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Expert's Corner — test

Cross-Cut Test for Adhesion

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Cross-Cut Test for Adhesion

The proper test for determining if a paint or finish bonds well to the substrate, which could be just a previous coat of paint or finish, is called the cross-cut adhesion test. It is the standard that has been established by the American Society for Testing and Materials (ASTM). First, score the coating with the razor blade in a cross-hatch pattern with about one-sixteenth inch between cuts. Then press the masking tape over the cuts and pull it up quickly.The test is shown in the accompanying picture. To be totally accurate, you need a special cross-cut tester (the cutting tool),...

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TIP: Testing Your Finish for Hardness

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TIP: Testing Your Finish for Hardness

You can use architect’s pencils to test for finish hardness (scratch resistance). The lead in these pencils is rated from about 6 or 7B, the softest, to 6 or 7H, the hardest. HB is in the middle. You don’t need to buy all these pencils, just the middle five or six, because most finishes will test to one of these. To prepare the pencils sharpen them with a pocketknife, not a pencil sharpener. Then ground the tip of the lead perpendicular to the length of the pencil on fine sandpaper, or regular paper if the lead is close to flat....

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