Frit is nothing more than small pieces of glass. Generally, they are sorted by size and used in a variety of ways, the most common of which are kiln casting, pate de verre, or as a design element on sheet glass.
The easiest way to obtain your own frit is to buy it. Tested compatible frit is available from both Bullseye and Uroboros. It comes in a number of different sizes, ranging from powder to chunks as large as 1/4" (6 mm).
If you want to make your own frit, there are a number of techniques. Several are described below.
• Using a hammerFor this approach, place the glass to be used between several pieces of newspaper and strike with a hammer until the pieces reach the desired size. This method is crude but effective. Make sure you wear eye protection. Wear a mask if significant dust is produced.
• Tack fusingPlace the glass in the kiln. One arrangement that works well is to heap smaller chips of glass on a larger sheet. Heat until the glass tack fuses — around 1400 degrees F. Once the glass has fused, turn off the kiln, remove the glass (use gloves and tongs — steel fireplace tongs work well), and drop immediately into a bucket about 2/3 full of cold water. The shock will crack the glass into many small pieces. Glass broken this way will be in relatively large chunks. If you want finer pieces, you can use the hammer technique described above to break it down some more.
• Melting in a crucibleThis technique requires more caution than the first two. Place the glass in a crucible, a ceramic container made for withstanding the heat of the kiln. Heat it to around 1700 degrees and soak to allow the glass to melt.
Then turn off the kiln and use tongs to remove the crucible. (Wear gloves and eye protection and take special care.) Slowly pour the molten glass into a bucket of cold water. The glass will break into finer particles than in the tack fuse approach discusses above. Make sure you return the crucible to the kiln and let it cool slowly to prevent thermal shock.
• Pipe-crushingObtain two hollow pipes, one slightly larger in diameter than the other so that one pipe fits inside the other. Close off one end of the smaller pipe, fill it with rocks or similar heavy items, then close off the other end.
Now place the larger pipe upright on a hard surface like cement and fill it part of the way with the glass you want to break. Slide the smaller, heavy pipe into the larger one, letting it drop full force onto the glass. (You will probably need a second person to help you hold the larger pipe.) Raise the smaller pipe and drop again and again until you are satisfied with the size of the particles. If you use this technique, wear eye protection and a mask or respirator to protect you from the silica dust. Also, you may want to use a magnet to extract any metal chips that may be caught in the frit.
• Frit-making machinesIt is possible to buy frit-making machines, called "glass crushers." Alternatively, you can rig up your own machine using a garbage disposal, heavy duty blender, or similar item. Boyce Lundstrom's Advanced Fusing Techniques describes a crusher built from an old garbage disposal and a large steel drum. Kervin and Fenton'sPate de Verre and Kiln Casting of Glass also has information about building your own frit machine.
If you make your own frit, you will probably want to separate it into sizes and store it in jars or plastic bags until needed. You can separate the glass manually or you can use wire mesh screens, which are available from ceramic supply stores.