Well, here I go.
It is kind of difficult to make an all-black eye look human.
Lighting variations change the effects pretty dramatically.
These are two of the first enamels officially for the AlterPieces project. Both are different takes on Solomon Wrax, a Chaos Space Marine from the Warhammer 40k universe. He is a scary, dangerous man.
Both pieces (and all of the enamels planned for the project) start with a slightly domed 40 x 30 mm 18 gauge copper oval. From there, unleaded enamel is sifted on and fired to form the base coat. To prevent air bubbles getting trapped in the glass and causing later problems, multiple extremely thin layers are built up until it is thick enough to suit the application.
Slowly emerging from the gloom.
For the full face piece, done with the grisaille technique, an opaque black was laid down first. I then proceeded to burn the ever-loving hell out of it (on purpose!) until the glass absorbed the copper and went from opaque black to transparent blue. Once the color was right, I painted on a thin layer of powdered translucent white and scratched it back to reveal the black. Upon firing, the white disappears almost completely. By painting on successive layers and firing them, laying down the white in smaller and smaller areas each time, you build up a gradation from the dark background to the white high spots. Great for dramatic shadows!
More traditional versions of grisaille, using an opaque black.
Pardon the dancing images, I'm still getting the hang of making gifs.
For the piece with the eye alone, I began with a clear base coat and then layered on scraps of 24 karat gold foil. It is slightly thicker than gold leaf, but nowhere near household tinfoil. The gold is held down by a few drops of liquid, dried thoroughly, and then fired on until the underlying glass gets soft enough to stick to it. Upon pulling it out of the kiln it looks discolored, but applying the next layer of clear enamel brings it back to shiny gold. Not liking the color of the base coat, I applied transparent blue enamels. Following that, a black pigment with no glass in it, treated much the same as the gold foil by heating the piece until the underlying glass sticks to it.
Just couldn't leave it alone.
I was planning on stopping here, but the layer of transparent enamel over the black pigment didn't quite work for me. Thus, I opted to go with more color and a more complete rendering of the eye while still letting the gold and blue of the base coat come through. The colored paints are a mix of overglaze, painting enamel, and watercolor enamel. The blue and gold isn't really the correct colors for the specific type of Space Marine (Wrax is a Night Lord, not a Thousand Son), but so it goes.