I’ve always loved the texturing of old utility poles. They’re a ubiquitous sight in the city and no two look alike. Some are cracked and weathered from the sun and rain; some are charred; some have creosote and chemicals leeching out. I wanted to recreate each variation in a ceramic tile wall mosaic that could be displayed indoors.

Materials List:

rolling pin
canvas
wooden sticks
basic clay tools (slab wire, needle tool, sponge)
foamboard
spray shellac
hot glue
straightedge
utility knife
paint brush
spray mold release
RTV rubber
plaster
5/8in drywall
wet saw
clay
underglazes
caulking gun
Sikaflex
1/2in plywood
acrylic paint

Step 1: Roll a Slab of Clay

Using a rolling pin, roll a chunk of wet clay into a slab. I’m using a basic ceramic clay (EM-210) because it’s easy to work with and cheap. Wood sticks (1/2in thick) placed on either side will ensure an even thickness. Heavy canvas placed underneath will prevent the clay from sticking to the table.

Step 2: Create an Impression

Mash the slab into the part of the utility pole you want. Peel away a corner to remove. Place slab onto a piece of drywall (texture side up) and trim to exact dimensions.

Step 3: Make a Rubber Mold

Spray shellac onto a sheet of foamboard and let dry. Construct a tray using a straightedge, utility knife, and hot glue; make the inside dimensions 1/2in-1in larger than the clay tile. Place the slab carefully into the tray. Spray the slab with shellac and let dry. Spray mold release agent into all surfaces of the entire tray, and place on a level table. Mix RTV rubber and pour slowly into pan, starting in the corner. Fill to 1/4in+ above the tile.

Step 4: Pour in Plaster

After rubber has vulcanized, remove it from the tray and flip over. Remove any bits of trapped clay with a toothbrush. Spray with mold release and work into the crevices with a paintbrush. Pour plaster slowly into the mold, starting in the corner. When plaster hardens, remove it from the rubber mold and allow to dry fully – this could take several days. You’re now left with a negative impression of the original pole. If the plaster were applied directly to the pole, it wouldn’t be able to be removed.

Step 5: Press Clay Into Plaster

Roll a slab of clay as described in step one and press it firmly into the dry plaster mold. Trim excess clay from the edges with a needle tool.

Step 6: Peel Back

Peel back the slab to reveal the texturing. The drier the plaster, the easier the clay will peel away. After repeated castings, the plaster will absorb moisture and start sticking. To dry the plaster out, it can be placed in an oven turned on low, or out in the sun if the weather’s warm.

Step 7: Coloring the Clay

To achieve multicolored castings, brush underglaze (liquid clay) directly onto the plaster mold. When the clay makes contact, it will bind together, taking the underglaze with it upon removal.

There are a few critical steps to follow:
1) apply 3-4 thick coats of underglaze and allow to dry between coats; drying means going from shiny to dull, but the underglaze will still be ‘wet’.
2) When the last coat has dried, lightly sponge the surface so that the high parts are completely clean and free of underglaze. This will allow the color of the clay itself to show through.
3) Spray the surface with a heavy dose of water immediately before pressing the clay into the plaster. This will make the clay stick. Wait for 30-60 minutes to allow the underglaze to bond to the clay, and peel back the slab. With any luck, most of the underglaze will stick to the clay, but it’s normal to have a little left behind. That’s okay because peeling works aesthetically with the haggard utility poles you’re trying to reproduce. Note: underglaze color should be lighter than the clay color.

Step 8: Drying the Clay

Sandwich the slabs between pieces of 5/8in drywall. The drywall will absorb the moisture and prevent the tiles from warping. Drying can be accelerated by placing them into an oven set to 150 degrees or under.

Step 9: Kiln Firing

When the pieces are bone dry, place them into the kiln and fire to the desired cone temperature. With the exception of the black charred tile, which is cone 5 Cassius Basaltic, most of the colors can be achieved with firings between 04 and 1 using Black Mountain clay and Cassius Basaltic.

Step 10: Cut Tiles to Size

Cut the finished pieces to exact dimensions on a wet saw. Although time consuming, it’s the only to way to make every piece fit together in a mosaic.

Step 11: Glue to Backerboard

Glue the dry tiles to 1/2in plywood. I like to prime the plywood with black acrylic paint so any gaps in between tiles will blend into the shadows. Sikaflex is a super-permanent adhesive that remains slightly flexible over time. Black is a good color because it will blend with the shadows if any glue oozes out along the sides. Note: priming with oil based paint can cause poor adhesion.

Step 12: The Finished Piece

The finished mosaic - 80in (h) x 56in (w). It was on two panels because of the weight. I installed it directly to the wall with screws. I left several spaces open without any tiles so I could apply the screws first, then reattach the tiles with museum wax. This will allow me to remove the tiles when I want to move the whole mosaic.

Overview:
The process is a bit involved, but if you take the time with each step, it’s pretty straightforward and you’ll have an awesome finished product. Most of the materials can be purchased at the hardware store and craft supply store. If you don’t own a kiln, you can find a place that will fire them for you (most ceramics shops do it.) For the wet saw, you can find a place that rents them, or go to a tile shop that will cut them for you in back. Here’s a list of resources in San Francisco:

Materials:
Ceramics & Crafts, 490 5th St. @ Bryant
Douglass & Sturgess, 730 Bryant @ 5th St.
Discount Builders Supply, 1695 Mission St.

Kiln firing:
Ceramics & Crafts, 490 5th St. @ Bryant

Wet saw rental:
Action Rentals, 1530 Folsom St. @ 11th St.

Wet saw cutting:
Ceramic Tile Design, 189 13th St. @ S. Van Ness