Originally Posted by mattathayde
glaze is glaze, you have high fire and low fire, high fire takes higher temp to apply, gives nicer colors (iirc) and is more durable, low fire take lower temp to apply, gives more pastel colors (iirc) and is not as durable.
its probably high fire, glaze is just a colored glass basically, nothing special
o edit, its probably a food safe grade of glaze, i dont remember off hand if food safe is the common version or not (not really knowledgeable in ceramics just a general knowledge from doing a little of it and from it being in my department here at school)
It's been a while, but I have taken ceramics courses in the past.
I remember that there are certain glazes that are not dinnerware safe because of what is used in the glaze.
From what I did (which was very beginner) the heat of the kiln didn't effect the glaze color. The kiln just melts the glass glaze onto the pottery at the correct temp.
That said, I doubt if they would use any bad types of glaze for a hookah bowl.