As you probably know, I have made quite a few stepping stones using stained glass for the design. In order to get the peices of the design to stay where you want them, 1st, spray your mold (I use W-D40)
then cut a piece of contac paper the exact shape of your mold. (Sticky side up.
2. I place the glass pieces (upside down) on the contac paper. I pour in about an inch, to inch & a half of the concete.
3. I cut a piece of chicken wire leaving at least an inch from the outside edge of the mold.
4. Pour the balance of the cement over the chicken wire. You need to shake or vibrate the mold gently or rap the sides sharply to bring the air bubbles to the top. You don't want air holes on top of your stone.
After 24 hours you can remove the stone by turning the mold upside down. Then you can gently clean off the design with a wet sponge leaving a very smooth surface. Let it dry undesturbed for another 24 hours, spraying with water every few hours. After they are completely dry, about a week, I brush on a concrete sealer. Useing the chicken wire for reinforcement prevents cracking. I make mine 2-21/2" thick, leave them out all year and have never had one crack.
