I'm tellin' ya bro, try the mirror. You don't lose one bit, it's all easily scraped up with a razor. Besides, the chance of getting any bits of cardboard in the bubble sucks.
I also froze mine, but I need to explain: When I was making bubble, I used a DIY bubble bucket set. That allowed me to take the screen off with the bubble still in it (the 73u was normally the best screen for the strains I ran at the time). I collected all the bubble into a corner, dabbed the majority of the moisture off with a towel, and put the folded screen into the freezer. After about 10 minutes, I'd pull out the screen, carefully unfold it, and pop the frozen hash off onto a mirror.
A touch bit of moisture actually helped to get the hash off all in one frozen piece, so long as I collected all the trichs together well in a corner. (I would fold the screen in a certain way, that would allow most of them to pool together nicely. Any stragglers would be gently moved towards the pile with a water squirt bottle.)
I also froze mine, but I need to explain: When I was making bubble, I used a DIY bubble bucket set. That allowed me to take the screen off with the bubble still in it (the 73u was normally the best screen for the strains I ran at the time). I collected all the bubble into a corner, dabbed the majority of the moisture off with a towel, and put the folded screen into the freezer. After about 10 minutes, I'd pull out the screen, carefully unfold it, and pop the frozen hash off onto a mirror.
A touch bit of moisture actually helped to get the hash off all in one frozen piece, so long as I collected all the trichs together well in a corner. (I would fold the screen in a certain way, that would allow most of them to pool together nicely. Any stragglers would be gently moved towards the pile with a water squirt bottle.)