Raised-Line Tile Making: The Flores Tile Thomas Gelsanliter

Appears in the Sep/Oct 2016 issue of Pottery Making Illustrated.

Ever since I began drawing, I’ve gravitated toward line drawing. The directness of the single line has always fit me well. Reflecting back on it now, it’s not surprising that once I learned to make tile, I would be drawn to a technique that complemented my interests. I produce tiles using a centuries-old method of raised-line tile making called Cuenca. One of the tiles my wife, Sarah, and I make in our studio is called the Flores tile. It’s inspired by Mexican hand-painted tiles that have a wealth of motifs and iterations. I visited the town of Cuernavaca, Mexico, and was inspired to make tiles emblematic of the work I saw there.

Drawing the Design

I begin by drafting a design on paper. The Flores design is based on a freehand sketch (1). To make the drawing usable with the Cuenca technique, I adapt and stylize the sketch by enlarging it and redrafting it on tracing paper (2). Knowing that the black line in the drawing will become the raised line in the final tile, I omit any shading or color from the drawing because added detail obscures the lines once they’re transferred and carved into the plaster mold.

Rubber Mold Master

I prefer to create rubber master molds of my tile designs so I’m able to make multiple plaster molds and therefore larger production runs of the same design. I start the process by pouring a 66-inch plaster slab, squaring it off using a tile saw, then smoothing its surface first with drywall sandpaper then with increasingly finer grits of wet/dry sandpaper (200–600 grit) (3). I use molding plaster, although #1 Pottery Plaster works fine as well.

Next, I make a rubber negative of the blank tile and then a rubber positive tile. During the first rubber pour, I keep at least a -inch rubber border around the perimeter of the tile to maintain overall stability. I use Polytek 74–40 room-temperature vulcanizing rubber (RTV). With a rubber tile in hand, I can now make a plaster mold of it (4). I always wash the rubber tile with Dawn dishwashing liquid before pouring the molding plaster. The dishwashing liquid leaves a very thin layer of soap on the rubber tile, making the surface slicker. This helps reduce any chance of air bubbles being trapped on the skin of the rubber tile. Once the plaster hardens, I allow at least two hours before de-molding. Experience has taught me that demolding a rubber master too soon after the plaster sets can delaminate some of the plaster onto the surface of the rubber tile. This can “rough up” the surface of the cavity into which the design will be carved.

Note: While I use plaster and rubber molds to create my tile blank, it’s also possible to model a very smooth, blank tile out of clay and then pour a plaster mold of this. In either case, it’s important to let the plaster mold sit at least one hour after de-molding, allowing the surface to dry out some before transferring the drawing to carve. Attempting the transfer of an image too soon after de-molding can result in a splotchy, less crisp image.

Transfer the Drawing 

To transfer the drawing to a plaster mold of a square tile, the drawing needs to be sized to fit inside the mold and then photo copied. I like to make a few extra copies so I can color the drawing and begin to visualize how glaze will complement the design.

Place the design face down in the mold. Brush acetone over the paper to dissolve the ink and transfer the line drawing onto the plaster surface (5). I use a modified dental tool along with a plastic circular template to carve the plaster mold (see 6 inset). Note: Only carve the mold after the plaster has set, but before it has completely dried. A very dry mold may be brittle and therefore more difficult to carve. The first step in the carving process is to do a trace carving of the entire design (6). Do a quick pressing with a small ball of clay to see if the character of the design is consistent with the drawing. After the clay test, go back and deepen the lines, checking for consistent line weight along the way (7). Once complete, let the plaster dry fully.

Next, hand press a tile so you can bisque fire it and color testing can begin. I like to run a test piece to make sure the lines are consistent and tall enough so the glazes don’t run together. Later, I pour a final rubber master of the carved tile after seeing how the carving performs in a glaze kiln.

