Shame on me, I did not make a 2nd round of pens for almost 18 months. The sheet of base wax my dentist had given me has gotten very stiff and sometimes breaks apart when pressing the end of a tube into it along an edge. An MSDS for base wax suggests it is primarily or solely paraffin (derived from petroleum). In theory mineral spirits will soften the base wax, but too much might make it too soft, and mineral spirits is so very slow to evaporate. Has anyone encountered this problem and found a solution?