I just got this lamp, it was stored in my grannys stuff, and I think it hasn't been used in a while. When I heat it up, it just kinda sits at the bottom for a while. After a while, it moves up to the top in one blob, and stays there. What do I do to get the lava moving? Attached is a picture of the exact lava lamp, the pictures not too great but you can see the lava sitting at the top of the lamp.