There is discussion on how to assess materials to avoid problems from static electricity. The limitations of ?resistivity? measurements and charge decay measurements using Federal Test Standard 101C Method 4046 are appreciated. The author has promoted the use of corona charge decay for a number of years. Two doubts have been raised about the practical value of making charge decay measurements using corona charging:

It is, of course, a possibility that corona could change the characteristics of materials. If a surface is damaged in a way relevant to changing its decay characteristics (other features such as colour are not directly relevant here) then one would expect that the modification would be less for a low corona exposure and greater with more exposure. Studies were reported at the 1995 Electrostatics Conference in York to examine just this point for the variety of materials [1]. Charge decay measurements were made with minimum corona exposure, followed by a high corona exposure followed by a low exposure. The results showed similar first to last behaviour ? indicating no significant modification of characteristics by the corona exposure levels used.

The comment on surface damage raises two questions:

1) Where is the evidence that the charge decay characteristics are changed by corona?

2) What evidence is available that resistivity measurements and tribocharging measurements do not modify surfaces?

A point needs to be considered regarding ?validation? of practical measurements to assess the suitability of materials to avoid problems from static electricity. In studies reported at the Electrostatics Conference in 1999 [2], at the IEEE -IAS meeting in Phoenix in 1999 [3] and at the ESA meeting in Niagara Falls [4] it was shown that the charge decay characteristics (and capacitance loading values) with corona charging are very comparable to those with tribocharging. This seems a reasonable way to validate charge decay measurements. Have any comparable studies been done for resistivity measurements, or for contact charge decay?