4184.01 DESCRIPTION.
This specification covers two types of glass spheres, coated and uncoated, for the production of reflectorized pavement markings. Waterborne traffic paint shall use dual coated beads (silicone and silane). Epoxy pavement markings shall use silicone only coated beads (no silane). VOC compliant, solvent borne paint shall use uncoated beads.

The glass spheres shall be transparent, clear, colorless, and free from milkiness, dark particles, and excessive air inclusions. They shall be essentially clear from surface scarring or scratching. The glass spheres shall be free of hard lumps and clusters and shall dispense readily under any conditions suitable for paint striping.

4184.02 SPECIFIC REQUIREMENTS.

A. Gradation.
The glass spheres shall meet the gradation requirements for type as given below:

Sieve Size	Percent Passing
16 (1180 µm) 20 (850 µm) 30 (600 µm) 50 (300 µm) 100 (150 µm)	100 95-100 75-95 15-35 0-5

B. Roundness.
The glass spheres shall have a minimum of 80% true spheres.

C. Refractive Index.
The glass spheres shall have a minimum refractive index of 1.50.

D. Properties of Dual Coated Spheres.
The glass spheres shall be coated with a dual coating. The coating shall have both a moisture resistant silicone coating and an adhesion promoting silane coating. The spheres shall pass the moisture resistance test and the adherence coating test.

E. Properties of Silicone Coated Spheres.
The glass spheres shall be coated only with a silicone coating (no silane). The spheres shall pass the moisture resistance test and shall test negative for the adherence coating test.

F. Properties of Uncoated Spheres.
The glass spheres shall pass the free flow test.