Today I looked at a set of tefillin that had some kind of substance on the bottem of the shel rosh. It looks to me like a chatziztah (barier) between the shel rosh (head tefillin) and the wearer. The parshios were so tight in the battim that I couldn’t get them out. I will give them to my battim expert, Yehuda Meir Guttman who will take them out for me (in the secrecy of his office). The shel yad was so brittle and dry it cracked into two when I opened it.