How to Recycle Glass in a Kiln

Updated April 17, 2017

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, jewellery or sculpture. Glass can be melted in a kiln either in a whole piece or in shards fused together to make multicoloured projects. After the glass is melted and fused in a kiln, the glass can be further worked with a blowtorch or other heat source.

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.

Decide whether you want to use whole glass items, such as bottles, to slump (melted but still recognisable) 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.

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

Prepare the kiln shelves or high-temperature mould with shelf paint or another release agent with a brush. If you plan to use a mould, make sure it can withstand temperatures of at least 871 degrees Celsius.

Place the glass on the kiln shelf or in a mould.

Heat the glass in the kiln slowly, with the temperature rising at approximately 260 degrees Celsius per hour until it reaches 649 to 760 degrees Celsius for slumping, or 816 to 871 degrees Celsius for fusing.

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

Open the lid of the kiln for a few minutes to allow the glass and kiln to cool to 566 degrees Celsius. This keeps the glass from clouding and shattering.

Anneal the glass, a process the removes the stress from the glass, by allowing the glass to soak in the closed kiln at 566 degrees Celsius.

Allow the glass and kiln to cool by dropping the temperature to 510 degrees Celsius. Allow the glass to sit until the kiln reaches that temperature.

Cool the glass further by turning the temperature down to 121 degrees C and allowing the glass to sit in the kiln until it reaches 121 degrees C.

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

Remove the glass from the kiln.


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.

Things You'll Need

  • Safety goggles
  • Hammer
  • Paper bags
  • Bottle cutter (optional)
  • Towel
  • Dish soap
  • Bottle scrubber
  • Rough sponge
  • Kiln
  • Gloves
  • High-temperature mould (optional)
  • Kiln shelf paint or other release agent
  • Brush
Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Native of Colorado and single mom, I’ve been designing websites for over 16 years. I am fluent in HTML, CSS and web standards. I work with Wordpress, Drupal, and other content management systems. I have extensive social media experience and have been integrating analytics, web sites and social media for years. I have designed for non-profits, corporations and artists. Give me a text editor and code to write and I’m content.