Paint formulations contain standard industrial biocides for in-can preservation and stability. However, in-can preservatives do not necessarily offer dry film protection, as the dynamics of microbial protection change when the paint film dries. Furthermore, EPA registrations and regulations dictate the kind of antimicrobials that can be employed for dry film protection and claims that can be made from the use of these antimicrobials.
Formulating paints that have long-term dry film protection is challenging. For outdoor applications, variations such as the direction a painted surface faces can create dramatically different responses to how the paint is attacked by algae and fungus. A variable such as this, coupled with the wide variety of climate and geographic variables to which any paint product is subjected, increase the problem manufacturers face when attempting to warrant paint performance and durability. While indoor paints are typically subjected to narrower environmental fluctuations, variations in moisture, temperature, cleanliness (i.e., the degree of microbial infestation), age of construction and the type of substrate on which the paint is applied can all affect paint film integrity.