It is possible to fight cardboard curl, buckle, or warp; plus make ordinary corrugated an archivally stable art material. Starting with a base coat of gesso will prepare the cardboard to better hold on to which ever type of paint you choose. Gesso will also slow acid from leeching through from the cardboard to alter your painting in the future, however gesso is brittle & can crack. A much better product to use as a base coat is clear acrylic gel medium. It's flexible, and it stops the acid in the paper from getting through at all; the acrylic polymers, in effect, create a seal. Liquitex makes an excellent heavy bodied gel medium that can be purchased at most craft & art supply stores, and because it's thick it doesn't warp as much as a base coat of gesso or paint. Oil paint won't adhere well to acrylic gel, so if you're using oil apply several layer of gesso after sealing with the gel medium.
Starting the center of the piece of cardboard, move a loaded brush of medium from top to bottom in a line; reloading as needed. Work swiftly. After applying an even line from top to bottom make another line on one side, then the other, of the first line. Allow the brush strokes blend, or feather, into the edge of the previous line to avoid building up texture that could show through your painting later. Work your way out to the edges, coating the piece evenly. Don't panic if it pulls up like a taco -- let it and don't push it down flat. When the first coat is dry, flip it over and coat the reverse in the same way. The taco curl should lay flat again as it dries because the tension on the surface of the material is even. After the back dries you'll probably want to do the front, then back, again before beginning your artwork. If it does warp while you're painting, keep the moisture level even by lightly misting the back with a spray bottle or re-coating.
If paint gets into the raw edges at any time then that paper corrugated on the inside can cause a warp. The solutions are to either avoid the edges altogether when painting or cover them with paper when base coating. With narrow strips of paper, and the gel medium, the cardboard can be perfectly sealed; acrylic gel medium has the added bonus of acting as an excellent glue! Just one fourth of an inch overlap one each side of the cardboard should be enough coverage. Be sure to "paint" the gel medium all over the strips, and if they slide, use less gel on the brush. Then coat them better after the first layer dries. The raised line of the paper strips will most likely be covered by a frame when the painting is finished. Keep the strips even and you'll have a nice clean edge.
Unless exposed to very high humidity, or moisture, the piece of cardboard should now remain flat. Very large thin pieces may need some support that can be achieved with a frame and backing board. Covering the raw edges of the corrugated cardboard creates a seal that stops air or moisture from getting inside. Decay from acid oxidation is stopped, making a surface for art work that is archival, ready to be enjoyed for many years to come.
|Timber Land Steam Stack|
Shown at left is a painting assemblage where the same method was used, but with a full sized sheet of paper covered foamboard. As can be seen by the drips and running of the paint, I worked this very wet. This piece, a scene from the Pacific Northwest in my private collection, is several years old now and remains flat in the frame despite not having rear backing support. Titled "Timber Land Steam Stack", the curling form of a steam cloud is created from a recycled bent wood coat rack with cut out silhouettes of plastic coffee can lid ravens that free float from monofilament. Some of the ravens are adhered to the painting with acrylic gel medium. The bits of wood are wired to the foamboard, and so do provide a bit of rigid support. Coating and sealing the edges, however, is what prevents the foamboard from warping.
Explore and have fun! -- Tree
*Original art images ©Tree Pruitt, unless otherwise indicated. Contact the artist prior to ANY use or for purchase information.