Mosaic stepping stones are great first projects, but they don’t have to be cheap and cheesy or dangerous. Keep in mind that if you totally cover the surface of the stone with large pieces of stained glass, it is likely to be slippery when wet. If you leave sharp edges of glass exposed, or allow the grout to erode out from between the glass over time, then your stepping stone is less of a stepping stone and more of a device for cutting bare feet. Both of these problems can be avoided by following best practices and using sound methods.
A Brief Rant
First, avoid the craft kits that have you make a butterfly or some other canned 1970s design by gluing large pieces of pre-cut stained glass onto a stepping stone. Glue will not resist moisture over time, and these kits are the poster child of slippery when wet. They also look exactly like all the other mass-produced stepping stones from China and thus have all the charm of a fast-food wrapper or billboard.
Instead, make something original by pressing your own designs of small tile into wet concrete, and be confident that whatever skill you lack may actually add to the originality and charm of what you make. A homemade stepping stone is supposed to look like a homemade stepping stone and not something made in a Chinese prison factory based on a design first copied in the 1970s.
Glass Tile Is Best
Glass tile doesn’t have any pores, and so water can’t penetrate into it and freeze and crack it. Ceramic materials have lots of pores, and there are tiny cracks in the glazing, so these materials are more susceptible to freeze damage. However, porcelain and dinnerware and other high-end ceramics are a lot more resistant to freeze damage than something like glazed bathroom tile, so they can be used with discretion. Remember, the more soft or crumbly a ceramic material is, the more susceptible it is to freeze damage. Avoid terracotta, glazed ceramic bathroom tile and anything that easily breaks.
Decide Which Method To Use
There are two main methods of making a mosaic stepping stone. It is better to use a mold if you are wanting to use marbles or large stones or other found objects not easily attached to a flat surface.
1. Prefabricated Stepping Stones.
You can cement tile to a plain prefabricated concrete stepping stone purchased from a lawn and garden center.
2. Stepping Stone Molds.
You can press tile into wet concrete in a stepping stone mold or have a mosaic design on contact paper at the bottom of a stepping stone mold and pour concrete on top of that.
Note that both methods require that you mix up a powdered concrete product because you cannot use glue to attach tile to an outdoor or wet mosaic. Instead, you have to use thinset mortar, which is a powdered portland cement with polymers added for enhanced adhesive properties and strength.
Prefabricated Stepping Stones
Plain concrete stepping stones can be purchased from lawn and garden centers. These make great bases for mosaic stepping stones even if you are wanting to press tile into wet concrete instead of cementing the tile to a rigid surface and then grouting later. How is this possible? Easy. You simply spread the mortar on a little thicker than normal, say about 3/8 inch thick, and press the tile into that.
Stepping Stone Molds
Stepping stone molds can be purchased or improvised from ordinary containers such as plastic dish pans and old metal cake pans from the thrift store. Various websites recommend using the nonstick baking pans from your kitchen and even make the claim that you won’t scratch them up, but I wouldn’t go that route. As a general rule, I avoid using anything from my kitchen in my art studio and then returning it to the kitchen, and I’m fairly sure that some people would manage to scratch the pan when they removed the hardened concrete stone. Besides, you can always get old cake pans from the thrift store or use a plastic dish pan or take an old plastic 5-gallon bucket and cut it down with a jigsaw. There is no reason to raid the kitchen when all these other options are available.
Tip: No matter which type of mold you use, make sure you coat it with non-stick cooking spray or petroleum jelly (Vaseline) to ensure that the hardened concrete stone can be removed easily.Sources of Improvised Molds:
A stepping stone mold with some accessories. The pea gravel can be mixed with the thinset mortar to give it strength and bulk.
