Lessons in Building a Grandisimo Mosaic Tile Mural

A year ago I started working on a grand project. To create a 600 square foot mural on a garden wall at our casita in Oaxaca, Mexico (see my previous post for “before photos”). So it has been 1 yr since I began this epic journey and I thought that I might share some of the things that I have learned thus far…. not to mention the fact that I am excited to share my progress!

True to my nature, I started this project having no idea what I was doing. I had a little mosaic experience under my belt having taken a mosaic class with local artist & friend RHODA KAHLER.  Up to this point my mosaic experience was limited to garden decorations that I have made for my home here in Pennsylvania. These were quickly followed by the Ronald McDonald House 25th anniversary mosaic mural project that I organized with a group of volunteers and graphic designer KATHY O’CONNELL . Through this project I met another local mosaic artist JESSICA GORLIN LIDDELL   and took a class with her. Making outdoor mosaic projects here in PA presents many challenges due to the harsh winter weather. Making a project that will survive many years of freeze/thaw cycles is a daunting task.

I once lived just 2 blocks away from Philly’s Magic garden that was created by artist ISAIAH ZAGAR .  His murals were beginning to pop-up everywhere along South Street.  I met Isaiah once, but it was not at the Magic Garden nor at the Eye’s Gallery that is owned by his wife. I  had to go to San Martin, Oaxaca to meet the guy!  We met at the work shop of ZENY FUENTES, a wood-carver & creator of “alebrijes”. It’s kinda strange that I would meet this famous mosaic artist in a tiny Mexican Puebla 5 years before I knew I would have a house in Oaxaca, and before I had any thought in my head of making a mosaic mural there. It’s not just strange, it’s a little spooky.

So this blog started out to be instructional… to share what I learned, and I apologize for taking so long to get to the point. I hope that you will find this information useful and that you will be inspired to give mosaic-ing a whirl.  Perhaps what I have learned will help you.

Here in PA we have to deal with winter. Not so in Mexico! No worries about ice popping tiles off the wall, no need to avoid using earthenware tiles, no needing expensive acrylic/latex mortar & grout additives, nope none of it! Being free of these worries allowed me to work in the manner in which I am happiest “make it up as you go along”, dive-in head first without really having any idea of what you are doing, start with an impossibly huge project before knowing how to do a small one!   I’m going to stick to my experience with winter-proof mosaics for this discussion.

WHAT I HAVE LEARNED through my experience, talking with experts, & reading manufacturer’s specifications & instructions about making a mosaic tile mural in a northern climate:

Tips for a successful (long-lasting) exterior mosaic project in locations with below-freezing temperatures in winter:

1. Ideally you should use tiles, mortar & grout designed for EXTERIOR use.  All tile products are rated for outdoor use,  frost resistantance, & if it is impervious to water.  A “yes” rating in all 3 categories is what you want

2.  You cannot use mastic or glue (not even the famed weld bond) to adhere your tiles.  You must use thin set mortar &  MAKE SURE it is for EXTERIOR use.

3.  You  cannot mosaic onto wood!  Wood expands & contracts in response to changes in temperature & will pop off your mosaic pieces in doing so.  Wood also absorbs water… a no-no for success in winter climbs!

4. You cannot mosaic onto surfaces coated with the new-fangled “stucco” known as DRYVIT.  The weight of the mosaic will pull the dryvit right off the wall!

5.  You can mosaic onto cement, brick, cinder block, hypertufa,  cement board, and stone.  Porous, unsealed surfaces that allow a “tight grab” for the mortar to cling to

6.  NOTES ON USING EARTHEN WARE TILE:   Most wall tile that you will find is made of soft-fired earthen ware.  Yes it is beautiful, yes there are amazing colors!  But if you want  the closest thing to a guarantee that you project won’t fail DON’T USE THEM or your broken earthen ware dishes.  Yes, go-on & argue with me.  I know millions of people use them, Isaiah uses them, but they won’t last, they may not survive the first winter.  Earthenware tiles are porous, they absorb water, water freezes, when it freezes it expands, when it expands your tiles break…  and you are left with ugliness.  Mosaics take a lot of time, effort & money,  it’s important for the thing to LAST.  If you MUST use earthenware tile I suggest the following:  Use smallish pieces and make wide grout lines.  Wide grout lines will make the tile more durable.  The gout lines on Isaiah’s murals are VERY WIDE, sometimes an inch or more.  But his murals are enormous & the scale of his projects make these grout lines appropriate.  If you want to use these tiles make something small & move it under cover in the winter.

