Paper is a useful and popular craft material for many reasons. Construction paper comes in a variety of bright colors. Paper is also easy to cut, fold and attach other materials to. However, sometimes paper's natural flexibility can be a problem. There are several ways to harden paper to make it into a more rigid object or surface.
The classic craft process of papier-mâché is one way to harden paper. You can choose to blend your paper into a papier-mâché mixture, or apply papier-mâché lightly to the surface of paper, which will cause the sheet to harden once the papier-mâché dries. Papier-mâché, in its most basic form, consists of water, flour and paper. The paper becomes saturated with the paste-like flour mixture and becomes very hard once it dries.
General-purpose paste will cause paper to become more rigid. Make sure that you apply a very thin layer, because water-based paste or glue can saturate some papers or cause others to curl as it dries. To prevent curling, use heavy tape (such as masking tape) to attach a piece of paper to a flat, hard surface on all four sides. Apply paste or glue over the paper and wait for it to dry. Then remove the tape (you may have to cut it away) to release the hardened paper.
Artists use workable fixative to protect layers of charcoal, pastel or pencil work on paper and other surfaces. It comes as an aerosol that produces a fine mist, which dries within a few minutes. When applied to paper, with or without artwork on its surface, workable fixative will stiffen the paper and give it a textured surface. Multiple layers will make the paper even more rigid, while allowing you to continue to paint or draw on the surface.
Hairspray serves much the same purpose as workable fixative, though it produces a surface that's more difficult to paint or draw on. Most aerosol or pump hairsprays will cause paper to become slightly rigid within a few minutes. More layers will increase the effect.