How does the glassblower adjust the thickness of the sleeve of a pipe?

If this means the clear that will go over a color or graal, or alien skin, this is chosen by the blower.  The more clear, the more it seems to be under the glass.

As the blower pulls the pipe out the glass will get thinner as it is pulled, the diameter also shrinks.  Thicker glass takes more heat to work.

What techniques can you use a lathe for in glassblowing?

Really you can use a lathe for many techniques that a blower can do by hand.   The lathe allows a blower to work more effortlessly giving them the ability to make a headier piece of glass.

The lathe is a must for a clean glass cup, by hand it will not be a clean

See glass lathe here.

What is an inline perc?

An inline is pretty simple. It is a perc that has slits on the top or bottom with a grid pattern that runs the length of the water pipe.  To see all or percs visit our glass terms blog