Fireplace crystals are pieces of glass created for use in a fully vented, gas-burning fireplace as a gas log alternative. These small chunks of glass emanate as much heat as traditional logs without all of the messy smoke and soot. Also known as firepit crystals or fireplace glass, fireplace crystals are available in a myriad of colors. People mix fireplace crystals of different colors to create a pleasant visual effect. Some people create color themes for use during specific seasons or holidays or to simulate the look of burning embers.
These crystals are simply broken-up pieces of soda-lime glass, the same type of glass used in bakeware, bottles and older window panes. The manufacturing process for fireplace crystals utilize the "float glass" process. This process involves pouring the molten glass over pools of hot, liquid metal.
One of the major draws of fireplace crystals is their wide variety of colors. Manufacturers can add metals to the raw material mix in order to achieve a specific color during the manufacturing process. Different metals in different concentrations result in different colors; each metal plays off of the others to create the final color of the glass. Iron lends glass a green color, selenium gives it a a red color, and cobalt results in a bluish tinge. Other metals, such as nickel, titanium and silver nitrate, change in color as more of the material is added.
After manufacturing large sheets of soda-lime glass, manufacturers break it up into the smaller chunks popular for fireplace use. The general thickness of the crystals depends on the thickness of the larger sheet of glass they come from. The size of the chunks, however, varies based on the method used to break the glass. Fireplace crystals can be as small as a fraction of an inch (2 cm or less) all the way up to larger rock-sized chunks several inches long (7 cm or more).
No special process are needed to make the glass fireplace safe. Glass melts at 1,500 degrees Fahrenheit (816 degrees Celsius), and fireplaces don't come anywhere near that temperature, staying within 900-1,200 degrees Fahrenheit (482-649 degrees Celsius). Some manufacturers offer tempered glass, but that only makes the glass more difficult to break. Fireplace glass crystals with special reflective coatings are also available. Most manufacturers tumble or polish the chunks of broken glass to make them safer to handle.