During an experiment the bubble probe is immersed in molten aluminum and hooked up to a capacitance meter.  If a bubble comes in contact with the probe tip the capacitance changes and is recorded, thus allowing me to figure out where bubbles are and potentially how big they are. You see! My capacitance probe is used to detect bubbles in a gas fluxing unit! The Flux Capacitor! Science is great!

  Finding bubbles in molten metals (aluminum and steel that is) is of interest since bubbles do great things when you have a multicomponent liquid and you want to selectively remove a particular component of the liquid.  This happens by way of a chemical reaction between what's in the bubble and what is being removed in the liquid.  In my case, or rather the aluminum industry's case, we need to remove impurities like Na, Mg, and Ca from aluminum.  These impurities come from the primary processing of aluminum and to a greater extent from aluminum recycling.  When aluminum is recycled it is in the form of an alloy, meaning small quantities of other metals have been added to the aluminum to create an alloy with specific properties.  For instance pure aluminum can be strengthened by adding small amounts of Mn (up to 1.25%) and Mg (up to 3.5%) -- this  is the type of alloy used to make beverage cans.  [ The U.S. recycles an amazing 60% of aluminum cans!  And some states, I think MI, recycle 90% of their aluminum cans! ]   Likewise, the aluminum alloys used in airplanes or automobiles have been designed to match the needs of a specific application.   The recycling process is then largely a process of removing these impurities to produce a relatively pure aluminum.  In the gas fluxing process chlorine bubbles are injected into the molten metal and the Cl2 reacts with Na and Mg to form an immiscible liquid or solid which can easily be separated from the molten aluminum. Bubbles can be easily distributed in a large volume of liquid and help mix the liquid which helps remove impurities faster.

Gas fluxing box showing how the 'flux capacitor' can be used to detect bubbles.