Arcosanti Silt-Casting Process

Arcosanti Silt-Casting Process

A short film by Ana Catalina about The Cosanti Foundation's unique silt-cast process used by artisans at Arcosanti for over 50 years to make their renowned ceramic bells. Additional music provided by Jaden Chavez.

Arcosanti Silt-Casting Process & Basics

a conversation with Ana Catalina

The Materials

There are three main elements used in slip casting: silt, slip, and water.

We source the silt from the Agua Fria River, which runs through our property at Arcosanti. Silt is a sediment that is made up of very fine sand with a percentage of clay, which allows it to hold its form and be a good mold for our bells. Because we take good care of our silt, the same batch can last us for many years.

Slip is just clay mixed with water into a milkshake-like consistency.

Water is just water.

Photo by: Shanta Ambady

The Ceramics Apse at Arcosanti

An apse is a quarter of a sphere. The ceramics apse, which houses our ceramic’s studio at Arcosanti, was designed to work with the changing sun angles throughout the seasons, so that we can work outdoors year-round. Having an outdoor studio means that our production is very in-tune with the cycles of nature.

For example, in the winter when it's moist and the sun isn’t out every day, the clay dries more slowly and our whole process slows down. During this time we can catch up on other smaller  but necessary tasks, such as building up stock of the smaller pieces used in the assembly of our bells. By contrast, in the summer the clay dries very fast and our overall production speeds up. For example, a silt-casted bell in the summer can be ready to come out of the mold the same day it’s poured, while in the winter it can take up to a week, so it’s a big difference.

Photo by: Jeff Shewmon

The Process: Next Steps

After we take the bells out of the molds, we rinse them off with water to get the excess silt off of them. A thin layer of silt remains, which gives the silt-casted bells their unique texture and color.

After that, we set them out in the sun to dry until they harden just enough to hold their shape when handled.

Then, we clean up the edges of the bell with a paring knife and a sponge, and pierce a small hole at the top to be able to assemble it once fired.

Next, we powder them with oxide powders and let them sit until they reach a leather-hard consistency. Once they reach this consistency, we carve designs onto them using utility knives. The oxide powders not only give the bells a beautiful earthy tone but they also help the carving stand out more.

After carving, we let the bells dry completely to what is called “bone dry”, we fire them in our electric kilns, and assemble them.

The Products

We make two types of bells in the ceramic apse at Arcosanti: plaster mold bells and silt-casted bells. Both of these methods use the slip-casting technique, meaning we pour liquid clay into the molds to form the pieces, rather than throwing them on a wheel or hand building them. The silt-casting technique, which is the more unique of the two processes,  is demonstrated in this video:

In this video, we see the "600" model bells being cast, which include: 

These models are available for purchase on our website and in-store at both of our gallery locations
To experience silt-casting with your own hands, sign up for the Bell-Making Experience at Arcosanti where you will have the opportunity to cast and carve your own one-of-a-kind ceramic bell. This process involves using clay and dirt to create your bell, so come prepared to get your hands dirty! 
Photos by: Angela Piro, Ana Catalina, and Sagarika Bhati