OS‑431 Defoamer is a non-silicone defoamer that is particularly well suited to controlling foam in aqueous dry film developing solutions and stripping solutions. OS‑431 is unique because it is water soluble at the concentrations at which it is normally used for defoaming solutions. This means that unlike many other defoamers, no oily film will be left on parts processed in solutions defoamed with OS‑431. Furthermore, any OS‑431 that might be carried over on the parts into subsequent rinse tanks will completely dissolve in the rinse water, thereby preventing oily films from accumulating on the surface of the rinse water. OS‑431 is used at low concentrations. Therefore, it is economical to use.