Cracked Glass in Stepping Stones

Have you ever created a stepping stone that begins life in great shape but suffers the heartbreak of glass-cracking over time? Recently, we were asked about this problem—what contributes to it and what can be done to avoid it. We consulted several sources, including the folks at DiamondCRETE, and have some suggestions that may help. Here's what we know....

We're embedding glass in concrete and expecting that the two can peacefully coexist. The problem is that glass and concrete—being quite different from one another—expand and contract at different rates. This is something that none of us has control over, and it can certainly lead to cracking. There are, however, steps you can take to reduce the possibility.

Breakage occurs where a glass is most stressed. So the goal is to reduce the stress points in your mosaic projects. Proper scoring and careful grinding are your first lines of defense.

Tiny imperfections and microscopic fissures caused by careless cutting and grinding are the primary causes of glass cracking when imbedded in concrete. These aggravating culprits are caused by:

  • Too much pressure used in scoring ("over-scoring")
  • Small chipping ("scallops" or "clam shells") caused during the grinding or scoring process

Also, when you're choosing glass for use in concrete, try to avoid heavy textures—the variations in thickness make it more vulnerable than a glass with uniform surfaces. And, within your design, avoid long, thin pieces. Instead, modify the pattern, breaking single pieces into smaller, multiple ones that will be more stable.

Remember, by imbedding glass in concrete you're exposing it to additional stress. Give your next masterpiece the best odds you can by scoring and grinding very carefully, and avoiding heavy textures and too-slender pieces. A well-built stone should last a lifetime!

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