Set designers discovered the advantages of using spray foam long ago. Spray foam, which is a polyurethane based foam, is well-suited for making props because is lightweight, expands to cover large surfaces quickly, and is easy to carve and sculpt. Take a cue from set designers to make your own spray foam tree. With a bit of artistry, it is possible with spray foam to make any size or style tree you desire.
Create a basic armature. Cut a round piece of plywood for the base using a jigsaw. Cut it to the size you want the trunk of your tree to be. Cut a 2-by-2 board to the height you want your tree. Screw the 2-by-2 board to the centre of the plywood circle.
Cut a section of chicken wire with wire cutters and wrap it around the 2-by-2 for the trunk. Bend and model the chicken wire to form the shape of a trunk.
Cut several smaller sections of chicken wire and wrap them into tubes for branches. Hook and wire the branches to the trunk and bend and shape them as needed.
Prepare to apply foam. Put on gloves and mask and work in a well-ventilated environment. Spray foam is vaporous and very difficult to remove from your skin.
Start spraying the foam at the base of the tree and work your way up in a spiralling manner. Continue until the entire tree is covered. Leave the foam to cure.
Carve the foam as desired to smooth down the bumps in the foam and to create the surface texture of the tree. A knife, a rasp and sandpaper are all suitable tools for carving foam. Wear a dust mask when sanding to avoid inhalation of sanding dust.
Brush the tree with a hand broom and wipe it down with a damp cloth to remove all residual sanding dust.
Paint the tree with a plastic primer. Do not use aerosol or solvent-based paints, as they will dissolve the foam.
Paint the tree with shades of brown acrylic paint.
Add leaves to the tree, if you wish. Add leaves by poking holes in the foam with a nail, dipping the stems of fake leaves into glue and sticking them into the holes.