When making hot molten glass beads, a tremendous amount of stress is put on the glass. These stresses remain in the glass after the bead has been made. To eliminate the stress on the glass, the beads are annealed inside a hot kiln. You can also put them in a crock pot in sand or vermiculite, but a kiln is the very best way to anneal your beads. To start the annealing process, you keep your newly formed beads on the metal rod or the mandrel, place inside a kiln with several beads - not touching - and start heating slowly until it reaches 940 degrees for 30 minutes. Then the temperature is slowly dropped to 600 degrees where the kiln is then turned off. The bead is allowed to reach room temperature and then can be removed from the mandrel. These annealed beads are incredibly tough. When beads are not annealed they can break or crack. They can break or crack years after the bead was made. Different glasses anneal at different temperatures. This is why you cannot mix glass rods when making a lampworked glass bead.