A few years ago, Karen J created a mosaic bench in her backyard using mining debris (large stones), cement, and chicken wire to form the base, which is similar the methods we recommend in our instructions for creating bases for outdoor mosaic sculptures. Karen modeled her bench after those made by the great mosaic architect Gaudi in Park Guell in sunny Barcelona, and she used brightly colored ceramic tile just as Gaudi had used. The problem is that Karen’s backyard is in Colorado, and so her mosaic experienced many long and hard freezes that a mosaic in Barcelona would never see.Mosaic Bench after Antoni Gaudi shows the ravages of freeze damage. Colorado winters are quite severe, but any temperature below freezing can crack and flake ceramic tile. Ceramic Tile Is Vulnerable To Freeze Damage
Glass mosaic tile is non-porous, and so water cannot seep in and freeze and crack it, and so glass is preferred for outdoor use, as is porcelain tile for the same reason. On the other hand, ceramic tile tile is very porous and soft, and so water can penetrate it (through tiny cracks in the glazing). Once this water freezes and expands, it cracks the ceramic tile and often causes the face of the tile to flake off.Mosaic Bench Detail showing freeze damage. Note that the empty sockets in the blue tile are NOT where tile has popped off. Instead, it is where the faces of the tiles have flaked off due to water freezing and expanding in tiny cracks and pores.
In the photo above, you can see how some colors were more resistant to freeze damage than others. This difference was not due to the color but to the variety of the tile: some brands of ceramic are harder and less porous than others. Also, some brands have thicker glazes, and that can also affect how permeable the tile is to water.Preventing Freeze Damage
You can minimize freeze damage by sealing your finished mosaic with multiple applications of a tile and grout sealer from your local building material store. Avoid ordering sealers online during winter months because water-based silicone sealers ruin if they freeze during shipment. You should also clean and reseal the mosaic each fall. Small mosaics such as mosaic stepping stones can be brought inside for the winter.Mosaic Bench Second Detail showing freeze damage. Imagine how bright the orange and yellow sun was before Freeze Meister blasted it and flaked off the color!
This method for altering a mosaic can be used before grouting, or grout can first be removed by scraping it out with a grout removal tool or screwdriver.Why Remove Tiles?
Even experienced artists modify their designs as they work on them, and beginners can’t help but use a trial and error approach. After all. it’s hard to plan exactly what you will do when you are just learning a new medium.
With drawing and painting, revision is easy, but what about mosaic? How do you remove and replace tiles after the glue is dry?Prancing Horse Mosaic Before Versus After shows the changes made by prying up and replacing tiles. The purpose of the change was to make the head more horse shaped. I think the mosaic could be further improved by making the mane and tail from the same umber tile used in the hooves and outlines. How To Remove Tiles SELECTIVELY From A Mosaic
The following method assumes the tile is attached to a plywood backer using a white PVA glue such as Weldbond. You could use the same techniques on an outdoor mosaic made with thinset mortar, but it would be very difficult if the mortar has cured for more than a few days. Mostly this method is used while you are working and see obvious mistakes, and the glue or mortar is not very hard.Soften The Glue If Needed
OPTIONAL: If needed, apply a few drops of water around the tiles in question to soften the glue. If the surrounding tiles get wet and unexpectedly come up or look like they might, you can pull them up and reglue them too.
Cotton swabs are useful for applying drops of water to precise locations. Dry cotton swabs are useful for soaking up excess water and containing the spread.Use A Metal Tool To Pry
VERY IMPORTANT: Use a ruler as a fulcrum to lean the metal tool on when you pry. If you lean the tool on the surrounding tile, you can split or crack the tile VERY EASILY without applying much pressure at all.Prying Up Mosaic Tile can very easily crack surrounding tile if you lean your tool on surrounding tile as a fulcrum. Instead, hold a ruler firmly in place and lean your prying tool on that. Scrape Off Broken Pieces
If the tile breaks into pieces, and some pieces are still glued down, you can scrape that off, but take care because the tool can slip, and then you can jam your hand into the razor sharp pieces before you are aware what is happening. Wear leather work gloves to avoid skinning your knuckles or cutting your fingertips open on broken tile.Repairing Holes In Backers
If you gouge a hole in the backer while scraping or prying, it can be repaired with Weldbond glue or glue mixed with sawdust if the hole is deep. If a layer of plywood gets snagged and sticks up like a flap of loose skin, squirt glue under it and apply a heavy weight on that precise location to hold it down until the glue is dry.Safety
Wear safety glasses with side shields RELIGIOUSLY when doing this work. Prying tile with a metal tool can shoot tiny splinters right at your face. Wear leather work gloves when scraping in case your tool slips.Mosaic Art In Progress. Sometimes you don’t see your art objectively until you start working on another mosaic. Thus, it is better to wait instead of grouting a mosaic right away.
Terracotta flower pots are highly susceptible to freeze damage because the material is extremely porous. Moisture seeps into the tiny pores, freezes and expands, and then the surface flakes off as shown below. However, it is possible to use terracotta as a mosaic base provided the mosaic is mounted correctly and the artist understands the limitations of the material.Terracotta flower pots are highly vulnerable to freeze damage because they are soft and porous. The damage could have been minimized by sealing the pot inside and out with a tile and grout sealer. Minimizing Damage To Terracotta Flower Pots
Freeze damage can be minimized by sealing the flower pot inside and out with a tile and grout sealer from a local building material store. Tile and grout sealers are silicone products that plug tiny pores and prevent moisture penetration. They can also interfere with bonding, so we recommend sealing the flower pot AFTER your mosaic is complete. Note that even if you do seal a terracotta pot very well with multiple applications of sealant, it still won’t last as long as a concrete pot would.Concrete Pots Are Preferred
A terracotta pot might be an acceptable base for an abstract mosaic quickly made from random colorful tile, but detailed mosaic designs take more time and effort than that, and they deserve a more durable base. Concrete flower pots and planters are available at most lawn and garden centers, and whatever extra cost is well worth it. A single winter of hard freezes can totally destroy a terracotta flower pot left outdoors. Also terracotta is also easily broken and cracked during normal use.
Sure you might already have terracotta pots at home that you could use for free, but how much money are you saving if the mosaic doesn’t last six months? Once you take the time to mix up mortar and attach the tile, you’ll be glad you took the time to find a concrete base, even if your design is just random tile.Use Mortar Not Glue
The tiles should be attached with thinset mortar instead of glue. White PVA adhesives such as the Weldbond we sell are water resistant when fully cured, but there is a difference between water resistant and water proof. Flower pots are containers full of damp soil, and that means the back of the mosaic will be continually subjected to moisture and acids from decaying organic matter. The acidity of the leach water means that flower pots may be a more extreme environment for mosaics than pools and fountains.
Thinset mortar can also be used to grout your mosaic. Both grout and thinset are powdered portland cement products, but the thinset is stronger and more adhesive. If you are going to have to purchase a powdered cement product to make the mosaic, get the better product (thinset), and use it for everything. You can even reinforce the inside of a terracotta flower pot by plastering it with thinset.