I was commissioned to create a large house number plaque for a residence in a dark wooded area. The numbers needed to be reflective for easy detection at night as well as high contrast for the daytime in this wooded area. The plaque was to provide an attractive marker for the house but also make the location easy to detect for visitors or an emergency. Their choice was to use large ceramic reflective numbers on three sides of a natural red cedar post to match the forest environment.
3D Printing Stamps
To create the large tiles with numbers of 6×4 inches for a 4×4-inch post, I decided individual tiles were the most reliable as well as the most attractive. I chose to use 3D printing to create the custom number stamps. There are numerous online 3D printing companies if you do not have access to a printer yourself.
Next, I used Microsoft PowerPoint to create the images with a chosen font. The easiest solution is to print the number white on a black background since most 3D printing solutions have white as “high” (i.e. indents in clay) and dark as “low” (not indenting or not as deep in clay). Gray scale for graded indentation in the clay can also be used, but I didn’t use this feature in this project. Note: Numbers need to be printed as a mirror image to have the stamp create a readable number when pressed into the clay slabs.
The mirror image (1) is created with the Flip Horizontal feature in any image processing program. My favorite free image processing software is ImageJ (https://imagej.nih.gov/ij), which is extremely powerful for most photo-manipulation chores. I scaled the numbers to the appropriate size, added a uniformly sized rectangle around each number, and printed them. The enclosing rectangle serves as the tile outline, reducing the steps in processing as you will see later.
After checking the printouts for scale and placement, I send the digital image files to Sculpteo.com. Many other online companies are available. I specified the material and style (image with depth in white plastic). I’ve found that the white plastic works very well when stamping clay. The stamps were made with ¼-inch-high numbers generated to assure a deep impression (1). In my case, I had the stamps within a week of uploading the images. The stamps are very durable and hold up to repeated use even on near leather-hard clay after trimming.
Creating the Ceramic Tile Numbers
Roll out a ³⁄8-inch-thick stoneware slab. Smooth the slab with a metal rib, spray the stamp with a silicon lubricant (I use Dupont Teflon Silicone Lubricant or WD-40) to aid in separation, then push the number stamp into the clay using the gap between the frame of the stamp and clay to gauge the depth (2).
Before removing the stamp, use the frame as a guide to trim the tile. This ensures that the relationship of the number and the outline of the tile are identical for each pressing. Any spreading with the impression is compensated for by making the pressing on an intact slab and not a pre-cut tile. Remove the stamp (3). Some clean up work may be necessary to eliminate minor distortions. Dry the tiles slowly to minimize warping.
Reflective Surface and Glazing
The finished number tiles have a dark blue outline around a reflective white number. The reflective numbers were created by applying a commercially available reflective acrylic paint to the fired tile as outlined on page 7.
Bisque fire the tiles to cone 06 and then glaze the number’s outline with a dark cobalt blue glaze for contrast (cone 6 Cobalt Blue Glaze: nepheline syenite 46.2, Gerstley borate 28, silica 20.4, EPK kaolin 5.4, bentonite 1, and 0.5 cobalt oxide). After the glaze firing, I used a commercial grade white acrylic paint used to mark roads (Cole Safety Products, Acrylic White Paint.) It’s very tough and works well in outdoor environments. This process works best when first applying the paint, then adding the beads (Cole Safety Products, Reflective High Index Glass Beads) to the wet paint and letting them dry into the surface of the paint. I infuse the paint into the numbers with a syringe that’s thin enough to get through the narrowest part of the imprint (4). This approach yields a thick, even layer of wet paint. The reflective glass beads are sprinkled liberally, nearly filling the imprint, before the paint has a chance to dry (5). After drying and carefully removing the excess glass beads, the highly reflective tiles are ready for mounting.
6,7 Tiles mounted on a post, shown in daylight and at night. The reflective paint provides a very visible, high-contrast sign.
The tiles are attached to the cedar post with a combination of multimedia glues (Gorilla Glue and Gorilla Construction Glue) applied to the back of the tiles and on the wood. The signage is clearly visible during the day and highly reflective at night (6, 7) making an attractive and useful house number plaque.
Robert S. Balaban, PhD, has operated the Stone and Ash Pottery in Bethesda, Maryland, for the last 20 years and has made several contributions to Pottery Making Illustrated.