pH Indicator Pencil

This pencil quickly measures whether the pH of paper or paperboard is acid or basic. It contains an acid-base indicator, Chlorophenol red that reacts when it comes in contact with paper or paperboard. The marks made with this pen are violet when they are applied to neutral or basic paper and paperboard, they become yellow on an acid sample. If the pen tip dries out, moisturize it with a drop of distilled water.

N.B.  : A test conducted with a dried out pen will not be reliable, the sample tested will appear to be more acid than it really is.

Warning: Pen marks are not removable.