Although it is quite common in Canada and the USA to use ink pens for testing treatment level of films, it has been proven time and time again that this testing procedure is not accurate. As these pens have a tendency to lose solvent (formamide and ethyl cellosolve mixture) through evaporation due to poor fitting caps, the concentrations and hence dyne levels of the pens change.

Also, cotton swabs should not be used. It has been shown that different cotton swab manufacturers use different binding materials to attach the cotton to the stick and this can affect the test solution and hence the results. The pressure used on the cotton swab can also dramatically affect results.