I didn't buy the tap and glue caps. I asked your question here a couple of
years ago, and I didn't hear too many favorable things about them.
My elmer's glue tops held up pretty well because I give the kids a big song and
dance about "glue surgery" (any attempt to unclog a bottle with scissors,
pencils, fingernails or teeth) and how they must never try it on my glue
bottles. I take a partly used bottle of glue, twist it open, and while it is
upright, have them listen to the sound as I squeeze it. I tell them that if
they hear the air going in and out, the glue bottle is breathing and it will
work fine. If they find one that isn't breathing, they better raise their had
and ask for the "glue doctor" (me) to come give it a check-up. I've been to
glue medical school, so I'm the only one in the room qualified to do surgery on
a glue bottle. So the students don't tear up the tops.
The biggest problem I had with glue is the tops being left open, because those
are the ones that won't be breathing next time we need them. For that I guess
I needed to assign a student glue checker.
As far as over usage/underusage of glue goes, well, we all learned to say "dot
dot not a lot" in kinder, but that is hard to live by. I still see a lot of
glue scribbling or collage art where the edges didn't get glued, so pieces are
flapping. Maybe another song and dance?