Even if polycarbonate sheet was covered with a surface protection film, you should always consider the surface contaminated. That means that you must clean the sign face before applying the graphics. Before you prep the substrate with a solvent or detergent, carefully read the manufacturer’s instructions. For most plastic-sheet applications, the most reliable cleaning method is a non-abrasive detergent and water. Solvents subject any type of plastic sheets to chemical stress, which can cause cracking.
Some professional decal installers only apply vinyl dry. In most cases, I agree that dry application is preferable. However, applying a translucent vinyl to a plastic sign face is the exception to the rule, because the static in a plastic sign face tends to attract vinyl like a magnet. Using a application fluid will kill the static. This is one of those times in which a wet application is better than doing it dry.
You can make your own application fluid by mixing 1/2 teaspoon of a dishwashing detergent, 1/2 teaspoon of isopropyl alcohol and 20 oz. of water. If you make your own concoction, don’t use dishwashing liquid that contains moisturizing lotions, which contaminate the vinyl’s adhesive and create failure.
I prefer using a commercial application fluid, such as Rapid Tac, Window Juice or Splash. Let’s face it. What is the likelihood that the guy assigned to mix up the application fluid is going to measure anything? Not too likely. On top of that, he will probably dump in the first thing that he finds into the water. Do you really think that he will care a wit about the potential contamination of the vinyl’s adhesive from surfactants or moisturizers? Even more unlikely.
Avoid any potential problems and just buy a premixed application fluid. Now that you’re ready to do your application, here are a few more pearls of wisdom which should improve your odds of success.
Use the minimum amount to accomplish the task. Lightly mist the surface with the fluid; an excess can create unwanted residue. If the liner gets wet, the silicon layer can flake off and contaminate the adhesive. When the sign is illuminated, these areas appear as dark blotches.
When applying graphics, start in the center. Apply enough squeegee pressure to force any application fluid from under the vinyl, and always use overlapping strokes. After removing the application tape, re-squeegee the entire graphic using a squeegee covered with a low-friction sleeve. This protects the vinyl from scratches.
When working with translucent films, avoid seams if you can. When translucent films overlap, the seam will be noticeable when the sign box is illuminated. Of course, overlaps aren’t always avoidable, but keep them to a minimum. Seams generally shouldn’t exceed 1/16 in. Abutting films can shrink and leave a noticeable gap when the sign is lit.
The film’s light and color transmission can vary from roll to roll — sometimes, even within a single roll. Therefore, overlap films from the same roll or lot number. Even then, color variations and inconsistencies can occur within the same roll. For this reason, if a film needs to be seamed, take the time to match colors to ensure consistent appearance.
