Hi, I have an old Parker squeeze converter which at first sight seems to work well, holds a lot of ink and is not leaking. However when I squeeze it the rubber has some cracks in one part , the rubber is not yet cracked completely but sooner or later it will. I can still use it and it also feels flexible. I was thinking if there is any preventing work or something. Can I melt the rubber with the hot red point of a needle so the crack is no longer spreading ? Or can I glue it somehow? Thank you!