[Venbead]

Here's the chemistry lesson from the right brain glass working therapist. keep in mind I got a C in chemistry but this is how i understand it:
When you keep a piece hot enough the large and small molecules move around freely and stay well mixed. if the piece is not kept hot enough and parts of it begin to cool the larger molecules can no longer move freely and the smaller molecules begin to pool and separate out into similar materials. you will get crystal growth in a random and unorganized fashion. this is phase separation.(think baby poop, veiny beige lines and devit) what you want to do is keep the whole piece white hot and then remove it from the flame.
to strike you can either pop it in the kiln and let the kiln do the work or bring it back into the flame once it has reached the transformation temperature (count to 40) bring it into the outer most reaches of the flame to strike and turn very slowly. you want crystal growth in an even and organized fashion around a central nuclei (think snowflake)
do the flame striking too quickly and your crystal growth will be uneven and you will get striations in the glass ( phase separation) and this will cause muddy colors. when you begin to see color develop remove it before you are satisfied because more crystal growth will occur when you anneal the piece.