–500 g/m² | Timing: beads must land before the surface skins over |
| Cold plastic | 1.5–3.0 mm | 400–500 g/m² | Cure speed varies with ambient temperature |
Treat these as starting points and tune on a test section. The correct rate depends on the binder, the bead grading and the ambient conditions on the day, none of which are captured by a catalogue figure.
Buying from Linghang
Linghang (Yongqing Linghang Glass Bead Co., Ltd., Hebei) manufactures drop-on road-marking beads in mesh 20-40 and 20-100, plus premix grades, with roundness ≥80% and refractive index 1.5. High-brightness drop-on beads are available where night visibility is critical. See our road-marking glass beads or premix/composite beads. Grading against AASHTO M247, EN 1423/1424, BS 6088 and GB/T 24722 can be arranged – ask for test reports with your sample.
For a fuller technical treatment of Drop-On vs Premix, see our guide: Drop-On vs Premix Glass Beads: The Technical Difference and How to Spec Both.
Related reading
- Why Beads Fail — road marking selection
- Night Visibility — road marking selection
- Spec Checklist — road marking selection