Glass Bead Know-how Will Boost Retroreflectivity
Retroreflectivity, the reflecting of light (such as from a car’s headlights) back to its source, is the latest buzzword in our industry, driven by federal and state mandates that put line brightness at the top of performance factors. Retroreflectivity is a product of several factors, however; the paint, glass beads, equipment, the application method and the conditions under which the markings are applied all affect the long-term brightness of the line.

A properly installed marking will have the appropriate mil thickness of paint and will have glass beads embedded in the line with about 60% embedment of the bead. In order to ensure proper line brightness, a minimum requirement of beads per gallon of paint is specified.

To be sure that the beads stay on the marking, adjust your equipment so the bead pattern matches the line. It’s a common mistake to apply a fan of beads wider than the line, or to inadvertently apply beads to one side of the line or the other.

You may also have to adjust your striping speed; if the beads hit the line at too great a speed and angle, they may bounce off onto the roadway and be lost. Although our industry emphasizes speed, when it comes to quality, faster is not always better. If you want to stripe faster, work with your equipment vendor to ensure that your striper is engineered for higher speeds.

This being said, the component of the line that actually reflects the light back to the driver is the glass bead. You don’t necessarily have to spend a lot more to get better quality. It’s more important to develop a relationship with your material vendor to ensure you get the best value.

Here are a few characteristics of quality beads:

Roundness
The more perfectly round the bead, the more true the light reflects back to its source, providing visibility of the marking in low-light conditions. Industry-wide, approximately 80% rounds is the standard for glass beads, with products available with higher than 90% rounds if you're willing to pay the price.

Clarity
The clarity or lack of color in your beads affects the percentage of light that passes through the bead and reflects back, or brightness of the bead. Since glass beads are manufactured from waste and by-product glass, your beads are only as clear as the raw materials used to make them. Quality bead manufacturers are very careful with their raw materials sources.

Coatings
Glass beads are available with a variety of coatings to help the bead adhere to the paint, contribute to wicking of the paint up around the bead to provide 60% coverage, or to help the bead float or sink in the paint. For optimum brightness of the marking, be sure to match your glass beads to the formulation of the paint you are using. Your paint and bead manufacturers should be able to recommend appropriate products.

Glass beads need to be handled right to perform well. They should be stored in a dry place, as moist beads will not pass through the striping equipment properly; and care should be taken when loading your equipment with beads to ensure that bits of paper and other foreign material aren’t put into the tank. While this foreign matter may flow through the gun without plugging the nozzle, it could restrict the proper application rate.

The key to quality control is monitoring and documentation of the application process. For more information about material monitoring systems and glass bead application, call EZ-Liner at 800-373-4016.