Greengo, but also built-on tobacco, are natural products that can dry out easily. When this happens, they give a less enjoyable smoking experience than when the Greengo or shag tobacco is kept a little damp. Let the stone absorb 2-3 drops of water. You will see that these are incorporated directly into the porous stone. Greengo, but also built-on tobacco, are natural products that can dry out easily. When this happens, they give a less enjoyable smoking experience than when the Greengo or shag tobacco is kept a little damp. Let the stone absorb 2-3 drops of water. You will see that these are incorporated directly into the porous stone.