Reply To: Acid Test Pen, Folder test question


Hi Marybeth,  Carr McLean sells two different pens with different chemical solution.  The Abbey pen is for testing pH and contains chlorophenol red in the felt tip.  The groundwood test pen contains a corrosive/toxic acid – hydrochloric acid (muriatic) but works the same way in that a line drawn on paper sample to be tested changes colour in presence of groundwood pulp.