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How to Mosaic on Wedi Board

Silva has a technical background and is self-taught in the art of mixed media and mosaic. Her works are scattered all over the world.

Dave Mason in front of South Austin Music outdoor sign on Wedi board

Dave Mason in front of South Austin Music outdoor sign on Wedi board

Wall hanging installed in wooden picture frame

Wall hanging installed in wooden picture frame

One, Wedi cut to fit and siliconed into the back of a 16x20 artist canvas

One, Wedi cut to fit and siliconed into the back of a 16x20 artist canvas

Two, Wedi covered with a skim coat of white thinset

Two, Wedi covered with a skim coat of white thinset

The back of the finished piece, ready for hanging

The back of the finished piece, ready for hanging

Guitar shape, cut from Wedi, stained glass and pique assiette mosaic

Guitar shape, cut from Wedi, stained glass and pique assiette mosaic

My goal for these projects was to create a mosaic panel that was light weight so I chose Wedi board instead of plywood or other substrate.

Why? Because Wedi Board (pronounced "weedy") is an ideal substrate for mosaic artists. It is made of styrofoam encased in mesh and cement. Wedi is sturdy, light weight, and easily cut with a utility knife. Wedi weighs about one-fourth as much as cement board, and is one-half the weight of MDF or birch plywood.

It is rigid, waterproof, and weatherproof. It does not warp, does not require sealing, and can be used on floors, walls, and as art panels. It is made of a middle core of blue styrofoam with a reinforced polymer modified concrete coating on both sides. You can use Weldbond, silicone, thinset, Mac glue, etc. as adhesives.

I purchased Wedi board from Maryland Mosaics and later learned that there is a local source (Dal-Tile, Austin). They are wholesale but a phone call revealed that they make an exception for mosaic artists! Isn't that cool? Then I found out that my local stained glass shop, Blue Moon Glass, also carries Wedi. I purchased the Wedi for the outdoor sign from Dal-Tile and the black and white stained glass from Blue Moon.

The problem I had to deal with was the hanging system. I did not want to use the specialized hanging system that is sold for Wedi. I had a brainstorm whereby I developed a method that I've not heard of before, so let me pass this on to you.

I bought a 16"x20" artist's canvas that is called "gallery wrapped" or "staple-free edge." Some of these are stapled on the back. That's not the one you want. The one I used has a wood stretcher inside a wood stretcher, and the canvas is neatly tucked out of sight between the two rectangles of wood and you can't see the staples.

So, to begin, flip the canvas over and carefully measure the cavity. Cut the Wedi board exactly to fit. Pop the Wedi into the cavity and using clear GE Silicone 2, run a bead of silicone around the Wedi to seal it to the canvas stretcher.

My next step was to mix up a small amount of white thinset, also known as mortar, and apply a thin coat over the Wedi. This may not be necessary for you; I chose to do this because some of the stained glass I planned to use was transparent or translucent, and I did not want the ugly grey cross-hatched surface of the Wedi to show through.

Next I created the mosaic, using MAC glue to apply a variety of materials to the Wedi (the back side of the canvas). I used drapery stained glass, polished amethyst stones, costume jewelry, dichroic glass, sea shells, beach glass from Hawaii, flat glass marbles, Swarovski crystals, glass beads, and broken plates, (including the footers, thank you, Candace Clough), and terra cotta.

Note the squid passing over the sea floor. It began life as a silver earring but lost its mate and was thrown in a thrift shop box. Retrieved by me, it lay about in my stash of odds and ends for about ten years. Each time I ran across it, I thought, Hmmm, that looks like a squid. The tentacles are strings of tiny glass beads, threaded through a hole in the earring and tied off.

The ceramic pieces (orange, gold, green, and turquoise) were hand-made house numbers (a one, a zero, and an eight) that someone gave to a thrift shop. I bought them because they are beautiful but I changed their purpose and broke them into several pieces for this mosaic. Note the tiny little glass bottle and the little gold crown. Both seemed like treasure that might fall to the ocean floor.

This art panel is made up of many levels of mosaic tesserae. I carefully smooth the edges of each piece because when you grout mosaic art of uneven levels, you cannot always cover the sharp edges with grout. I use a simple hand-held tool called a Kitchen Sharpener (a wood-handled carborundum stone) that I buy at Breed and Company Hardware Store in Westlake Hills, Austin.

I grouted with charcoal grout, waited 24 hours, and sealed. I wanted the tentacles of the squid to dangle freely, so before grouting, I carefully wrapped them in a small piece of paper and taped it closed. I grouted all around the squid taking care not to get grout on the tentacles. Lastly, using Ceramcoat acrylic paint, I randomly dabbed various metallic colors here and there, mostly 14K gold.

Laying the piece face down, I installed little eyes and picture hanging wire on the back (what started out as the front of the canvas). I am quite happy with how neat and finished the back of the panel looks. A piece like this doesn't need to be framed. I just painted the wood stretchers and the edges of the canvas with black acrylic paint. However, I happened to have a nice wooden frame on hand, so I discarded the print and the glass and installed that frame onto the mosaic panel, again using GE silicone II to hold it all together.

