The importance of a good seal

When installing a new windshield, we have to use a caulking gun to place a steady bead of urethane glue. This is the glue that keep the window attached to the body of the car. It is extremely strong and can withstand cold and hot temperatures.

There are a few very important things to know about using urethane, and a lot of it comes with years of experience with using it. One thing that many people neglect, is that it needs a special chemical to actually bond to a surface. Without this primer, it will just peel off. The other most important factor, is that you need to know exactly how much to use, and how to place it to get the best seal possible.

Many people think that more glue is better. It makes sense if you think about it. The truth is, there is a “sweet spot” for the exact amount that you should use, and it varies between vehicles.

In the picture below, you can see a nice steady line of urethane has been holding this windshield attached. Also, this is the ideal amount and it stays consistent the whole way through.

The bottom most black line is the urethane seal.

In the next section, there is a video where you can see what the seal should NOT look like. If you notice, there is no seal at all. This is something that we come across a little too often. It also proves to us that there are still some inexperienced installers that are neglecting the use of proper installation methods.

And lastly, we will sometimes see the work of somebody who took it on themselves to install their own windows. This goes to show that, even with the right tools and supplies, you still need to know how to use them to do the job right.


It isn’t very common, but some installers do this “zig-zag” pattern to place the urethane on the body of the vehicle. Again, it seems like it makes sense, but this is a nightmare for any chance of a possible good seal.

The biggest concern is that you won’t even notice that a job was done poorly until it’s too late. In an industry that requires lots of experience, the term “you get what you payed for” is an understatement.

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