This can happen when the nozzle is held in one position too long. This will cause the mask to heat up and soften, reducing its capabilities as a resist. A second possible cause is contamination in the grit. Contaminants act like a “dart,” piercing the mask and causing a pinhole effect. A third possible cause is the use of abrasive media that is too coarse. Photoresists are most effective when used with grit of a 180 mesh size or finer.
—IKONICS Imaging
