Tech Sheet 16 - The Scotch Tape Test

To: Recolor Specialists
Subject: The Scotch Tape Test -- to assure good recolors

For those of you doing recolor work, here's a simple procedure that can save hours of extra work -- The Scotch Tape Test. Take just three or five minutes extra before spraying the entire job, or three or five hours after the customer calls you back for a re-do. It goes something like this, "A dealer telephoned and said the recolor I did yesterday is coming off."

With only minor variations the story is always the same. Some report the paint coming off in sheets. Some say it is chipping off. When asked if the Scotch Tape Test was done first, the reply is always "No". Not once in twenty-five years has the report been "I did the tape test first and now the paint is coming off". Never. This test assures the paint will not come off.

Quality assurance programs throughout the plastics industry use this test to ensure the adhesion of decorative coatings. As defined by the American Society of Testing Materials (ASTM), the test is simple: Razor blade cuts are made through the coating to form a grid of 1/8th inch squares. Scotch tape is then rubbed down firmly over the area and peeled back at a 50 degree angle to the surface and examined. The sticky side of the tape should show no trace of the coating.

Try it. After preparing the surface, degreasing with Multi Clean in water (the warmer the better for water) and/or Flex Solv, apply the coating in just a few small patches next to a button, pleat, or a welt. Dry these test patches briefly using your heat gun. Then with your snap off cutter or utility knife, crosshatch only through the coating. Complete the test as outlined in paragraph 3 (above). If all passed, proceed with the entire job. If a difficult to clean place like the button area failed, you know where to focus your surface prepping attention.

In the case of GM leather, the original surface should have been wet sanded with 320 or 400 grit carbide paper. The top clear coating (and occasionally the print coat beneath) on these cars is loaded with slip additive, as with newer Jaguars. Wet sanding keeps the paper from loading up and eliminates the dust problem. The multiple scratches increase surface area and the bite of your coating. Sanding also allows use of a milder solvent such as Flex Solv.

For the hard plastics (trim, quarter panels) including polypropylene, wet sanding followed with a professional-quality plastic primer is advised. Check with our Seattle office for the latest on recommended primers.

Note: One of the biggest morale killers around here is the failure of applicators to use the tape test as well as their ability to misinterpret its results.

If you find a Flex Proof product failing in adhesion please do the tape test and inspect the underside of the failed coating. 99 times out of one hundred (assuming proper prep work) you will find the original equipment coating failed to adhere to the substrate. This is to say, your Flex Proof coating stuck to the original coating but it failed to adhere to the base. In such cases you need to completely strip the original finish or you're wasting your time.