by Juanita Canzoneri
Making mosaic art can get expensive. But creating beautiful artwork doesn’t have to mean spending a fortune. In our Mosaic on a Shoestring series, we’re exploring creative ways to save money, use what we already have, and make the most of our materials.
In our first installment, we looked at wood as a mosaic base for indoor mosaic pieces. This time, we’re heading outdoors and exploring three more possibilities: rocks, terra cotta pots, and concrete surfaces.
The key to a successful outdoor mosaic is choosing a base that can handle the environment. Before you start gluing, take a little time to make sure your base is sound, clean, and suitable for the job.
Rocks: Nature’s Ready-Made Canvases
Rocks are a favorite inexpensive bases for outdoor mosaics. They come in all shapes and sizes, and their natural forms can inspire everything from simple garden decorations to more elaborate artwork.
You can often find suitable rocks in your own yard or through landscaping businesses. If you need a larger quantity, a landscaping supplier may be a better source than collecting them one at a time from your environment.
Start with a clean, solid surface
Before using a rock, wash it thoroughly and let it dry completely. Dirt, dust, and moisture can interfere with adhesion.
Look for rocks that are:
- Solid and stable
- Free of deep cracks
- Not flaking or shedding loose material
- Large enough to support the mosaic you have in mind
A rock that looks beautiful but is already breaking apart is not a good foundation for a long-lasting mosaic.
A note about sourcing
If you’re collecting rocks, be mindful of where they come from. Avoid taking rocks from places where removal is prohibited or could damage the environment. If you need a lot of material, landscaping businesses can be a practical and responsible source.
What adhesive should you use?
For outdoor rock mosaics, silicone is often a good choice, especially when working with small, irregular surfaces. A suitable exterior-grade silicone can provide flexibility and help accommodate the movement that outdoor materials experience.
Always check that the adhesive is appropriate for your specific materials and intended use. We’ll talk more about adhesive choices as the series continues.
Terra Cotta Pots: A Little Preparation Goes a Long Way
Terra cotta pots are another affordable way to create outdoor mosaics. They’re easy to find, come in a variety of shapes and sizes, and make wonderful garden accents.
But before you start decorating, it’s worth taking a closer look at the pot itself.
Choose your pot carefully
For a mosaic that you want to last, I recommend starting with a new, purchased pot. Older, used pots may have damage or other issues that aren’t immediately visible.
Look for a pot that is:
- Free of cracks
- Not crumbling or deteriorating
- Structurally sound
- Suitable for the type of outdoor use you have in mind
Is the pot porous?
Terra cotta pots can be porous. This can be good for gardeners or plants, but doesn’t create a long-lived mosaic base.
A simple way to check if a pot is porous is to place a few drops of water on the pot. If the water quickly soaks in, the surface is porous. If it sits on top, the surface may be less absorbent. It could be that the item was fired to a higher temperature or has already been sealed in some way.
Sealing the surface
Depending on the pot and the adhesive you plan to use, you may want to seal the surface before beginning your mosaic. You can use a commercial terra cotta sealant or create your own sealant using Weldbond and water. Weldbond is the only product I know that will work with this method.
Mix 1 part Weldbond with 5 parts water. Using a clean paintbrush paint the mixture onto all the surfaces of your pot and allow pot to absorb all the liquid you put on.
Repeat this process until the mixture no longer soaks into the terra cotta.
Once everything has completely dried, you’re ready to begin your mosaic knowing that, whatever happens to this pot in the future your artwork will be as long lived as the pot.
Adhesive choices
For outdoor terra cotta mosaics, GE II silicone or another suitable exterior-grade silicone is often a good option. As always, check the product instructions and make sure the adhesive is appropriate for both the base and the materials you’re attaching.
A little preparation here can save you a lot of tears later.
Concrete: A Strong Base for Outdoor Mosaics
Concrete is another excellent option for outdoor mosaics. You can work on vertical surfaces, such as walls, or horizontal surfaces, such as stepping stones.
Cement and concrete: What’s the difference?
I often use the words cement and concrete interchangeably, but they’re not at all the same thing.
Think of it this way:
Cement is like flour. Concrete is like bread.
Cement is one of the ingredients used to make concrete. Concrete is the finished mixture of cement, aggregates, and water.
For our purposes, the important thing is that we’re looking for a sound concrete surface to work on.
It’s a versatile material, but the condition of the concrete is especially important.
Check the condition of the concrete
Before applying a mosaic, make sure the concrete is in good condition. It should not be:
- Flaking
- Crumbling
- Deteriorating
- Covered in loose material
If the surface is already breaking down, your mosaic will not have a stable foundation. This way only leads to heartache and frustration.
Clean the surface before you begin
Concrete can have surface grease or other contaminants that interfere with adhesion. TSP (trisodium phosphate) can be used to remove surface grease, leaving the concrete cleaner and better prepared for your project.
As with any cleaning product, follow the manufacturer’s instructions and use appropriate safety precautions.
Thinset is the go-to adhesive
For outdoor mosaics on concrete, thinset is generally the adhesive of choice. It’s designed for use with masonry and other suitable surfaces, making it a strong option for projects that need to withstand outdoor conditions.
We’ll be talking more about thinset in Session 3, so for now, just remember: when you’re working on concrete, thinset is an important material to have in your toolkit.
A note about stair risers
Stair risers can be tempting places to add a mosaic, but think about how the stairs will be used.
If you’ll be using a snow shovel on those stairs at any point, I recommend leaving the risers alone. A shovel can catch on the edge of a mosaic and damage the artwork—or the shovel. (This advice comes from a friend who had the heartbreak of having to remove his damaged mosaic stair risers.)
Sometimes the most practical design choice is knowing where not to put a mosaic.
A Few Final Thoughts
Outdoor mosaics can be a wonderful way to turn ordinary materials into something special. Rocks, terra cotta pots, and concrete all offer opportunities to create beautiful artwork without spending a lot on a traditional mosaic base.
The most important thing is to start with a sound foundation. Clean your materials, check their condition, and choose an adhesive that is appropriate for the job.
And remember: saving money doesn’t mean cutting corners. It means making thoughtful, and creative, choices about where to spend your money—and where you can use what you already have.