You solved it. What happens if a quartz crucible is coated with a graphite crucible?
It doesn't work, but it just adds heat resistance. You get a pretty bad heating effect when you put things in. Of course, if you put it very, very tight, the graphite crucible may crack when heated.
The graphite crucible will burn on an alcohol burner, and the quartz crucible may cause cracks due to uneven heat.
