Term of the Week: Viscosity

Joe Clarke has spent the past 47 years in the lab and in the engineering department, in pre-press and on-press, as an R&D / technical researcher and as a manager of screen print production. Clarke has held executive positions as President of M&R Printing Equipment and as Vice-President at Wilflex [Poly One]. He has been granted a growing number of print-related patents, including one for High-Shear printing with Smilin'Jack - he is a member of the ASDPT, is an Associate Editor for NBM and an SGIA Fellow.

Clarke has presented hundreds of technical papers, written a couple books and published over 600 technical / management articles for which he has been awarded five Swormstedts; the international standard for excellence in technical writing.

Currently Joe Clarke is the President of CPR, a Chicago-based corporation which manufactures Synergy Inks including NexGen; environmentally & financially responsible T-Shirt inks. For more information on CPR, visit

Viscosity refers to the measure of the resistance of a fluid (in our case, ink) to flow. Absolute viscosity refers to the ink at its highest relevant point—when it is flooded on top of the mesh. The same ink changes its viscosity (called plastic viscosity) when it is put under a shearing-force, i.e. when it is pushed by a squeegee at a certain speed. Quality inks are extremely shear thinning, tacky inks are not.