How to Harden Paper Bags

Whether you want to stiffen some old-fashioned brown paper for use in an art project or reinforce a paper bag for the sake of carrying something that needs extra protection, you can harden paper bags yourself using a glue solution. This technique will allow you to leave a certain degree of flexibility in the paper or harden it to a higher degree, depending on your needs.

Mix a glue solution of one part glue to two parts water. Stir the mixture with a fork until the glue is evenly distributed in the water. Use extra water if the glue you have is unusually thick.

Unfold the paper bag and stand it up. If you need to protect your work station from glue solution, lay down a few coats of newspaper under the bag, as this will get messy.

Give the bag a light coat of glue on the outside using a sponge brush. Let dry for a few hours or until the surface is dry to the touch. As the glue dries, monitor the bag to make sure that it doesn't sag or re-fold itself from the weight of the liquid, since it will permanently keep its folded shape it if does.

Coat the inside of the bag in glue. Cover the paper just in solution and let it dry just as you did with the outside. As the inside is coated and dries, watch for excess solution pooling in the bottom of the bag and soak it up with a rag; if too much gathers, it will soak through the bottom of the bag and glue it to what's beneath it.

Repeat steps 3 and 4 until the bag is as hard as you want it to be. One or two coats of glue will make the bag firmer and stiffer, but not inflexible. More coats of glue will make the bag completely hard.

Flip the bag over and coat the bottom with glue. Use more layers of glue on the bottom than you did with the rest of the bag in order to make it stronger.