Recycled Cardboard Painting Surface

This project will give you a rundown on how to prepare a recycled corrugated cardboard painting panel. Of course, you can just paint straight onto cardboard if you want to, but this project will show you some steps to take that will make your cardboard "canvas" more archival and sturdy, which is important if you don't want your artwork to deteriorate over time.

Cardboard, recycled from delivery boxes

Utility knife

Steel ruler or straightedge

Sealant (this project uses shellac sealant made up from shellac flakes and methylated spirits/denatured ethanol, but you can use any type of sealant that you have; I like shellac because it's easily accessible and does not contain plastics)

Old paintbrush to apply sealant

Gesso

Wide paintbrush to apply gesso

Waxed paper

Fine grit sandpaper

Weights or heavy books

Shellac, also known as French Polish, is a natural sealant. The flakes are made from resin deposits made by lac beetles on tree branches. These flakes are scraped off the branches and can be dissolved in methylated spirits (denatured ethanol) to make a liquid sealant. As the methylated spirits evaporates, the shellac dries into a thin film of resin on your surface.

To mix a shellac sealant, add few spoonfuls of shellac flakes to an old glass jar and pour enough methylated spirits in to cover the flakes. Leave these for a while until the flakes have dissolved.

Sealing the cardboard is an important step. Cheap cardboard contains natural acid that will gradually eat away at your painting over time. Adding a layer of sealant helps protect your painting from that acid. It also works the other way; stopping oils and ingredients in your paint seeping into the cardboard and destroying it. Gesso alone isn't enough of a protective layer, which is where the sealant comes in.

It's good practice to prepare all your painting surfaces properly, particularly if you're selling your original artwork.

I paint two to three layers of shellac sealant on both sides of my cardboard, leaving them to dry between each layer. Shellac dries very quickly, so if you choose this type of sealant, you don't need to wait for a long time between coats.

To easily paint your shellac all the way up to the edge of the cardboard, sit the cardboard atop a smaller item to lift it off your table. Don't forget to put a piece of scrap paper or drop sheet over your table top to protect it from spills.

If you're using shellac sealant, you can clean your brush with methylated spirits when you're done with this step.

When the sealant is dry, it's time to prime your cardboard with gesso.

I'm often asked if people can just use white paint instead of gesso. The simple answer is no. Gesso looks like white paint, but it's actually a specific formulation of chalk, binder and pigment. The chalk in the gesso creates a receptive surface for your paint. The chalk grit helps your paint stick properly to the surface.

The most common colour for gesso is white, but you can mix in other pigments or paints if you want a different colour for your base.

If you're painting with acrylic paints, you'll need at least two coats of gesso.

If you're painting with oils, you'll need to apply at least four layers of gesso.

Sand your gessoed surface lightly with fine grit sandpaper between coats, and paint each layer of gesso with strokes in the opposite direction from the previous layer, allowing each coat to dry fully before apply the next one.

The thing with cardboard is it doesn't like to get wet, and the thing with corrugated cardboard is that it bends, especially when wet.

I started out priming panels that were the size of a standard piece of printer paper, and after sealing cardboard that was only a single layer thick, I noticed that it was warping. I ran some tests to figure out how to prevent this. Sticking two layers of cardboard together, with their corrugations running in opposite directions, worked fairly well, but when I painted on this surface I still experienced a degree of bowing.

If you want to make larger paintings on cardboard, I'd recommend attaching some sort of back brace like you see on bigger canvases to help keep the surface flat.

The next step I took to help prevent the panels warping was to make them smaller. I quartered my sheets and glued two pieces of cardboard together with the corrugations running in opposite directions, and the smoother sides of the cardboard facing out.

When I'd stuck a number of the small panels together, I wrapped each one in a piece of waxed kitchen paper and stacked them on top of one another, then placed some heavy books and weights on top. The weights help keep everything flat as the panels dry, and the waxed paper stops the panels from sticking together under the pressure of the weights.

After leaving the panels overnight to dry, I was able to unstack and prime them using the same methods previously mentioned. The smaller size panels came out very well, and have not showed any signs of warping or bending when painting.

If I do have problems with warping in the future, my plan is to lightly dampen the reverse side of a painting with a spray bottle of water when it's dry, then leave it under a stack of books/weights to flatten out.