I wouldn't be concerned so much with glass shrapnel, as with almost molten wax spraying out. Have you ever opened up a lava lamp? The bottle is capped with an

I wouldn't be concerned so much with glass shrapnel, as with almost molten wax spraying out. Have you ever opened up a lava lamp? The bottle is capped with an old-fashioned pull-off bottle cap. I guarantee that if anything goes pearshaped, it'll be the integrity of that cap.