A precision method for surface testing pH of a variety of materials. Readings closely approximate those made with the pH interchange meter. Tests are conducted by using distilled water on the surface to be tested, make a mark with the pencil, and wait a few minutes until color stabilizes and match to chart. The narrower the range pencil, the more accurate the reading it provides in that specific range. Pencils are available: full range only 0 - 13. Box contains 3 pH pencils.