For those who build or want to build illusions like the ones in
Victory Carton Illusions
hamiltonholtinc.stores.yahoo.net/viccarilwrit.html
You can use Minwax High Performance Wood Hardener to strenghten Cardboard and cardstock soaked in the stuff become hard, rigid, and water resistant; the resulting material resembles phenolic plastic and can be sanded and machined with power tools.
makezine.com/pub/tool/Minwax_High_Performance_Wood_Hardener