Is there any kind of hardener for cardboard?

Question

Does anyone know of a substance that could be painted on cardboard to harden/strengthen it? Preferably something that can go over paints. Please excuse my ignorance, but in the carpentry/hardware department, I know nothing.

Answer 1

You can use a polyurethane or any kind of clear sealer.... those would be found mostly in hardware stores, but art supply and craft/hobby stores will have various kinds of clear sealers too (often glossy).  Every additional coat of it  will make the cardboard stiffer, but you don't really say the size or type of cardboard you're using, and that could make a difference.

If you want something even stiffer, you can get the equivalent of many coats of polyurethane with an epoxy resin like Envirotex Lite --or for large areas, there's Glaze Coat (Famowood by Eclectic) available at Home Depot.  Epoxy resin comes in two bottles of equal size, which are mixed together then immediately brushed onto a surface, or poured onto it (elevated and allowed to run off the edges, or contained in some kind of dam).

More info and brands re epoxy resin are on this page if you're interested:

http://glassattic.com/polymer/other_mate...

You could also reinforce the cardboard in some other way... on the back, for example, if it wouldn't show.  You could use a backing layer of something stiff, or even with more cardboard (if using corrugated carboard, make sure the corrugations in the back layer run at right angles to the ones in the front layer), or with strips of things, etc.

Or you could reinforce it with papier mache, or chicken wire, etc.

HTH,

Diane B.