7.  CHOOSING WINTER-FRIENDLY mosaic materials:

1.  If you are BUYING commercially made tile for your project, porcelain tile is you best choice. It will not absorb water that will freeze & break the tile.   Most floor tile is porcelain …. check the manufacturer’s specs to be sure.  Solid color porcelain comes in an amazing range of colors but needs to be SEALED before using or it will be uglied-up by your grout… again READ the specs!

2. If you are MAKING YOUR OWN TILE: I have had great success using architectural stoneware clay fired to cone 6.   This clay is heavily grogged & sanded to prevent excessive shrinkage during firing.  It also has a final absorption rate of <1%… check with each manufacturer’s specs or consult with your supplier before choosing your clay. I use a slab roller.  I start out with the roller set at 5/8″ & roll the clay through 3 times decreasing the thickness by 1/8″ , FLIPPING & TURNING the slab 90 degrees with each pass.  The final pass is at a setting on 3/8″, which after subtracting the canvas leaves me with a 1/4″ slab.

To make FLAT TILES I allow the clay to dry between dry wall boards to soft leather-hard before cutting to minimize stretching.  The clay is still soft enough at this stage for any stamping, or embossing that you may choose.  Once tiles are cut, I try NOT to move them again until they have been allowed to dry for several days between boards.  I slow-fire my tiles.

To make SCULPTURAL (3D) Tile:  When we prepared sculptural tile for the Ronald McDonald House project, we kept our tiles at a maximum size of 11″ square and 1″ thick at the highest peaks.  All of our tile had troughs of clay removed from the back to allow a place for mortar, and to reduce the weight/thickness of the tile.  During installation it is important to make sure that the voids on the reverse side of the tile are completely filled with mortar!  Our tiles were built up by adding clay to a prepared slab.  To make sure that we did not have any trapped air, we pierced each tile hundreds of times with a needle tool and then repaired the face of the tile to remove/re-seal the holes.  The holes were NOT sealed back up on the reverse side of the tile to allow any trapped air to escape.

3. GLASS TILE:  not all glass tile is created equal!  Check the tile specifications to be sure that is for outdoor use, frost resistant, and impervious to water.  GLASS BLOBS  found in dollar stores & floral departments are not a good choice. They break & pop-off with frequency

4. GLASS MIRROR: I like to use pieces of mirror in my mosaics, but  it may not last.  Although the mirror has not popped off my mosaics, some of is has lost its reflective property because the silvering has turned grey.  I can’t say for certain, but mirror that I bought from a glass supplier and that was 1/4″ thick, made for “architectural use”, and was more expensive, seems to be holding up longer, but who knows for how long.  I would not use cheap mirror from home stores, mirror that is thinner than 1/4″ or anything that you bought cheap in a frame.

8. CHOOSING MORTAR & GROUT: Consult manufacturer’s specifications & select products specifically designed for exterior applications.  Always use sanded grout. Spend the extra money to buy their best products and the recommended acrylic/latex additives. These products allow for a wee bit of flexibility during freeze-thaw cycles thus helping to minimize tile loss   You will never regret using the best!

9. Cleaning tile after grouting:  The thing that I hate most about doing mosaics is sponging after grouting.  You have to sponge multiple times & then you still end up polishing each individual piece with a dry rag to remove the haze.   I found that if I waited until the grout was at just the right stage of “curing” I could rub off the excess with my gloved hand which served to both clean/polish my tiles and firmly compress the still soft grout into nice tight grout lines! You need HEAVY rubber gloves for this.   If your timing is just right, there is NO HAZE!  If you do see hazing, wait a couple more minutes & try again.  It is a good idea to wet the entire mosaic down with water the following day… I am told that doing so makes your grout stronger.