Volume 4, Number 3
Jul 1991

Comparison of pH Pens on the Market--A Follow-up

In the November 1990 Alkaline Paper Advocate, we published the results of a survey of the various pH pens on the market. One of the suppliers, REL Graphic Systems, recently sent their new pen, the Paper pH Tester Pen, and it was decided to see how this pen compares with its supplier's claims.

The pen has a white barrel and green top, with the pen name and manufacturer (a firm in Belgium) printed on it. The barrel also has a well-presented and convenient color scale with the corresponding pH levels.

Method

As in the previous study, we drew a line with the pen on each of seven pH-buffered test papers and compared the results with the color chart on the pen.

Results

The pen contains an indicator or mix of indicators which makes a light mark on the test paper, an advantage when testing papers or books of value. The mark reached its color virtually instantly. The mark turned a pale peach shade at pH 4.0, began to change shades between 6.0 and 7.0 and eventually darkened to blue/gray at 10.0 (see table below).

Conclusions

The pen worked well but we encountered the same problem we had had with several of the pens in the November report: that is, the results did not match the supplier's predictions. Unfortunately, using the color chart printed on the pen, a user testing paper which actually had a pH of 7.0 would assume the pH was between 5.0 and 6.0, an important difference. For accuracy a color chart made up of papers with known pH's should be used.

The pen (also referred to by the supplier as the Litmus Pen) is available from REL Graphic Systems & Marketing Corp., 218 N. Clinton St., Chicago, IL 60606 (800/521-1080) and costs $24.95.

Color Comparison of Paper pH Tester Pen*

*Code numbers are from Pantone Color Formula Guide 747XR.