Preparation—Glass Part 1

Preparing for the installation is the step where many technicians make their biggest mistakes. The removal and installation steps, where skill and experience are demonstrated, are the parts every tech brags about. However, preparation is what separates the men from the boys. This is where the bonding begins and the mistakes happen.

There are three sub-sections to the preparation step: glass preparation, pinchweld preparation and preparing for the installation of the glass in the opening. Today we will deal with the first part of glass preparation, making sure the glass is free of contaminants.

Chemists tell me that improper cleaning of the glass surface is the number one reason for adhesion failure of the glass to the body of the vehicle. This can be caused by the wrong glass cleaner, the wrong wipes, the wrong handling of stubborn contaminants, or the procedure itself.

The first rule should be to use the type and brand of glass cleaner recommended by your adhesive manufacturer. Doesn’t it make sense to use products that have been tried and tested in the lab? At the very least follow their recommendations as to what criteria is important in selecting a glass cleaner.

Glass cleaners should not contain ammonia, excessive alcohols, anti-static properties, scented oils, silicones or petroleum byproducts. I have found that foaming glass cleaner is better than non-foaming because it helps find oil based contaminants by dissipation of the foam upon application. Whatever cleaner you choose should be discussed with your adhesive rep to make sure it is compatible with your urethane.

Use disposable wipes, not shop towels to wash the glass. Towels may seem more cost effective, but the result is an ineffective bond. Remember that shop towels are washed by the towel service with other towels from other customers. The other customers could be mechanics shops, oil change centers or collision centers. They are washed with harsh chemicals to clean them. Once you add a cleaning solution to the glass and wipe with a shop towel, some of these chemicals are released and applied to the bonding surface thus hindering adhesion. The best cleaning wipes are good old disposable paper towels that are used once and thrown away.

What about the stubborn tape residue or manufacturing release agent used in the encapsulation process? How do we get that off or do we have to? There are now abrasive materials available to remove these types of contaminants. I strongly suggest that you use these products and follow manufacturers’ instructions carefully to best prepare the surface for bonding.

All customers like clean and shiny windshields but don’t forget that the bonding edge is the most important part of the glass to clean, not the transparent center. We can always shine it up after the installation. The wipes are never as clean as when taken from the roll or box. This is why we clean the edges first. The procedure for cleaning the glass is as follows:

—Spray the edge with foaming glass cleaner and notice any dissipation of the foam. If there is some dissipation, scrub that areas of dissipation firmly with a clean lint-free paper towel and re-spray the area again to test.

—If there is additional dissipation or other residue present, utilize the product or procedure recommended by your adhesive manufacturer. This can include the application of an abrasive cleaner or wet scrubbing of the area or both.

—Once the edges are free from contaminants wash the remainder of the interior surface from the edges to the center.

—Make sure that the edges are perfectly dry before application of primers or preps.