Are pH Pen Tests Reliable?
Courtesy of FACTS
User testing of pH with a pen can lead to misunderstandings and general confusion between manufacturer and customer. Checking pH levels by marking a line across the paper and reading color is not always a true reading of the actual pH of the paper.
Many surface coatings or treatments used on paper to improve its runability can be misleading to simple pen tests. These coatings which are many times undetectable to the eye or hand and which may be higher or lower in pH than the paper it is applied to lead to unreliable pen testing.
Several discrepancies of this type have occurred during the past year. A good alkaline paper treated with a coating for runability, thought of as an improvement by the paper supplier and the manufacturer, tested in the field with the pen are immediately thought of as acidic materials when in truth it was only a coating.
To determine whether a paper is actually alkaline you must accept the alternatives described in the ANSI standard for paper permanence, Z39.48-1992. Either tear the paper to expose the inner surface, and do a spot test with a pH indicator such as chlorophenol red, or accept the manufacturer's certification that the core paper is alkaline and was made at an alkaline pH.
The use of a pH pen to test new incoming papers should only be used to check and any discrepancies should be checked with the manufacturer or supplier. There is no reason for a manufacturer or supplier to misrepresent their products as to the pH or archival qualities.