Hand Pressing

Hand pressing a Cuenca tile is a tricky process as it’s important to apply enough even pressure to the entire surface in the mold cavity so all the carved lines have consistent height. First, make a square pancake of clay about 3⁄8 inch thick. After placing the smoothest side of the pancake face down into the mold, begin in the center and press with both sets of fingertips, working your way to the top and bottom sides of the tile. Continue pressing to complete one side and then move on to the other (8). Finally, fill the mold with clay then scrape away any excess clay, leaving the surface flat and level with the walls of the mold.

To demold the tile, simply take a slug of wet clay and push it at the perimeter of the pressed tile toward the center (9). Once all the clay has released from the sides of the mold, use the slug again to help stick and peel the soft clay tile from the mold (10).

Drying Tile

The sooner you can get the tile to rest in a place that allows it to dry on all six sides the better. We dry our tile on wire racks. When tile has to sit overnight, we place it on HardieBacker cement board (before edging), slide the boards into tall, rolling metal carts, then tent the whole cart with plastic, thereby slowing the drying process down. This helps inhibit the tile from warping. It also keeps us from handling the work too much during the wet stage. Once the edges are cleaned up, the tile is left to dry fully then bisque fired flat.

Bulb Glazing

Before applying the first glaze, generously spray the bisque-fired tile with water and wait until it’s all absorbed. This is an important step as the water-saturated bisque allows for a smoother distribution of glaze as it’s being applied. Fill a bulb syringe with a metal tip attached to the end of it with glaze. Test your glaze thickness to make sure the glaze comes out of the tip at a controllable rate and doesn’t clog the tip, then squeeze the glaze to pool it into the confined areas delineated by the raised lines (11).

We use 2-ounce bulb syringes to apply glazes. They can be purchased from a pharmacy or ordered on the Internet. The metal tips are a separate piece that is attached by hand to the end of the bulb each time a new glaze is filled in the bulb. These tips, available from Axner Pottery Supply (www.axner.com), come in four sizes. The size of the tip corresponds to the number of rings inscribed around the bottom of the tip. A one-tip has one ring around the bottom and has the smallest diameter tip. A four-tip has four rings and has the largest opening, allowing more glaze to flow out more quickly when bulb glazing.

If you mistakenly apply a glaze to the top of a line or in the wrong area, use an X-Acto knife or a needle tool to scrape off the glaze. Then use a small dense sponge or a make-up sponge to remove all the glaze from the surface.

Once the entire surface has been bulb-glazed and it has fully dried, dip the edges in glaze and wipe away any excess drips with a dense sponge (12).

A Note About Waxing

I try to do as little waxing on my tile as is functionally possible. For the Flores tile and any other tile that doesn’t require an edge-glazed condition, we dip only the bottom quarter of each side of the tile. For us, this is a material and labor saving practice. We use a soy-wax blend. Like any material, this kind of wax has its own intrinsic properties.

We’ve had best results when the wax is applied to room-temperature ware and that the waxed pieces are glazed within a day or two of application. Handling the waxed edges can cause flaking of the wax after a few days.

Finishing Tile In The Kiln

Tiles larger than 66 inches are fired flat in both the bisque and glaze firings. All of our tiles are fired to cone 5–6 in electric kilns. We slow the glaze firing down during the last 60° of the cycle, hold at top temperature for 10 minutes, and fire down from the top temperature at 1° per minute for 25°. This allows for the glazes to mature and give us the glossy and satin look we want. If the raised lines of the tile have been carved evenly and are tall enough, color separation is confined and distinct. If not, this is an indication that the master mold needs fine tuning to deepen the lines. Once I’m happy with the final glaze, the rubber master tile is made and full-scale production can begin.

Thomas Gelsanliter and his wife, Sarah, own One Acre Ceramics, which they operate out of their studio in Milan, Michigan. Tom’s prior experience included work as a mold maker, production manager, and project manager for the Association of Collegiate Schools of Architecture. His designs are influenced by travel, industrial plate ware, quilting, Arts and Crafts, and folk-art iconography. Check out more at www.oneacreceramics.com.

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