Any people quote, "Hubble, bubble, toil and trouble" as the witches' famous line in Shakespeare's play, Macbeth (Act 4, Scene 1, vv. 10-11). So the general populace might assume the quote is correct. But it is not. The real quote is "double, double, toil and trouble." The incorrect quote is assumed bona fide because of its repeated use. This article discusses similar assumptions made about many coating specifications and the trouble the assumptions cause. In the discussion, the toil is in the tests. Aside from the use of successful track records, it is common for coating specifications to be based on test criteria deemed important by specification authorities. But are the tests relevant to the intended service environment? Has the meaning of the test data been misinterpreted? Have the tests been ascribed a level of accuracy and dependency that the test method simply cannot deliver? These vital questions, addressed in this article, must be considered if a coating specification is to be supported in a meaningful way and to prevent all sorts of problems.
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