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Surface Finishing Tutorial

#112 Cleanliness Testing Methods - 2

Category : Metal cleaning
February10, 2012
(4) Spray pattern test

This test evolved from practices of blowing breath on dirty glass surfaces to determine the cleanliness, and is performed by spraying cold and clean water in fine mists onto the test panel. Recommended spraying distance would be approximately 60cm to avoid water extravasation on the surface. The soiled areas will appear obviously like a map pattern. The compressed air source used for this test must of course be free of oils, water and dust particles. After spraying, the test panel will be tilted to remove the excess water as not to cause any drying. The test requires shorter time for heavily soiled panels and longer time for cleaner panels.

There is an improved version of this test that uses a box with a clear acrylic panel with grid lines forming 100 squares. The test panel already sprayed with water is placed inside of this box and view through the grids, and the soil map is traced with felt marker to quantify the cleanliness as a %. [Fig.1] shows a pattern traced by this method.

[Fig.1] Cleanliness pattern

(5) Atomizer test

This test is a evolved version of the spray pattern test. The difference from it that the evolved version is performed on dry surfaces and dye is added to the water so the pattern will remain even of the water evaporates. As shown in [Fig.2], distilled water is atomized with approx. 450mmHg air sprayed on the test panel at approx. 60cm distance. It takes 30~40 seconds to see where it is soiled and where it is clean.

[Fig.2] Atomizer test

After spraying, a heat lamp is used to dry the surface to reveal the dyed areas where water adhered. The atomized water droplets are finer than the conventional spray method, minute soiling can be detected.

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