I always use a metal fingernail file to score the skinny part of the neck
before snapping the top off. Saw on one side fairly hard till you see its
got a good deep scratch. Then use a towel to keep from cutting your
fingers and snap the amp away from the scratched side. you'll get a clean
break every time.
I've often wondered- does anyone use a filter when pulling from a glass amp? I doubt it-- but I had read that in the medical field, doctors/nurses are supposed to use a filter to screen out tiny glass particles when administering drugs from ampules.
Not that much could fit through a 23g needle... but just curious.