I agree that all tape will leave some residue after being in place for a while and especially at high temperatures. I admit that i haven't tried leaving super 33+ in my pocket around a tin, but i have used it on antenna towers to wrap cable connectors and left exposed to sun and rain. The main thing is the nature of the residue: The cheap 25cent vinyl tape from china will immediately ooze a sticky clear goop that takes solvent to remove, the super 33+ will eventually dry a bit, leaving a dry black layer. You can sometimes get this off by sticking and peeling off some new tape, but solvent will do it too.

I would still favor electrical tape for sealing tins against water as it seems that the gaffers tape doesn't stretch and conform much because of the cloth inside. Might be a fun test to seal up some altoids tins with each kind and throw them in the pool. <img src="/images/graemlins/smile.gif" alt="" />