Swimming pool chemistry: A term used to describe surface foam on your water, esp in spas/hot tubs. Foaming is caused by high TDS levels working in combination with soft water and oils. Certain low grade algaecides can foam when added to pool or spa. Use enzymes for foam control.
Found on http://www.1st-direct.com/acatalog/Chemical_Glossary.html
Foaming is the process of producing a cellular plastic by using foaming agents. A foaming agent is a material mixed with or dissolved in a plastic to make it foam. It includes expanding agents that produce gas on heating – such as easily volatile solvents – or chemical blowing agents that produce gas by thermal decomposition. Weight reduction i Found on http://www.blowmachines.com/glossary1.htm