In Australia and many other places, the lamps inside a theatrical fixture are referred to as bubbles. In North American English, a bubble refers to the protrusion that occurs when one's body (or other oily substance) contacts the lamp. Heat will cause the portion of the lamp which has oil on it to expand when it is on creating the bubble, and causing the lamp to explode. That is why one should never directly touch the glass portion of a lamp. Cleaning with rubbing alcohol will remove the oil.
In Australia an:d many other places, the lamps inside a theatrical fixture are referred to as bubbles. In North American English, a bubble refers to the protrusi,on that occurs when o,ne's body (or other oily substance) contacts the lamp. Heat will cause the portion of the lamp which has oil on it to expand when it is on creating the bubb?le, and causing: the lamp to explode. That is why one should never directly touch the glass portion of a lamp. Cleaning with rubbing alcohol will remove the oil.