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Picture of Ceramic Wall Art
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
 
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Step 1: Roll a slab of clay

Picture of 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

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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

Picture of 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

Picture of 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

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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

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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

Picture of 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

Picture of 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

Picture of 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

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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

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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

Picture of 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
spoon566 months ago

I take a lot of different impressions with clay and found that laying a piece of tissue paper on the clay slab just before taking the impression prevents the clay sticking to the wood, concrete, whatever. Paper mostly peels right off afterwards.

How much did you spend (aside from the tools)?

fire18882 years ago
Most excellent! I can imagine there must have been quite a bit of trial and error for you in the process of learning how to get it right, my hat is off to you!!! Love all that texture and color!
blopez2 years ago
This is beautiful. You only show making one mold, but from the look of the variety in the finished product, it looks like you made several molds. How many different ones did you use?
johnwhitmarsh (author)  blopez2 years ago
I think I had maybe seven or eight molds. With all the color variations, you can get away with using the same casting and it won't be readily noticable when they're mixed together.
Ninzerbean2 years ago
When you write in step 3 "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." 1. Are you spraying the wet or dry clay with shellac?
2. Why Shellac? Are you trying to make the foamcore water tight? Can you use polyurethane or does it have to be shellac.
3. At this point is the clay still on the drywall that you trimmed to size and did you trim the clay to the size of the drywall or the drywall to the size of the clay?
4. So is the wet or dry clay on a piece of drywall inside the foam core box?
5. At what point do you spray on mold release - after the clay is dry, the shellac is dry?
6. Do you really only spray the mold release in the box or do you spray it on the clay that is or is not on a piece of drywall?
7. Your drywall looks like it is covered with tape or something. My drywall leaves a powdery plaster dust on everything it touches, if I trimmed the clay on the drywall it would get plaster dust in the clay which I am told will make the clay blow up in the kiln. It would be even worse if I trimmed the drywall while the clay was on top of it.
Sorry for the questions but I think there is a picture or two or a step missing and I am trying to follow it. Thank you.
johnwhitmarsh (author)  Ninzerbean2 years ago
Thanks for your questions. Here's some clarification:

1. Shellac is sprayed directly on the wet clay. The shellac will dry even though the clay underneath is still very wet (like magic).

2. I haven't tested other products, but shellac produces great results every time, and it dries extremely fast. Most materials have to be sealed prior to applying mold release, otherwise the RTV rubber will stick.

3. You can cut your tiles to match the size of your drywall, or vice-versa. In any case, you'll want to make the drywall a bit larger than the tiles to allow for airflow, and to make it easier on yourself when you work with floppy wet clay.

4. The entire box is sealed foamcore.

5. Mold release gets sprayed after the shellac is dry -- clay will still be very wet.

6. Mold release gets sprayed on every part that the RTV rubber will touch (clay and box). Under the clay is not necessary.

7. Yes, drywall edges get taped.
In question #4, I know the box is sealed foam core, but is the clay still sitting on the drywall while sitting inside the box? Thank you.
johnwhitmarsh (author)  Ninzerbean2 years ago
The clay is carefully lifted off the drywall and placed into the sealed box. I suppose you could construct the box walls directly on the drywall itself, but keep in mind that the drywall is actively wicking moisture from the clay, shrinking it as the hours go by. Makes the process more time-sensitive.
Potter John2 years ago
I agree with woodNfish, this is a very well done Instructable. Being both a potter and a lover of old worn surfaces that show a character all their own, this one is right in my aesthetic wheelhouse. I like the ideas you used to master from the subject with clay, make a rubber mold and then a plaster mold for durability in use. You still have the rubber mold to make another plaster mold as it starts to wear out or loses absorption. Good project, John. Putting the color on the plaster mold was a recent article in Ceramics Monthly, so you are also cutting edge.
johnwhitmarsh (author)  Potter John2 years ago
I appreciate the feedback. Backpainting the molds is a bit tricky, but the results are worth the effort.
1inspirit2 years ago
CREATIVE, INSPIRING AND AMAZINGLY ORIGINAL ! THANK YOU.
woodNfish2 years ago
This is a really good instructable John. Thank you. While I am not interested in making a tile mural you taught me a number of things; mold making with rubber, using shellac to seal the mold, how to make and use plaster casts for texturing clay, using a tile saw to cut fired clay (Duh!), and silkaflex instead of liquid nails. All useful stuff.
That's radical. That would be an awesome accent piece to replace the tiling/glass on my coffee table. Or maybe a backsplash to the bathroom? Or backyard garden tiles? THE POSSIBILITIES ARE ENDLESS!
ChrysN2 years ago
Wow, that looks gorgeous!