Take a cardstock paper. Use push pins at each corner to secure it down to a hard surface, like a cork board. You will first want to spray the paper with heavy spray starch, the kind you use for laundry. This way it will be extra hard. After spraying the heavy spray starch, wait 30 minutes then turn the paper over and spray it on the other side. Wait another 30 minutes and then apply the decoupage to one side of the paper. You can apply it with a brush or sponge. Let it dry for 1 hour, then turn it over and apply the decoupage to the other side. Let it dry for another hour, and then compress between two heavy objects or bucks like cookbooks for 24 hours to make sure it doesn’t wrinkle. Now your cardstock is hard and glossy, and ready to use for your craft.

Using Acrylic Varnish

A great way to harden cardstock or paper that has already been formed into a paper craft is with acrylic varnish. The best medium to use is spray varnish, which is quick-drying and waterproof and will protect your craft. It will also help to get into any hard-to-reach spaces which liquid varnish could not get to. Buy the acrylic varnish of your choice and follow the instructions on the bottle. The best way to do it is to spray your craft with a few coats and then let dry for 30 minutes. If you need to spray it again go ahead and do so liberally. The great thing about spray acrylic varnish is it will not make your craft ink run whereas other liquid methods might cause the ink to run.

Spray Starch

Stiffening paper with spray starch is a good idea because it is an item that you probably already have in your house if you use starch in your laundry. You can use liquid starch using a paint brush or sponge or you can use a spray version if you have that on hand. To stiffen cardstock with spray starch simply coat the paper on one side then flip it over and do the other side. The thing about spray starch is it only gives a light to medium hardness which is good for crafts that don’t need to be so stiff.

Minwax Wood Hardener

Minwax wood hardener is a spray used to reinforce rotting wood. You can use this to make paper really hard like wood or plastic. But be warned, this product needs to be used in a well ventilated area and with a mask as it is dangerous to breathe in. You can also use other types of wood hardeners or glue. Just brush it onto the paper and let it dry.

Fibreglass Resin

A great way to get the look and hardness of plastic is by using fiberglass resin. Considering that fiberglass resin is used in the manufacturing of cars, boats and even shower stalls it should tell you how hard this substance really is. You can find this product online, and all it takes is a few coats of the resin to harden the paper considerably. The good thing about it is that it is easily brushable and slow drying so you can apply a few coats at once. It will make the paper as hard as plastic.

PVA Primer

PVA primer is used to seal holes in drywell and protect it from moisture. Using a PVA primer is a great way to harden paper. If you are using the liquid version, thin it out first with some water, otherwise you can use it in spray form. It gives the paper a protective shield and makes it extremely hard. Don’t use too many coats otherwise the paper will be wet and wrinkly.

Textile Hardener

Powertex is a brand of textile hardener that is used to stiffen materials used in sculpting, such as paper, fabric, cardboard, leather, and fiberglass. Simply coat the paper or papercraft in Powertex and let it dry. Do note that Powertex comes in a black/brown color which may not work for what you are doing. There is a clear version which is not weatherproof.

Wood Glue

Wood glue is something you may already have in your tool chest. Dilute the glue with water and apply to paper or cardstock. You can create the shape or design that you want while the paper is still wet, then let it set and dry. Once it is dry you can apply a few more coats to make it extra hard.

Regular School Glue

The best thing about school glue is that it is something almost everyone already has in their home. You’ll want to create a mixture that is part glue and part water. For stiffer paper use more glue and less water, and for more pliable paper use less glue and more water. You can use a paintbrush to apply as many coats as you need, and more once it dries if it is not stiff enough.

Glutinous Wheat Paste

Similar to glue, you can make your own homemade gluten paste. You’ll need 2 cups of water, 4 tablespoons of flour, a pinch of salt, a saucepan, wire whisk and a craft brush. Bring the water to a boil in the saucepan on the stove and add the salt. Bring down to medium heat and add the flour a little at a time whisking well. Once all the flour is added you’ll begin to see a gel like substance forming. Remove from heat and let cool. It should be thick like pudding. Once cool, if it’s too thick add water, otherwise you can shape your paper into whatever you like and then apply the paste. The paper will be too hard to work with after the paste has dried. Let dry 2-4 hours and apply more coats as needed.