u/CartoonistSubject191

Hello, Im trying to build a transparent shelf with the dimensions of 31.375in x 13in. It will be supported with L-brackets from both short sides and a single middle support. The weight the shelf will hold will be 28lb in the worst case, spread mostly evenly across the length of the shelf.
I am not sure the exact material or thickness I should aim for. I don't want noticeable sag, but I don't want to overpay for the shelf either. Any insight? Is 1/8in acrylic too thin? Thanks.