What is the usual procedure for selecting a defoamer for a new waterborne coating formulation? For many companies, the procedure appears to be as follows: try the defoamers that you currently use; if these don’t work then try samples in the lab, ask a colleague or friend or, maybe, ask a supplier. This approach makes good sense when working with formulations that are similar, as defoamers will usually give consistent performance in similar formulations. However, when these tried and trusted defoamers don’t work, the chemist has the frustrating task of trying to find a suitable product. There is a truism in England that goes, “if all else fails, read the instructions,” however, defoamers don’t usually come with instructions. Wouldn’t it be nice if they did?
Difficulties in finding a suitable defoamer exist because the performance of each defoamer is affected by the formulation it is used in; change the formulation and the defoamer performance may change as well. Defoamer selection is also one of the last steps in readying a formulation for final use, so the rest of the formulation is already mostly decided, and the defoamer has to work within this formulation. This article presents a brief review of defoamer chemistry and formulation, and describes how defoamer performance is affected by other formulation components in the coating. It also introduces a new range of defoamers that provide consistent and predictable performance relative to one other so that the results of an unsuccessful test can be instructional in selecting the next defoamer for testing with a greater chance of success.