Process
Traditional cameo glass is carved. This work is not. The image forms in the kiln, and it is planned before any glass is cut.
From photograph to glass
Each piece begins as a photograph, often one the artist took on film years before. Its tones are translated into a digital relief, with light areas and dark areas becoming different depths. That relief is inverted and mirrored to make a 3D-printed model, and the model becomes a mold.
The mold is filled with glass and fired once, a pâte de verre method. Where the glass is thin, light passes and the image reads pale; where it is thick, it reads dark. The photograph reappears in the glass itself, the way a lithophane holds an image in porcelain.
Most of the pieces shown here were made from models printed on an FDM printer (a LulzBot TAZ 5). FDM prints in horizontal layers, and the banding it leaves carries through the refractory mold into the glass; look closely and it is there in the surface. In 2019 the artist moved to resin printing, which removes the banding and gives a far cleaner mold positive, and a marked improvement in the glass.
Lithovitrum
Lithovitrum is a method the artist developed and named. A patterned piece is made first, by the same pâte de verre method. A layer of transparent coloured glass is then laid over it and fired a second time; the coloured layer reveals the photographic image. A cameo piece is fired once; a Lithovitrum piece is fired twice.
Examples include Chimayo, Solitude, Death by a Thousand Cuts and Dale Chihuly.
Light
Because the image lives in the thickness of the glass, lighting changes it. The same piece can read cool or warm, sharp or soft, depending on where the light comes from.
Enclosures
Some pieces live in enclosures the artist builds by hand. The glass itself is used as a mold for hand-cast archival paper made from cotton linters, so the paper fits the piece exactly and holds it steady.
The glass library
“Before I select or layer a single piece of glass, I already know how it will behave, because I measured it, and built the tools to make that knowledge usable.”
Choosing glass for a cameo piece means knowing how each colour reads at every thickness. The artist built a library of Bullseye glasses: 167 colours with 333 measurements of reflected and transmitted colour, taken from scans of each sample. It is a practical design tool rather than laboratory spectrophotometry, and it lets him predict how a colour will darken with depth, or how one glass will read layered over another.
Tools & software
The library and the mold-making tools grew out of Python scripts and command-line programs. The artist wrapped them in a single application, the Glass Library & Model and Mold Toolkit, so that other glass artists can use them without the command line. It generates cameo and vessel mold models, plans mold materials, predicts layered and frit colour, and keeps kiln firing notes.
The code is open on GitHub. The mold generator needs a lot of memory, so the toolkit runs best on a local computer with 32 GB or more.
Experiments
Alongside the cameo work are tests and side paths: cast glass from 3D-printed molds, machine-drawn sgraffito, and early pieces made from particle-chamber photographs.