Even the most experienced graphics installer may find it challenging to wrap a vehicle’s side-view mirrors, with their compound contours – especially forming
a strong bond on the film’s edges. We’d like to offer a solution that you may not have tried: pre-stretching the film.
About a year ago, we learned from our colleagues at 3M Germany a pre-stretching technique for cast vinyl films that works great when wrapping such surfaces
as side-view mirrors on vehicles, and motorcycle helmets.
Let’s start by reviewing the traditional method, where film is applied to the flat area of a mirror without first being stretched. Using that procedure, you
heat and stretch the film toward the outside edge of the mirror. This puts most of the stress on the outside edge of the film, where it can then pull back and form
wrinkles that look like fingers. With the pre-stretching technique, however, the entire film is heated and stretched before the application. This distributes the stress
over the entire piece of film rather than concentrating it in one area. When the film is then reheated during installation, it shrinks to conform to the edge of the
mirror, with low stress.
How to pre-stretch the film
When preparing the film for wrapping a mirror, first attach the length of film to a window pillar (note that the tape line marks the film’s original length).
Then, heat the film uniformly.
When the film is hot, pull apart and down several inches (again, notice the tape line marks the film’s original length).
Tack the bottom edge of the film to the door. Let it cool for a minute or so. Then you can apply the pre-stretched film to the mirror.
Applying the pre-stretched film
Prime all the edges – outside and inside the mirror’s frame – using
3M™ Tape Primer 94 which promotes adhesion.
Apply the pre-stretched film to the flat area of the mirror.
Then heat and wrap the film around the mirror’s edge. Because the film has been pre-stretched, it shrinks when heated to conform to the edge of the mirror with low stress. Trim the film as necessary. For even greater durability, wrap the film around the edge and tuck it in about a half-inch, all the way around the inside of the mirror. Again, use tape primer 94 for improved adhesion.
Make it a successful installation
In addition to the above tips, make sure you start with a clean, dry surface and follow other basic pre- and post-installation steps. Taking shortcuts at any stage increases the likelihood of a wrap’s failure (for example, wrinkles forming around the mirror).
See Demonstration of Pre-stretched Technique
Watch 3M wrap expert, Marcio Oliveira, wrap a side-view mirror using the pre-stretching technique and then give it a try yourself.