The Pre-Stretch and Shrink Method
What is the Pre-Stretch and Shrink Method for Vehicle Graphics?
In a nutshell, the Pre-Stretch and Shrink Method goes like this:
- Heat
- Stretch
- Apply, and
- Shrink
This takes full advantage of the film’s memory effects when conforming around the curves. Notice pulling a film outward, the film curves in a direction perpendicular to the stretch. When pulling to the midpoint of opposite edges, for example, that’s where the tension is. And these stretches, without any stretch, fold down.
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Now, let’s add two rods to show where the Pre-Stretch and Shrink works. Rather than stretching the film only from the midpoints, these rods will allow the film to stretch evenly.
Wrapping Compound Curves on a Vehicle
Let’s look at the door handle to see the Pre-Stretch and Shrink Method in action.
Improper Technique of the Pre-Stretch and Shrink Method:
If we were to apply film over the door handle, with no pre-stretching, and add heat, the film would simply lie flat over the area. We would then need to stretch it to conform to the handle.
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Instead, let’s let the film’s memory do the work.
Proper Technique of the Pre-Stretch and Shrink Method:
Step 1: Heat
First, I’ll fold the rods and apply heat to the film. (105ºF – 120ºF/ 40ºC – 50ºC)
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Step 2: Stretch
Then, I’ll stretch the film by at least 30%. Remember, we would always want to stretch the film perpendicular to the curve.
Remove the heat and let the film cool down in its stretched form.
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Step 3: Apply
I’ll then remove the rods and apply it to the flat section of this door handle. Where the film has been applied, the stretch will be fixed.
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Step 4: Shrink
Now, when I apply heat to the apply section, it wraps itself around the door handle.
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This technique can be used on all compound curves of the vehicle. Front and rear bumpers, cant rail, door handles, side view mirrors, small spoilers, and corners. The Pre-Stretch and Shrink Method will allow you to take advantage of the natural behavior of the film. So remember: Heat, Stretch, Apply, and Shrink.
