​​Glazing the tesserae:    I spray on the glaze, rather than brushing or dipping, which led to very inconsistent results.   The spray nozzle attaches to a standard one pint jar; I have dozens of jars with a different color glaze in each.  The jars make it easy to change color.  The tesserae are sprayed in large groups, sitting on a lineoleum tile (this makes it easier to handle them.)   They get a total of three to five coats from different spray angles to a thickness of about 0.2 to 0.4 mm).  Glaze thickness can be tested in the overspray area.  Viscosity is critical; the glaze must have just enough water to go through the spray orifice easily.  This determination has been more a matter of experience; viscosity measurements have not helped much.  Between colors I wash off the sprayer with a garden hose, shooting some water through the orifice.

I use cone 5 and cone 10 clays; this results in tesserae which can last outdoors for decades.

Glazes:  I started out with premixed Spectrum products at cone 5 or cone 10.  The colors I chose are similar to what you find in a watercolor palette.  These glazes are opaque; they don't change color radically as they turn into glass.  it is possible to mix these colors to achieve intermediate shades.  By now I use a lot premixed glaze in powder form as well. 

Making clay tesserae (tiles)

The picture shows clay (Laguna B mix with grog) rolled out to a thickness of about 0.19 inch (5 mm), similar to the thickness of bathroom tile.  The cookie cutter elements are 3/4 inch copper pipe couplers which I have flattened slightly to be semi-square.  The clay sits on a batt, in this case a linoleum floor tile. ( I wouldn't want to handle the clay slab without a batt.)  As you can see, the idea is to make tesserae by the hundred, not just one at a time.

Other cookie cutters, in this case made from recycled metal strapping.  These make a variety of interesting shapes.  .


​I tried out my color palette by doing the same sparrow over and over.

​I began to experiment with black and white, with the idea of tesserae as pixels (as you would see in an over-magnified digital image),and with two colors of grout in the same mosaic.

Kiln:  an electric Skutt KM818.  It has five shelves with 5 cm spacers.  The total shelf area is 0.75 square meters, enough for several thousand small tiles. In making tesserae, I needed lots of shelf space. To load the kiln, I slide them off the linoleum tile onto the kiln shelf.   

​As the sheets of Hardibacker get larger, I use steel for reinforcement.  This perimeter of this framework is Lshaped steel, welded together. The horizontal braces are "hat channel', a stucco worker's product.  Hardibacker is attached using construction adhesive and pop rivets.   

​Substrates:   ​I generally use 1/4 inch thick Hardibacker as a substrate for flat 2D mosaics.  Tile adhesives adhere well to this material.   Hardibacker is not structural and needs reinforcement.  I glue smaller pieces of Hardibacker.

 The picture at right shows a framework of 1x2 pine, attached to the Hardibacker with construction adhesive and rust-resistance screws.  The wood is lap-jointed; lighter than a solid sheet of plywood. This substrate already has a picture frame and French hanger attached.

On the left is a plaster of Paris mold.  It replicates 18 mm metal beads, giving the clay a lot of detail.  By now I have dozens of plaster molds. 

Below are some finished bead replicas. 

​Mosaics   ​Early on, I created mosaics by taking whole tesserae from my 'library" of 3 sizes and 30 colors and gluing them down one tile at a time.  I use a standard thinset, which comes in powder form, and mix up small batches as I need them.  This technique required very little cutting and fitting.  Composition/assembly were very fast.  The large tesserae forced me to create large mosaics in order to have any detail.  I started creating more shapes, like the linear tiles in this pomegranate.