How to Recycle Glass in a Kiln

Broken glass can be fused together in a kiln.

Recycling glass by turning it into art and decorative pieces is a great way to find uses for broken glass or old glass bottles. The items can be functional dishes, jewelry or sculpture. Glass can be melted in a kiln either in a whole piece or in shards fused together to make multicolored projects. After the glass is melted and fused in a kiln, the glass can be further worked with a blowtorch or other heat source.

Things You'll Need

• Safety goggles
• Hammer
• Paper bags
• Bottle cutter (optional)
• Towel
• Dish soap
• Bottle scrubber
• Rough sponge
• Kiln
• Gloves
• High-temperature mold (optional)
• Kiln shelf paint or other release agent
• Brush

Instructions

1. Soak your glass in hot water overnight. Peel off any labels you might want to keep, then scrub off any glue or residue left behind on the glass using dish soap and a rough sponge. If you are using glass bottles, use a bottle scrubber to clean the inside of the bottles. While organic debris will burn off in the kiln, other debris may lodge in the melted glass and/or give off harmful fumes. Allow the glass to dry completely before continuing.

2. Decide whether you want to use whole glass items, such as bottles, to slump (melted but still recognizable) or if you want to mix your recycled glass together and have it fuse. If you are using whole pieces, see step 4. If you are mixing your glass together, continue on to the next step.

3. Place the glass in a large paper bag and cover with a towel. Put on gloves and goggles. Crush the glass using a hammer.

4. Prepare the kiln shelves or high-temperature mold with shelf paint or another release agent with a brush. If you plan to use a mold, make sure it can withstand temperatures of at least 1600 degrees Fahrenheit.

5. Place the glass on the kiln shelf or in a mold.

6. Heat the glass in the kiln slowly, with the temperature rising at approximately 500 degrees Fahrenheit per hour until it reaches 1200 to 1400 degrees Fahrenheit for slumping, or 1500 to 1600 degrees Fahrenheit for fusing.

7. Soak the glass in the kiln by keeping the temperature constant for five minutes.

8. Open the lid of the kiln for a few minutes to allow the glass and kiln to cool to 1050 degrees Fahrenheit. This keeps the glass from clouding and shattering.

9. Anneal the glass, a process the removes the stress from the glass, by allowing the glass to soak in the closed kiln at 1050 degrees Fahrenheit.

10. Allow the glass and kiln to cool by dropping the temperature to 950 degrees Fahrenheit. Allow the glass to sit until the kiln reaches that temperature.

11. Cool the glass further by turning the temperature down to 250 degrees and allowing the glass to sit in the kiln until it reaches 250 degrees.

12. Turn off the kiln and open the lid. Allow the kiln and glass to cool completely. This may take over twenty-four hours.

13. Remove the glass from the kiln.

Tips & Warnings

• The glass may be worked into shape using a blowtorch or glass furnace after the glass is cooled and removed from the kiln.

• Always wear safety goggles and gloves when working with glass.

References

• Sewanee University: Recycling Art
• My Art Grant: What is Kiln-Cast Recycled Glass?
• Clean Washington Center: Fusing Recycled Glass
• Flat Bottles: Genuine Slumped Glass Bottles