by Bob Beranek
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I just got back from the Auto Glass Safety Council’s Winter Meetings in wet and cool Florida just in time to shovel out our driveway from six inches of snow. What a winter!

As promised, I want to report on a few issues that were discussed in the Standards Committee meeting and around the water cooler. In addition, I’d like your help with a couple issues that have come up recently.

1. Procedures for Pinchweld Preparation: In my last post we discussed the proper procedures for preparing the existing bead after the glass was removed with a new wire-out tool. Jeff Olive of Glasspro approached some adhesive representatives before our meetings and got their recommendations concerning this issue. They all said the same thing, trim back to 1-2mm and bond accordingly. Trimming the existing bead back assures the removal of any contaminants and makes the bonding surface even and acceptable for fresh urethane.

2. Salvaged/Used Glass: Though this is not a new issue, it was again brought up for discussion because there has been a push by the insurance industry to use salvaged glass in repaired vehicles. The committee spent a considerable amount of time discussing the matter and reviewing our original interpretation. The committee found that our Standard and the interpretation we originally published are still relevant and correct as it pertains to consumer safety.

Here are some new glass issues that I thought I would bring to the attention of the experts in the field, my readers.

1. There has been a rash of glass breakage recently when re-installing the rearview mirror to the mirror pads. Reportedly, this is happening on a variety of glass brands but most recently on Kia Rios, Chrysler 300 and Chargers. The reporter said that the mirror pad seemed tight to the glass without any cushioning. If any of you have heard or experienced this issue, please contact me, your glass distributor or manufacturer. I suspect that it could be caused by an aftermarket mirror pad adhesive but I want to hear more before I jump to any conclusions.

2. There has been a report of an audible ticking sound occurring on recent models of General Motors SUVs. The glass has never been changed but the ticking sounds like it comes from the dash or interior “A” pillar molding. When the glass is removed to fix the noise complaint, there is no indication of a problem. Once the windshield is re-installed, the noise is never heard again. I contacted my glass expert friends both here and overseas and they seemed to agree on the cause. It is not the glass but the glass mounting. The glass is sitting too low and is making contact with the plastic interior parts. When the temperature changes the glass will contract or expand thus causing the glass to rub or snap from the warmed plastic. To fix, use a rubber or plastic shim and force it between the glass and the dashboard or molding. You can R&I the windshield as well, but then you run a much greater risk of breaking the glass.

3. Dan Boehmer of Rolladeck and a past Auto Glass Week™ Technician Olympian contacted me about the 2011 Volvo XC60 windshields. He said that the OE and any dealer pre-primed windshield on this vehicle have a primer failure problem. The DOT number on the vehicle is 32, which is St. Gobain. There is a video on YouTube that illustrates the issue. Evidently, the primer applied along the top at the factory is deficient and peels right off with your fingers. If you have experienced this problem, please contact me as soon as possible so the vehicle and glass manufacturer can be contacted and informed of the problem.

Comment on this post, email me at bob@autoglassconsultants.com or call me at 800/695-5418.

The technicians in the field are the eyes and voices of the industry. Without you informing us of what you see, hear and experience we cannot protect the consumers from improper installation or manufacturing defects. Thank you all for your input and professionalism. Keep it up.

There was an interesting discussion recently that I thought I would bring up for readers to debate. The discussion is about the condition of the existing urethane bead once the glass is removed by the new wire-out tools. It seems that there is a belief that the bead is already trimmed to the proper height due to the design of the wire-out tools and that additional stripping is unnecessary. Also, there is some concern regarding the rough condition of the urethane bead when the new cord is used in the cut out. This brings to mind two questions.

Does the existing urethane bead need to be trimmed down or is the bead height adequate for bonding immediately?

What is the ideal surface for urethane bonding to itself, smooth or rough?

One of the selling points of the wire-out tool is that the existing urethane bead is cut closer to the pinchweld surface. This allows the technician to save time by not having to trim back the urethane bead for bonding. The directions given by adhesive manufacturers have been to trim back to 1-2 mm or 1/16” of the existing adhesive bead. The amount of bead left by the wire out tool depends on the design of the tool. The closer the wire is to the interior glass surface the closer the cut will be to the pinchweld. You will need to trim it back if there is more existing bead left by your particular tool. Remember that the 1-2 mm guideline is there for a reason and must be met as close as possible to the recommendation by the adhesive manufacturers.

There are basically two types of cut out material for the new wire-out tools, the wire or the cord. The wire cuts out the glass and leaves a smooth surface on the existing urethane bead. The cord usually leaves a rough surface. The smooth surface left by the wire is not a concern because we have been bonding to that type of smooth surface ever since we started to use urethane. The question that needs to be answered is what should be done with the rough surface left by the cord to promote adhesion?

Glass preparation is very important to the success of the bonding chain, but proper preparation of the body’s frame (the pinchweld) is equally important. In most cases we don’t actually prep the pinchweld, but we prep the bonding surface applied to the pinchweld. The bonding surface is most often the existing original bead of urethane applied by the vehicle manufacturer, but it could be the OE paint, OE primer or aftermarket primer. In any case, the bonding must be attained by following the adhesive manufacturer’s instructions exactly as written.

The first universal understanding of bonding adhesives is that an adhesive will always adhere better to itself, or its chemical twin, than to any other surface. Thus, urethane adheres better to urethane than it does to other surfaces or coatings. That being said, it is our goal to reach a pure uncontaminated urethane surface to which we will bond. Getting there is the skilled part of the installation.

Our goal should be to cut out the glass from the vehicle and strip the urethane from the body cleanly without scratching any of the painted surfaces. And, in a perfect world, all technicians would cleanly re-install the glass without any excessive urethane oozing to the pinchweld wall leaving 1-2 mm (millimeter) of original urethane by which the next technician could replicate the first installation and so on and so on. However, that is not how things are in the real world. Many times the technician finds improper prior installations, sloppy body work or corrosion that has to be treated. This means that pinchweld preparation is more difficult to attain and experienced decision-making must be implemented to correct the problem or create the proper bond.

The next series of posts I plan to share is how we deal with each of the situations that might present itself in preparation of the bonding surface. All of these discussions are in the adhesive instructions of your chosen urethane product, but I have found that the instructions are either forgotten or seldom taught because they are not followed or understood universally.

Basic Body Preparation

The basic body preparation instruction is the first one that every urethane manufacturer prints in their instructions and teaches. The reason is because it is the scenario that is most commonly seen by the technician; it is the simplest to explain, easiest in theory and most cost effective.

Simplest

Remove the glass, trim back the existing urethane to 1-2 mm (1/16 of an inch), apply urethane and set the glass.

Easiest

There is no need to add primer to the existing bead because urethane sticks best too itself.

Cost Effective

If there are no scratches caused, no primer is needed and cost can be reduced.

BobPinchweldPhoto

This is the perfect world scenario that unfortunately many of us see only seldom due to the issues named above. However, we should keep trying to attain this perfect bonding scenario because it is the simplest, easiest and least expensive way to go. We can increase the frequency of this basic preparation with the use of technologically advanced tools and the implementation of improved technique. Eliminate scratches and contamination and you have contributed greatly to the steps necessary to the perfect installation.

What do I mean by technologically advanced tools and improved technique? I mean the new wire-out tools, power tools and how they’re used, and special cold knife blades all contribute to less body damage. Strip out tools and the techniques in stripping the urethane from the body also reduce the chance of paint damage. Less body damage means less additional preparation is needed for bonding and more profits are realized due to increased productivity.

Next week we will look at the more challenging body preparation issues.