Lineco pH Testing Pen for Paper or Paperboard Products.<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>pH Testing Pen</li><li>Determine whether paper or board is acidic</li><li>Simply draw a small line to use</li><li>Pen will turn purple if pH is 6.8 and above</li></ul></div><img src="http://ecx.images-amazon.com/images/I/41CJLjM90EL.jpg" noproxy>