How to Apply Signs and Decals
Most decal failures are surface preparation failures. Get the surface right and the adhesive does the rest.
Clean first, properly
Wash the area with detergent and water, then go over it again with isopropyl alcohol to remove wax, polish and grease. Household glass cleaners leave a residue that stops adhesive keying to the surface, so avoid them. Let it dry completely.
Watch the temperature
Adhesive struggles in the cold and goes tacky in extreme heat. Aim for a mild day, in shade, on a surface that isn't hot to touch. A panel sitting in the Queensland sun is too hot to apply to.
Position before you commit
Tape the decal in place along one edge and stand back. Once the backing comes off you get one attempt. For larger kits, a hinge of masking tape down the centre lets you work outward from the middle.
Work the air out
Apply from the centre outward with a squeegee or a felt-edged applicator, using firm overlapping strokes. Small bubbles will often disappear over the following days as the adhesive settles. Larger ones can be pierced with a fine pin and pressed flat.
Then leave it alone
Adhesive takes time to reach full strength. Keep the surface dry and avoid pressure washing directly over the edges for the first few days.
Wet application
For large panels, a light mist of water with a drop of detergent lets you slide the decal into position before squeegeeing the water out. It buys you time, but it also extends the drying period considerably.