Need help with making shelves work, please.?

Question

I have these ugly plastic shelves and where you lay things, is like lattic, with holes. I decided to cut something to fill the space and make more attractive and functional. I bought 1/4" plywood - cut into 17" x 35" - fits in there perfectly - but of course, I didn't think about how it would bow.

I'm thinking of stain/polyeuthene and forcing it flat while it dries... any chance this will work or do you have any other suggestions to keep them flat.

Can't connect, glue, or nail it in any way due to the way these plastic shelves are build.

Answer 1

Can you not bolt through the lattice and the ply with small machine screws, perhaps with large penny washers on the lattice side to hold it flat to the grille? Alternatively tie or lace it on with invisible nylon line?  If you put enough stuff on it of course gravity will do the rest.

EDIT

Bit baffled - if the ply is being supported it must be in contact somewhere - even if you hold it with double sided tape where this happens it might be enough. Apologies if I am getting hod of the wrong end of the stick. Another option might be a narrow batten either as a lipping to the front edge or an upstand at the back - glue and pin (nail) to the board to persuade it to stay flat.  If ever daced with this again glass, perspex or MDF might be better alternatives. The rule with plywood btw is what you do to one side you must do to the other, if you are to avoid it going like a banana.

Answer 2

I think your mistake was in using plywood.  You can get nice pine or birch boards that will remain flat once you paint/stain them.  If you live near a lumber yard, maybe you can order a nicer grain of wood, like mahogany or walnut for your shelves....although it will probably cost more than the shelves did in the first place.

Maybe some plexiglass sheets cut to fit?