Characteristics of erasable ball point pens

In 1979 shortly after the introduction of the erasable ball point pen two papers were published describing its basic characteristics (W.J. Flynn, J. Police Sci. Adm., 7 (1979) 346–349; P. Pfefferli and J. Mathyer, Rev. Int. Criminol. Police Tech., (1979) 407–419). Since that time two additional makes of pens and other colors of ink have been introduced, and the quality of writing has been significantly improved.The ink of the erasable pen differs significantly from that of the standard ball point pen, and for that matter from ink of all other modern day pens. In what way might this newer pen produce a written line different from other ball point pens? This is one question that the paper addresses with limited success.When erased, what techniques can be used to attempt to determine the text of the original writing? The writer considers all standard methods for deciphering erased writing and discusses modification by use of infrared film with oblique light photography — the method most successful in determining the original contents of the erasure.