These EMD Science ColorpHast strips are designed for easy colorimetric indication of pH. The strips can be immersed in the sample for a long period of time, so weakly buffered solutions can be tested with accuracy. Just dip the strip in your solution and match the exact color of the pH on the strip to that of the box-it's that easy. There is no bleeding of dye, even in strongly alkaline solutions. pH paper strip show a distinct color change for each full pH unit change from pH 0 to 14.