I had a lot of fun with this free-style project.

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For the hanging system for the South Austin Music sign, I bolted the Wedi to the existing sign, using bolts with washers. I used about 25 bolts to make sure it stayed secure.

Here's a super video illustrating how to install a hanging system using tee nuts:

Here are a few tips and observations when using costume jewelry in mosaic work. Use a small wire-cutting tool to nip off the pins and backings. Be careful because they fly through the air with great speed, so plan on a way to contain them before nipping and protect your eyes. Next, examine the back of the piece and see if it is flat or hollow. I like to fill in hollows so the piece has a flat base. To do this, I nip pieces of popsicle sticks and glue them to the back, thus creating a flat piece of tesserae. You can nip dichroic glass just as you can ordinary stained glass (using wheeled nippers such as Lepponit).

This article discusses using costume jewelry in mosaic art: I also talk a bit about gathering up the tesserae needed for a project. A project like this one, with a theme of the ocean floor, opens up so many possibilities, because anything goes, and junk jewelry that has no other use whatsoever will add so much to the overall mosaic.

I talk about grouting in my hub When you grout a piece such as this, with the different levels, you will need to do some patting and smoothing of the grout as well as just squooshing it on and wiping it off.

Go to my blog to see other mosaic projects. Keep going to "older posts" and you will see the details of the mosaic stair risers I did (my largest project to date). I am in the process of creating a 24" x 48" piece based on outer space and the progress can be seen on my blog:

I also wrote a hubpage article about the stairs here:

Here's a large outdoor sign I made using Wedi board:

This is a small piece of a much larger mosaic featuring outer space, stained glass, costume jewelry, pearls, beads, and dichroic glass on mesh, to be applied to Wedi.

This is a small piece of a much larger mosaic featuring outer space, stained glass, costume jewelry, pearls, beads, and dichroic glass on mesh, to be applied to Wedi.


Rina1984v on January 13, 2019:

Brilliant Art Work, good for the interior

katie on September 07, 2016:

brilliant ideas!! Thank you so much! I have a question: I want to make a mosaic sign for outdoors, hanging from two wooden posts. Any suggestions how to attach the wediboard to the wood?

Cat on August 03, 2016:

Can you use wediboard for larger mosaics? And can you hang them without any crumble? Have you tried this?

Janice Strawder on July 19, 2016:

Hi Silva I am creating an approx 4' x 4' mosaic for outdoors. The last one I made was on marine board with hardibacker attached. I've never used Wedi board. I'm wondering if I can use the Wedi alone to install to the face of a concrete wall, (inside an old window well that has been filled in), and if Wedi is appropriate, can I use it alone without the plywood for rigidity? I want to create the mosaic indoors on the Wedi and transport to the site and then grout. Any advice would be greatly appreciated. This is a children's art camp project.

Silva Hayes (author) from Spicewood, Texas on May 09, 2016:

Yes, you should cover and reinforce the edges with tape first. Then go over that with thinset. You can smooth the thinset with a wet paint brush while it is still wet. After it dries, you can sand it. Then you can paint it.

ronna on May 09, 2016:

Should I do anything to the edges of the Wedi Board before beginning my mosaic? My edges, especially the corners, are a little crumbly. Should I be wrapping the edges with tape? I may or may not frame the finished piece but in either case I don't want the edges to crumble. Thanks!

I will be using glass, copper, and ceramic pieces in my mosaic and will probably use Weldbond to adhere them unless someone has a better idea.

Silva Hayes (author) from Spicewood, Texas on November 14, 2015:

Hi, Rhonda, yes, it is much thinner, like a medium wash.

Rhonda on November 14, 2015:

When you do the skim/scratch coat on the Wedi board, what ratio of water to thinset do you use? Is it thinner than the thinset you use for adhering the mosaic pieces?

Silva Hayes (author) from Spicewood, Texas on April 15, 2012:

What I have done is sink the staple into the wood slightly by placing a large screwdriver over it and carefully tapping with a hammer. Then paint right over it.

kravery on March 24, 2012:

What does one do with the staples that are on the corners of the wood frame? You said you painted that side them with black paint. Since you then put it in another frame I guess this part didn't show? What would you suggest if I don't have another frame in which to put it.?

Silva Hayes (author) from Spicewood, Texas on March 24, 2012:

Hi, kravery. Thanks for visiting. You will love this method; it makes a nicely finished, light-weight mosaic. Please come back and let me know how it worked for you.

kravery on March 23, 2012:

Love this. I too make mosaics and just discovered Wedi board but then didn't like the fact that the hanking system stuck up and can't figure how to mosaic over it. I am going to try your method.

Silva Hayes (author) from Spicewood, Texas on March 11, 2011:

Thank you, Edward.

Edward Dickinson from Dallas on March 11, 2011:

That piece is truly unique. Thank you for sharing your idea.

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