Many branded dilute-with-water windshield washer concentrates and ready-made windshield washer solutions now contain silicone-based chemicals that are designed to prevent road debris sticking to vehicles’ glass and to promote the beading of rain so that it blows off windshields and doesn’t smear when the wipers are used. This chemical additive builds into a bonded layer on anything it touches, including painted surfaces, and will also prevent applied self-adhesive materials from fully adhering. The layer is invisible, may be difficult to test for and detect, and must be removed before graphics are applied.
We recommend that in all cases where graphics are applied to side and rear vehicle glazing that the following cleaning regime is practiced:
1: Completely removed any obvious soiling with soap and water. Use dish washing soap. It does not contain waxes unlike many vehicle specific cleaning detergents.
2: When the glazing is dry, carefully clean the window again with a clean piece of tissue, kitchen paper is fine, that has been generously wetted with IPA (at least 70% and preferably higher) then dry with a second clean piece of kitchen paper.
3: Repeat 2 but paying particular attention to the edges of the glass.
4: Check for paper dust or adhering fibres before applying graphics as per further instructions relating to the material and its use.