Sources of Improvised Molds:
- plastic dish pans
- plastic totes
- purchased stepping stone molds
- old cake pans from thrift stores
- 5-gallon plastic buckets cut down with jigsaw
- plastic litter boxes (new or bleached)
- plastic plant trays
- cardboard boxes lined with plastic trash bags
- your spouse’s nonstick baking pans (not recommended)
Two Ways To Use A Stepping Stone Mold
There are two ways to use a stepping stone mold. You need to decide which you will use, and the second is better for marbles and other found objects that aren’t flat like ordinary tile:
1. Put the tile at the bottom of the mold and pour concrete over that.
You can place your tile UPSIDE DOWN in the bottom of the mold and pour the concrete on top of that. The easiest way to keep your tile from moving around when the concrete is poured on top is to put contact paper at the bottom of the mold with the sticky side up. Then you stick your tile UPSIDE DOWN onto the contact paper. This method is recommended if you want a very detailed design because it allows you to get all your tile carefully positioned before you mix up the concrete, which only has a few hours of working life before it starts to harden. Even if your design isn’t very complicated, I wouldn’t attempt it without the use of contact paper. Make sure you add the concrete slowly and gently tap the mold as you go along to make air bubbles come to the surface.
2. Press tile into wet concrete at the top of the mold.
This method is best for mixed-media designs made from marbles and other rounded found objects that couldn’t stick reliably to a piece of contact paper. You simply press the objects into the concrete, and you have the advantage of being able to vary how far they are embedded and to see how the work looks as you go along.
Tip: Wait 30 to 45 minutes before you start pressing objects into the wet concrete. This allows the concrete to firm up a little so that your objects don’t sink to far into it.
Using Thinset Mortar Instead of Ordinary Concrete
Thinset mortar mixed with a little pea gravel is MUCH stronger than ordinary concrete.
Most stepping stone instructions say to use ordinary concrete and often have tips about how to pick or sieve the larger pieces of gravel out of the concrete so that they don’t interfere with the tile or objects you want to embed in the concrete. One of the most significant hazards of doing mosaic work is breathing concrete dust, so if you were going to do this sieving or picking, you would want to do it AFTER you had mixed the concrete up, and that seems like a lot of pointless and difficult work to me.
Instead, I buy thinset mortar, which does not contain gravel, and I mix in small pea gravel in a ratio of 2 parts wet thinset to 1 part pea gravel by weight. For example, to make two small stepping stones, I recently used 8 pounds of wet thinset mixed with 4 pounds of pea gravel.
The pea gravel is needed because thinset mortar slightly contracts as it cures (due to the adhesive polymers), and all traditional portland cement products need and aggregate such as gravel or pea gravel to provide tensile strength.
IMPORTANT TIP: Set some of your thinset aside and don’t mix any pea gravel into it. Use this gravel-free thinset for the layer where your tile will be embedded so that no gravel interferes with the tile as you press it in. First, fill your mold about 3/8 inch from the top with the thinset mixed with pea gravel. Then fill the rest of the way up with the plain thinset. That top layer is where you would press the tile without having to worry about pea gravel in the way. If you have a pattern on contact paper at the bottom of the mold, you would first pour in some plain thinset and then top the mold off with the mixture of thinset and pea gravel.
Tips for Using Thinset Mortar
I have written some instructions for using thinset mortar and some tips for keeping your hands and tools clean while working with thinset mortar.
My instructions in those two links are for doing very detailed work with thinset. Most mosaic projects (such as stepping stones) are a lot more simple. Most of what you really need to know about thinset can be summarized here:
- Wear a dust mask when mixing up thinset to avoid breathing dust, and mix it up outdoors for easy clean up.
- For Versabond brand thinset, we mix 1/4 pound of water per 1 pound of thinset. The package will have manufacturer instructions for how much water to mix in.
- You have about 2 to 3 hours of working time provided you keep the thinset covered when not in use. If you are working in conditions of extremely dry air, such as when the heater or AC is running), then use a humidifier to keep the air moist.
- Do not dispose of thinset in plumbing or drains. It is concrete and can harden underwater.
Cleaning and Sealing
No matter which method you use, you should wait at least 24 hours before removing your stepping stone from the mold.
Sometimes stepping stones made on contact paper at the bottom of a mold will be removed from the mold, and the artist will discover voids between the tiles due to bubbles. Other times, you will see that concrete has gotten between the tile and the contact paper, and so there is concrete on top of the tiles. Both of these problems are easily fixed.
Voids are filled by mixing up small amounts of concrete and dabbing them in. Concrete on top of tiles can be scraped off using a small screwdriver or other steel tool. Use a spray bottle to mist the stone as you work to control any dust.
A few days after your stepping stone has hardened, you should seal it with a tile and grout sealer from a building material store.