I know there has been plenty of discussion in the forums about working with Terra, but here's my little tutorial on how I've been encasing it:
Step 1: Ask the Forces of the Universe to set the wind blowing in the right direction...
Tip: The most important thing I've discovered about this glass is it likes to be worked quickly, because extended heating fades out the colors.
Step 2: I put one layer of Terra straight down on the mandrel as the base bead. I get it really hot, until I see the surface start to turn transparent and get a "shimmer" like what some people see when heating raku. The Terra glass at this point is so hot that it balls up and makes those irksome pointy ends along the mandrel.
Step 3: I take it out of the flame and gently marver it into a cylinder shape to get rid of the pointy ends. I don't put it back in the flame after marvering. I let it continue to cool until a brown color starts to appear, then I gently waft the bead in the end of the flame or just under the flame so the heat is light, and watch for the dark brown color to propagate across the bead.
Wherever dark brown develops on the bead, the color will end up more intense with dark reds, blues and purples. Where light brown forms, the colors will end up in the lighter pink/yellow range. If the desired dark brown does not show up and I'm only getting wisps of light brown across the bead, I reheat the whole thing and start from the beginning. I super-heat it, marver it, and watch for the brown again. I've noticed that Terra can get "tired" after too many re-tries (so can I !!! ). If this happens I take a deep breath, then run a Terra stringer around the bead giving it a fresh layer on top.
Step 4: When I'm satisfied with the brown colors, I take my Terra base bead out of the direct flame and encase it. I do my best not to reheat the Terra base too much which would fade out the dark brown color. After I apply the encasing glass, I marver and shape it just like I would with any normal bead. However, by the time I'm done with my shaping, I cool the bead down a little and look at it and these magnificent colors have magically appeared!
Practice is really the secret to this glass. And the wind blowing in an auspicious direction of course.