Things You'll Need
Boots or other closed-toe shoes
10-foot length heavy industrial paper or painter's tarp
Wooden block, stump or concrete block
Sheet of tempered glass such as a used shower door
Thin work gloves
Eye protection such as goggles or safety glasses
Hammer or rubber mallet
Tempered glass is a type of glass that, unlike standard glass, shatters into small, primarily blunt, pieces when it breaks. It is manufactured at different temperatures than standard glass and is used as safety glass in shower doors, car windshields and on table tops. Apart from its traditional uses, tempered glass is also a popular tesserae used in contemporary mosaic art. However, to use the glass correctly, you must intentionally shatter it with a blunt instrument.
If done properly, the process is safe and easy. Only adults should break the glass, and only after taking the correct safety precautions.
Dress in a long-sleeved shirt, long pants and closed-toe shoes or boots.
Spread a 10-foot length of industrial paper or tarp over a hard, level surface such as a concrete patio. The surface should be well away from children and pets and out of the path of foot traffic.
Place the concrete block, stump or wooden block on top of the paper or tarp close to the edge. It will be used as a rest for one end of the glass while the break occurs, so be sure to position it so that the glass will fall on the paper or tarp.
Rest one end of the unbroken sheet of tempered glass on top of the stump or block. Place the other end on the ground on top of the paper or tarp. If the stump or concrete block is 12 inches high, the glass will rest at an approximate angle of 5 degrees.
Put on thin work gloves and eye protection, such as safety glasses or goggles.
Check to make sure the surrounding area is clear. Stand at the elevated end of the glass and raise the hammer or mallet overhead. Gauge the area where the hammer will come down on the glass, and briefly turn your face away from the glass while striking hard with one swift blow.
Stand aside. The properties of the tempered glass will cause it to continue to break for up to 30 minutes. Expect small popping noises and the occasional piece that will jump off of the paper. The glass will break into small, loose pieces and larger, fragile pieces that are cracked but still remain together.
Gather the glass carefully, after the popping noises have ceased. Gently pick up the largest pieces first. Place them into plastic containers. Place lids on the containers. Then, gather the smaller pieces by sweeping them into a dust pan. Place the smaller pieces in separate plastic containers and seal with lids.
Fold up the paper or tarp and dispose of it. Thoroughly sweep the area where the break occurred, taking care not to leave any broken glass behind.
Try to retain as many of the large pieces of glass as possible. They will sometimes shatter into smaller pieces as they are gathered, but the small pieces can also be used, so put those in a separate container. Work gently at all times, taking care not to jar the containers.
Never process tempered glass while alone. Regardless of safety precautions, even broken tempered glass can be dangerous. It is always a good idea for someone else to be around in case of accidents.
While breaking the glass in the above-described procedure causes it to fall into a confined area, there is the rare chance that a small piece might fly astray. It is crucial to keep children, pets and any spectators well away from the area during the actual act of breaking the glass. After the procedure, take care that all stray glass is removed from the area.