By means of a steam generator the bubbles turn out a bit hazy inside. In order to blow hazy bubbles out of your tube, you need to take a tube of large diameter and send some steam into it. The heated air will propel the bubbles upwards. You can do a trick with a steam generator on a glowing desk
. You can fill the bubble with hot air, and when it comes off the desk, it will also fly up. It turns out very spectacular, the audience is thrilled.