I recently used some orabond banner tape for hemming. Wasn't real impressed and it only stuck for a week or so even though I burnished the bejesus out of it... Anyone have a favorite?...
Did you bother to remove the backing tape? I've been using whatever Oracal calls their banner tap for lo these many years. It's never, as in ever, failed. Ergo it functions just as well as anything else on the market.
Perhaps there's something about your technique that could use improvement. Here's how it's done in this shop...
First mark the back of the banner 2" in for the edge all the way around. We use a 2" wide 4', 6', or 8' aluminum rule.
Do each edge in this order: bottom, sides, top.
For each edge apply the tape to the edge of the banner.
Before you remove the backing tape run down the tape with a squeegee; hard. You want to see an impression of the banner material in the backing tape.
Remove the backing tape and, assuming you're right handed, starting at the right end on the edge you're doing, fold the edge in to the mark you made. Using a brayer, start folding a rolling the edge. Roll along the hem and just slightly up yielding a bit of air egress. You can't apply too much pressure. The trick is you hold the edge sort of like you're rolling a huge cigarette. Get rid of any perturbations in the way the banner lies such that you can hold that U shape that neatly folds over all the way to the end.
Once the hem is folded, the run over it with a squeegee paying particular attention to the edge [i.e. the fold].