Volume 6, Issue 5 (May 2009)
Antifoaming and Defoaming in Agricultural Tank Mixes: Revisiting, Revising, and Reviving a Method
The foam that is generated in agricultural tank mixes is of great concern because this foam can cause problems such as slow mixing and worker exposure. Antifoaming and defoaming agents are used to control this foam. Developing a reproducible test that accurately predicts the real world performance of these products has been difficult. Several methods are briefly reviewed. An ASTM method has been developed and established. However, this method intuitively is difficult to translate into real world performance. An older possible method has been shown to have obvious and significant problems. Several new modifications to this older method are proposed as a means of overcoming the problems and measuring the performance of products. The proposed method involves a large, polypropylene beaker that is charged with a foaming solution. The solution is stirred and foam is generated using an air sparge and a sparge stone defined in another current ASTM method. Defoamer is added to the foam and the time required for the foam to collapse and to reform is measured separately. The way the foam disintegrates and redevelops can also be observed and recorded or described. Statistical data indicate that, using this method, differences between the performances of various defoaming/antifoaming agents can be determined. The differences are reproducible enough to identify performance differences that will be appreciable in the field. As a result, quantitative and qualitative data may be generated using the proposed method. Also significant is that the method separates antifoaming and defoaming into discrete measurements. This separation of the two measurements provides a better measurement for how a product will perform in the field relative to other products. Calculations resulting in new terms are proposed as a means to create a scale that will allow direct comparison of the performance of various antifoams/defoamers.