Hi Rachel,

there are two ways of defoaming. The first is the most obvious by using an incompatible oil like silicone or mineral oil based. The second one is by molecular defoaming. They could also be combined as the method of defoaming is different.

Important factors are the type of surfactants you are using (an-ionic, non-ionic etc.) as well as the pH (higher pH, more foam and harder to control as most oils are not stable in pH above 10 and surfactants become more active).

Molecular defoamers are in cleaning mostly known as cloud point defoamers. In an aerosol,there are more factors. First, you have no control over the cloud point (RT application, there is no heating element in the can like in your washing machine). key here is temperature independent molecular defoamers.

The specialist to talk here to would be Rick Theiner (cleaning specialist from the Tomah3 group) and or Charlie Hegedus (surfactant specialist and defoamer specialist) at Air Products & Chemicals inc. They supply molecular defoamers as well as oils in the paint additives department under the Surfynol and EnviroGem tradename. Check the following link: http://www.airproducts.com/surfactants/productByFunction.asp?p_func=molecular%20defoamer There is a whole bunch of molecular defoamers which are temperature independent, pH stable, with solvent, no solvent, on a solid carrier etc.

Further more, I would check your valve system as well. Try not to use a house with a VPH (at least that's what they call it in Germany, its the small hole in the house inside the can to add more gaseous material when spraying for a finer spay image) and check your nozzle (not too many channels) diameter and the channel formt he tip tot he nozzle should be as short as possible to prevent after foaming (use the quarter inch nozzle caps).

Most of the prevention is done mechanical, the last bit with formulation.

I hope I used the correct English phrases, I am used to Dutch and German terminology.

Hope this helps, else specify a little further and contact me.