The Window Tint Dot Matrix Dilemma
Anyone that has installed window film on a car is familiar with the dilemma of how to get the dot matrix areas to look good and consistent. Installers have tried everything from sanding the matrix to using glue sticks to combat the issue. Some have given up completely and just install solid black vinyl over the matrix area and but seam the window film to the vinyl.
Why is this issue so difficult to overcome? Well, with the exception of installing vinyl, one strategy will not work for all situations. In an effort to add some clarity to this issue, I wanted to detail out the various issues with dot matrix and the primary ways that installers are currently addressing the dot matrix dilemma.
To begin with, there are two main issues that installers deal with regarding dot matrix during a window film installation. The first is getting window film to stick properly in the matrix area. Often the film will want to peel back and not want to stick in this area. After discussing this with people in the glass industry, this issue stems from the fact that many of the materials that matrix is comprised of are designed to be resistant to things adhering to them. As a result, we are fighting the natural tendency of the material by trying to adhere something to it. As an illustration, think of trying to get things to stick to the inside of a Teflon coated pan. try as you might, things just do not want to adhere.
The second issue is that the installer can get the film to adhere to the dots, but the film appears to have a “silvering” in the matrix area when viewed from the outside. (See Picture) To make matters worse, this “silvering is often not uniform or consistent across the window drawing even more attention to this problem.
So, what can we do to combat these issues. Let’s tackle the first issue of the film not wanting to adhere to the matrix. The most common strategy for this is to use something to scuff the surface of the matrix area knocking off the top coat and creating a rougher surface that the film has an easier time adhering to. This method is often used in combination with a adhesive promoting solution. The idea is to make the material more conducive to the film adhering and then giving the adhesive the added boost of an adhesion promoter. This tends to work well at getting the film to stick to the glass, but the issue of “silvering” might still be present.
What causes the silvering? The basic explanation is that the profile of the dots serve to keep the film floating above the actual surface of the glass. The dots are spaced too closely together and the film rides on the top of the dots unable to deflect into the valleys between the dots to stick to the actual glass. The resulting gap between the glass and the film in these areas is what you are seeing when “silvering” is present. You may notice that as the film cures that you can push down in these areas and reduce or eliminate the silvering. This is because once the mounting solution is completely dried out you can often push the film into these valleys and get it to stick to the glass. Often, even you are successful getting this to occur, the “silvering” will return to these areas again as the film cannot maintain adhesion in these valleys. again, the use of adhesive promoters in these areas might help this, but getting uniform adhesion across the entire matrix is difficult.
The only way to truly take care of silvering is to fill in the gaps left when the film rides on the top of the dots. This is often done through the use of a clear glue stick. The idea is to fold back the film to just below the matrix and run a bead of glue at the juncture of the film to glass. Then lay the film back down and squeegee the glue line evenly through the matrix. The excess glue will flood the valleys between the dots and eliminate the “silvering” as that gap is now filled with glue.
The last option is to trim the window film just below the matrix and apply a black vinyl in the area that the matrix exists. This can be done very neatly via a butt seam method and give goo visual results from the exterior. However, it does change the look of the window from the inside and some customers might want that.
I hope this explanation helps some of you deal with this pesky issue. As always, your experience might vary from this and these are just suggestions. Please try these and other methods at your own discretion and take precautions to not do any damage to the vehicle you are working on.