This results in addition of excess antifoam oil in amounts which may spoil the batch. Another type of device senses the change in capacitance as foam becomes the dielectric in the danger zone in the tank. Again simple relay circuitry is used to signal the antifoam oil controls. Unlike the probes the capacitance detector cannot be fouled. Foam reduction can be performed by use of mechanical foam breakers or the addition of antifoams.
Mechanical methods are a crude approach in the removal of foam.
Therefore, antifoams are extensivly used in industry. Control of foams by oil addition is of large economic importance to the fermentation industry. Excessive foaming causes loss of material and contamination, while excessive oil additions may decrease the product formation. Antifoam oils may be synthetic, such as silicones or polyglycols, or natural, such as lard,soybean, linseed, tall, and rape seed oils. Either will substantially change the physical strusture of foam, principally by reducing surface elasticity.