Cement Sculpture Technique
Creating a large outdoor cement sculpture requires time patience and physical stamina.
The first step is to sketch out your ideas but also remain flexible to allow for some needed changes while you are executing your design. Changes might be needed for physical or visual balance or you may just not like the direction the piece is taking and you might have inspiration in another direction.
You don’t want your piece to be too heavy but if you are able to work right on site it won’t matter as much. In order to keep it a bit lighter you will build your armature largely with Styrofoam and chicken wire and diamond lathe that is used in concrete structures.
Free Styrofoam is pretty easy to collect from dumpsters and trash cans and neighbors so keep you eyes open for big pieces on the curbs on trash day. If you want you can go buy big thick pieces at the hardware store. I personally always snag big pieces from neighbors whenever I see it. It doesn’t matter what the configuration.
Cut and glue chunks of Styrofoam together to form the core of your sculpture. Try to carve it into a rough shape that will approximate the shape of your finished piece. Make sure that the shape is physically balanced or you can anchor it with reinforcement bar (rebar) shoved through the center and into the ground if you are working on site. This would be the approach if you do indeed want your sculpture to be off balance. Keep in mind that you will be adding layers of wire and cement so keep the core smaller than you are expecting your finished piece to be. This is a matter of experience and trial and error. You can always add more layers of wire and cement but it is harder to reduce the size once your cement begins to cure.
Once your core is all built cover it with chicken wire pinning the chicken wire to the Styrofoam as you go. Don’t try to cover it all with one continuous sheet but rather cut pieces as you go and form fit it to the core. This layer of wire is basically to give more structure and security to the foam core. You will want to bend the little ends of the wire around and through each other and make it as secure as you can.
Next add the concrete lathe or diamond lathe over top of the chicken wire.
The reason you want to use the diamond lathe is that it will actually grab and hold the cement as you trowel it on.
This lathe is sharp and will tear up your hands so be sure to wear protection on your hands. Leather work gloves are a good choice. Again cut and fit and wire it in to your armature.
Your armature is important and really should approximate the size and shape of your finished piece. However, you can adjust and add to your armature as you go as necessary or as you desire. I have made significant changes in the middle of a sculpture making additions with more Styrofoam and wire.
Mix up your cement. I like white Portland Cement mixed with a white silica sand. The portions will be roughly one part cement and two parts sand and some acrylic binder mixed in with the water that I will be using to mix the cement.
Cement is mixed by adding water to the dry ingredients and NOT the other way around ever. Plaster is the opposite. The least amount of water should be used to achieve the consistency you need for troweling. Keep in mind that cement cures rather than dries. The best environment for curing is a moist one. Work with small buckets at a time as you will likely be working over a period of days if not weeks.
Begin at the bottom of your armature and trowel on the cement over the lathe. Work from the bottom up toweling on layers as you go. When you get to a point where you have to stop, mist the surface with a very light spray of water and cover the entire surface with painter’s plastic securing it with tape or cord. The next work session just begin again where you left off. You may want to spread a little binder on the cement that you have finished previously. You should also be able to work with rasps on the surface while it is still a bit moist. Cement gets harder with age so the sooner the better when carving or using rasps.
Since I am a sculptor and not a contractor or builder my technique will likely not be suitable for walls and structures. I would however love input and feedback from those in the building trades!
Pictures from my show "States of Being" 1999 Metropolitan State College of Denver