Someone I know recently had his tefillin checked. His tefillin are about 15 years old. The sofer who checked it said that the parshiyos were written with very thick ink, and as a result the ink was "breaking" along the folds of parshiyos shel rosh. He said while there was only one noticeable crack so far (which he repaired), he suggested changing the parshiyos, as they would always be high risk and susceptible to future cracking. The person contacted me and asked me if I had any good parshiyos I could sell him. When he told me why he was changing his parshiyos, I suggested to him that he not change the parshiyos but rather go over the bruised ink with dyo lonetzach. This would ensure the ink will not crack again. Ideally, even to touch all the parts of letters situated on the folds of the shel rosh parsha. This exercise takes no more than 20 minutes and is extremely effective. Even if the thick ink does crack with time, the letters will never become possul because the upper...