Area Lamp - Part 1
Posted 12.17.2018 by Mario & Kitty Costello
Kitty and I had talked for a long time about buying an Arco Lamp for our living room. It's a unique, timeless design by Achille Castiglioni that allows you to add some overhead illumination to a larger space, like a dining room or living room, without having to go through the trouble of anchoring something into the ceiling and then running wires to it. For various reasons we never got around to tracking one down and eventually decided that maybe it presented a good opportunity to design and make our own version. The overall shape of the original presented a good template to work from, but we would deviate and add our own touches here and there to suit our living space, our budget and the fabrication tools and processes available to us.
The original base for the lamp, which provides the mass that anchors it to the floor, is a piece of Carrara marble measuring 7" W x 9" D x 21.5" H and weighing about 140 lbs. Since there was no economical way for us to get a piece of nice stone cut to similar dimensions and we had always wanted to learn more about molding concrete, we decided this would be a good opportunity to dive in and learn something new about a material we were unfamiliar with. We had a pair of aluminum prototype lamps in our living room from a previous project and decided that we would roughly mimic the same body shape in the base of the new design, which is basically an upright rectangle with rounded corners.
The long, graceful extension arm of the lamp imparts quite a mechanical moment on the assembly, so getting the footprint and the weight of our version would be important to making sure the whole thing didn't tip over, especially since we were considering making the extension arm out of a heavier material than the original Arco (1" brass square tube with a 1/16" wall) and extending it an extra foot into space. Marble is much denser than concrete, marble being about 170 pounds per square foot to concrete’s 100 to 150 pounds per square foot depending on how it is mixed and compacted, meaning we would need a larger volume to achieve an equal weight. Since we also wanted to increase the footprint of the base (W” x D") to make the lamp more stable, this wouldn't be an issue. And, since the overall dimensions of our lamp were a bit bigger than the original Arco, the larger size of our base would scale properly in relation to the larger assembly.
The concrete would allow us to mold threaded metal inserts into the base to attach other parts of the assembly like the extension arm that holds the shade and the feet that would contact the floor. These would be nested within the mold form and then then the concrete would be filled in around them. Also, we could easily add internal routing for the wires, which is possible with a block of stone, but vastly more difficult and expensive.
Finally, there is a lot of flexibility with concrete in terms of deciding on its finished appearance. It can be dyed various colors using powdered pigments and liquid dyes. The content of the concrete can be augmented by adding additional media, like different types of small stones and crushed glass that has been polished in a tumbler, which gives it an appearance similar to terrazzo flooring. And, finally, the tactile feel of the surface can be left a rough matte or polished to a fine, reflective surface. When you’re starting a project with a material you know very little about, it’s a good idea to do a bit of reading and then experiment to learn the basics, which will be covered in the second blog post in this series about designing and building our own area lamp.