I picked up a cheek-pinchingly cute little etui of these Slime brand
"Scabs" when I was at the soul robbing Superduper Megamart last week.
$1.50. Worth every penny for scientific purposes.
I was not going to rely on these when on the road, but fortunately, I
picked up two Trek path bikes for $50 on craigslist, one with a
punctured front tube. Took them home, put on my lab coat and monacle
and pulled the front tube. It was a 3mm tear, likely due to a lousy
tube, not a puncture. In a clean kitchen, at a dry 80F, I prepped the
area with emery paper, not the crappy scratcher included, applied the
patch, and rolled it with a rolling pin. Perfect conditions.
I reinstalled it, and as I was hopped up on iced tea, managed to put
another hole in the tube from pinching it with the lever! Wonderful,
another test case. So I put on another patch, allowing both to "cure"
a couple hours, reinstalled, pumped to 40psi, and watched the tire
deflate in a couple minutes. Both patches failed. The glue was simply
too gooey. I pumped the tube outside the tire and you could readily
see the air creep through the adhesive till the bubble popped out the
edge.
No surprise, eh?