Dyes contrast to conventional indicator papers, are substantively bound to the cellulose fibers. As a result, the possibility of the color bleeding, even in strongly basic solutions, is avoided. Measurement of pH value is possible even in unbuffered or very weakly buffered solutions since the strips can be left in the solution until the final color change is completed. Will not contaminate samples and colors will not run into each other, 6 x 5MM indicator papers are sealed on a 6 x 85MM plastic strip. Sufficiently long to avoid contact between fingers and test sample.