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Materials and methods utilizing a temporary visual indicator

  • US 5,837,645 A
  • Filed: 07/01/1996
  • Issued: 11/17/1998
  • Est. Priority Date: 05/13/1993
  • Status: Expired due to Fees
First Claim
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1. A method for marking a surface with a temporary visual indicator comprising:

  • (a) applying an indicator to the surface at a first pH, the indicator being invisible at the first pH and visible at a second pH;

    (b) applying a pH-modifying substance to the surface in an amount sufficient to adjust the pH of the indicator to the second pH and which evaporates or degrades, thereby causing the pH to change to said first pH.

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