The easiest way to make colorful stepping stones was taught to me by concrete artist, Terri Ryan, who make many, many indoor and outdoor ornaments from concrete. Without a mold, she simply adds a thin layer of concrete to the top of a purchased round stepping stone and stamps a circle or two into the concrete before it sets. She then uses stain for concrete floors--which comes in small bottles and bright colors--to paint her stones. The tops of the stones are very smooth and rounded (no edges to break off) and look really nice in her garden. The stain fades over time, so it needs a touch-up every 2 to 3 years.
Unfortunately, it's difficult to find round stepping stones these days at the large home improvement and hardware stores. So I decided to make my stepping stones from scratch. I was lugging home a 94 lb. bag of Portland cement anyway, so I had plenty to make a whole army of stones.
Step 1: What You Need
94 lb. bag Portland cement
50 lb. bag of masonry sand (enough for six stepping stones)
12-inch plan saucers or stepping stone molds
plastic bucket or trough
cans from the recycling bin, various sizes
long stake for stirring and leveling
cooking spray or petroleum jelly
cement stain (Smith's Color Floor comes in bright primary and secondary colors)
1 yard of 1/2-inch hardware wire
For an impromptu work surface, set up two saw horses, place a large piece of scrap plywood or boards on top, then cover with large garbage bags.
Step 2: Mixing the Concrete
Apply cooking spray or Vaseline to the bottom and sides of the saucers. Wearing a good dust mask and measuring with a 14-oz can, mix 6 cans of masonry sand with 2 cans of Portland cement. Stir with a stake or mix with a gloved hand until the sand and cement are completely combined. Add 2 cans of water and stir until well blended. Add additional water until concrete is like a thick batter, somewhere between crumbly and runny. Dump concrete into saucer until it is half full, pressing into corners.
Step 3: Strengthening
To strengthen the stepping stone, cut 1/2-inch hardware cloth to fit inside the mold without touching the sides. (I didn't have any on hand so I layered pieces of drywall tape instead.) Center the round piece of hardware cloth on the cement, then fill to the top with concrete. To eliminate air bubbles, tap the mold against the table several times, or set mold on a running washing machine. Level off the top with the edge of the stake, moving it in a side to side sawing motion as you draw it across the top of the mold. Use paper towels to absorb excess water that floats to the top.
Step 4: Stamping and Curing
After about an hour the concrete should be firm enough to imprint circles about 1/4-inch deep with the tops of cans. After about 6 to 12 hours (depending on the weather), place a board or tray on top of the mold, invert each stone onto the board, and carefully remove the saucer. Cover with plastic for 24 hours, then gently round the edges of the stone with a file. Cover the tones again in plastic to keep moist for at least five days to cure. The longer the drying time, the stronger the concrete, so always keep concrete out of direct sun while it's curing.
Step 5: Staining
Remove the stepping stone from the plastic. Mix stain with distilled water and apply with a brush to color in areas of the stone. For really vibrant color, use the stain straight from the bottle. The colors can be mixed, but for more vibrant green, buy green.