by Bob Beranek

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.


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


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.


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.

Removing the old glass has always been the most difficult part of the installation process because of the physical labor required. However, the introduction of new hand tools, particularly power tools, has greatly eased this part of the installation. Remember, the goal is to get to the edge of the glass for easy cut-out. Once that is accomplished the rest is easy. To assure that the finished installation is both pleasing to the eye and safely bonded to the metal, here are some recommendations.

—Have replacement mouldings available, whether you think you will use them or not. It ensures that if even if the original mouldings were bent or misshaped, the job will always look good when finished. A good selection of universal mouldings comes in very handy to replace stretched or damaged mouldings.

—Have replacement clips as well. Even though clips are not used as often as they once were, some clips are unique. To make matter worse, many distributors do not stock a wide variety of clips because they don’t sell well and inventory turnover is low. I suggest determining the dominant car dealer in your market and obtaining the clips and retainers necessary to do those brands of vehicles. That way you will have replacements most of the time.

—Never disconnect the electrical components from the rear view mirror while the ignition is on. This could damage the vehicles’ computer or, at the very least, erase the pre-programmed memory. Either:

—Disconnect the wiring harnesses and remove the mirror and place it the back seat; or

—Remove the mirror from its pad and leave it hanging from its wiring harness.

—Pull the cowl panel. In most cases the cowl should be pulled to allow for the best bottom seal. The passenger-side airbag, in most cases, depends on the adhesion of the bottom seal of the windshield to position it properly. It also supports and solidifies the firewall. If the cowl is not pulled, the bottom seal cannot be assured and failure is a distinct possibility.

—When using hand tools for removal, start with the shortest blade in the cold knife and work up to the longer blade. This gives the technician more control of the tool and makes the cut out easier. Look for blades that have extra thinness, serration and coatings to protect the paint.

Use your body weight rather than your upper body strength to pull the cold knife. This allows you work more comfortably and reduces the chance of muscle strains or pulls.

—If you have a part with a rigid or metal-coated moulding system, use a plastic stick vertically to the pinchweld to break the moulding from the glass surface. Then force your cold knife blade between the glass edge and the broken moulding flap and under the edge of the glass. Then pull the cold knife normally. This method cuts out the glass and leaves the moulding in place which eliminates the need to pull the rigid moulding out to access the glass edge. The moulding also protects the pinchweld wall from damage from your tool.

—When using power tools, lubricate the tool by spraying water on the adhesive to be cut and on the blade itself. This reduces the harmful fumes caused by the high speed of the blades and also makes the tool work smoothly. Plain water is recommended over soapy water because it will not contaminate the bonding surface. All cut-out blades are flat on one side and beveled on the other. The flat side of the blade should be to the glass surface. The blade and the glass create a scissor-type action that eases the cut-out. The closer the cutting edge is to the power source the more torque and cutting power it has. So, use the shortest blade possible to cut the material and protect the interior trim.

Pre-inspection is one of the most important steps in a successful installation. It can mean the difference between good and bad customer relations as well as a safe or unsafe installation. The experienced technician not only looks at the inspection as creating a level playing field but also as an indication of how the installation is to proceed or if it can be done at all. It is also an opportunity to build a positive rapport with the customer.

All technicians know that they should complete a pre-inspection but many do not like to do it because they feel pointing out the defects on the vehicle will upset the customer and make them angry for being picky. If the tech does a pre-inspection the wrong way, yes, they will become agitated. That is why I suggest that the pre-inspection become an explanation of the installation process and the Pre-inspection Form become an Authorization Form.

Instead of pointing out every ding and scratch, rub your hands over the damage. The customer’s eyes will be attracted to your hand which means that they know you noticed the damage and you know that they saw it and no words were spoken. Instead of making a statement like, “there is a dent here and a scratch here,” ask a question or make a lighthearted statement to get you point across.

Items to look for are:

—Dents and scratches in the work area. Concentrate on the passenger side of the vehicle. The passenger side is the least noticed side of the vehicle, yet the most susceptible to damage.

—Early signs of corrosion. If corrosion is visible before mouldings are removed, it is an indication that there is more corrosion present under the glass or moulding. It may be necessary to discuss bodywork or the possibility of denying the installation entirely.

—Moulding fit. If the moulding is not fitting flush to the body or glass, it could indicate a previous installation or other hidden problems. This also should be discussed with the customer.

—Missing or damaged parts. This also can indicate a previous installation. It could mean the installation may take longer to complete to the customer’s satisfaction.

—Aftermarket paint jobs. Usually appears as “orange peel” texture, improper color matching or over spray on mouldings. This can indicate previous bodywork. This may cause problems with glass fit or paint pealing by removal of the moulding or protective tape.

—Interior stains or damage. Check the seats, floor, headliner and interior garnish mouldings. Some stains may indicate a leak that should be addressed before work begins. While others can mean that some exterior parts may be loose or misplaced causing water or air seepage.

—Electronic and mechanical items. These include; wipers, washers, radio, lights, window regulators, power door locks, rain/light sensors, remote start, etc. Make sure all mechanicals are in working order before beginning work or inoperable mechanicals are discussed with the owner.

It is always a good idea to inspect the vehicle in the customer’s presence. But if this is impossible an Authorization Form will help in making the inspection more professional. Complete the form and leave it for the customers along with their copy of the work order. The other option is to take pictures and electronically send them to the customer or attach them to the work order or invoice.