Editor’s note: This article is the second in a series addressing technical questions regarding windshield repair, courtesy of the National Glass Association’s National Windshield Repair Committee. For answers to these and other repair-related questions, visit www.windshieldrepair.org.
Q: I am thinking of investing in a windshield repair business. While researching the possibility, I came across the term "dry vac.” What does it mean?
A: When repairing rock chips, the goal is to remove the air from the break and get a quality resin into the cracks and crevices. “Dry vac” refers to a process where the repair equipment creates a vacuum that removes the air from the damaged area before resin is released into the break. The vacuum helps pull the resin into the cracks and crevices. Another method involves depositing the resin first, and then vacuuming the air out through it. Both methods work; it is largely a matter of personal preference which one you choose.
Q: What is the purpose of the acid in windshield repair resin? Why is it important and what role does the viscosity play?
A: The acid causes the resin and glass to chemically bond; the resin molecules bond with the glass molecules. This chemical bond is important because it can withstand the expansions and contractions a windshield experiences when exposed to extreme temperature changes. The higher the viscosity, the higher the molecular weight; meaning there are more molecules to crosslink, resulting in a superior bond.
Q: My company does a lot of repairs. How can I save money on perishables?
A: Use Mylar-film cure tabs. Overhead projector sheets cut into squares work great. Purchase resin by the liter for significant savings. Also, purchase O-rings and seals through O-ring manufacturers to save on costs.