Using dollar-store picture glass for print bed on top of original heated aluminum bed? I'm having a really hard time printing on my aluminum heated bed... Cleaning it just results in it being scratched (trying to scrape dried hairspray/glue/etc off) and I don't think it is particularly flat either.

I was thinking of stopping by the dollar store on my way home and getting several picture frames and using the glass from them as interchangeable glass beds - this would also make it easier to take them off the printer to clean without needing to re-level the bed every time as the aluminum base would stay-put.

Do you guys think the quality of it would be okay to print on? (withstand the heat, be flat enough, etc) I'm planning to coat it in purple-glue-stick as I have heard that works well for adhesion purposes.

For reference: Printing PLA, Prusia i3 printer.
Picture frame glass (generally float glass) will work well enough, but count on it eventually cracking/getting chipped. It's always very flat (due to the way the production process works).

Taking it up to 100-110C for printing ABS should not be a problem, but you'll want to avoid sharp changes in temperature, and should be careful that your prints don't adhere too well: I've had PLA/PETG prints take out pieces of glass with them due to the force required to remove them from the build plate. You might want to try without any (or very little) adhesive first, and make sure your nozzle isn't too close to the build plate.