Bent Cardboard

Me and cardboard furniture go way back. I built my first series of cardboard chairs for my freshman design studio, a decade ago this fall. I made three, each relying on a system of intersecting grids to support the seat. The next two years I also made cardboard chairs, entering them in the Chair Affair, a competition sponsored by the American Institute of Architecture Students. I made a stool from Fed-Ex mailing tubes, with a woven seat, and a cantilever chair, combining corrugated material with laser-cut chipboard and cardboard tubes. 
The FedEx stool, one of my first (and ugliest) attempts at cardboard furniture.
All five of these efforts were rather clumsy, each in their own way. They were some of my first chairs, and each was less than ergonomically ideal, suffering from a wide range of dimensions as I cast around for a set of good proportions. None of them were terribly durable, although two survive to this day, albeit with intermittent use. Aesthetically, I'm not thrilled with any of them, and only show photos here as a window to the process.

Another early effort, covered in a really ineptly applied, wrinkly-ass coat of paper-mache.

Cardboard is a great material for the guerilla designer. It is free, plentiful, and easy to work with minimal tools. It can be laminated with wheat paste, which costs cents on the gallon to make. These factors combine to create a low cost for failure, making cardboard the ideal medium for experimentation.

There are three main methods for making a cardboard structure that will support weight: intersecting grids, folding, and lamination. Each method is dependent on a careful manipulation of the grain, or direction of the flutes, in the sheets of material. Cardboard can bear a remarkable amount of weight when loaded directly in line with the flutes and kept from buckling side-to-side. 

Intersecting grids, like the simple structures found inside a twelve-pack of beer, orient the grain vertically and prevent buckling by bracing each sheet with a regular pattern of perpendicular sheets. Folding uses origami-type techniques to crease and bend sheets back on themselves, creating (usually) triangular cross-sections that resist deflection. Lamination typically pastes together hundreds of sheets of cardboard, all with the grain running vertically, creating a mega-block of mass that acts much like lumber. 

My cardboard cantilever series worked on that principle: a big enough mass will support a person, even if a significant amount of it is carved away. The first two worked well enough, but lacked the grace and visual lightness suggested by a cantilevered form. They were bulky, heavy, and ugly. 

My first cantilever used different types of cardboard in five distinct layers, knitted at the vertices with cardboard tubes.

This one used threaded rods to hold the layers together, and a healthy layer of paper-mache, which turned it particularly bulky and ugly. The photograph isn't helping things, but it was recovered from a lost hard drive, so my apologies.
My third cantilever worked better. I systemized the construction with a jig and a table saw, and got the structure as thin as I could manage. That said, the thing eventually sagged and slowly collapsed. The knee joint failed, as I had no continuous plies, just short strips that overlapped at each joint. 

The jig. A top plate (in the background) fit onto the threaded rods in each corner, allowing me to crank down on the layers so they would dry under considerable pressure.
It worked well for about six months. Then I planted them in the garden, seeding them with grass to die a natural death.
For months now, I've been thinking about a new type of cardboard lamination. Everyone's mid-century heroes, Charles and Ray Eames, figured out how to mold thin veneers of wood into compound curves using heat, pressure, and new types of adhesive. I thought I might press layers of corrugated cardboard in a curved mold, with copious amounts of wheat paste, hoping to produce a rigid, stable, and torsionally stiff shell that is ergonomically correct, materially efficient, and handsome.

Well, it worked! It doesn't look like much, but I've produced one panel so far, about 16" square, with masonite buried in the edges so it will hold screws effectively. Check back over the next few weeks to see how more panels turn out and whether or not I can crack the frame problem. Suggestions welcome.

Wheatpastin'. Used whole wheat flour because it has more gluten, increasing strength.

I made a simple machine to determine the curve for the mold and eventual panel. A 48" string, tied to a screw at one end and a pencil at the other, is used like a giant compass to strike a portion of a four-foot radius onto a 2" x 4".


Cut on the bandsaw.

Once cut, I clamped the pieces together and sanded them to make them uniform.

Mold frame taking shape.

1/8" Masonite added as the skin.


Ready for lamination.
The stack of panels, wetted with glue and ready for compression. Each piece of cardboard is alternated, grain-wise, so the flutes run perpendicular to one another, just as the grain of the veneers in plywood is alternated.

Under compression.
Raw out of the mold after 48 hours.
After a run-in with the table saw.

Close-up. Note masonite at edges, for accepting fasteners.