Not All Mold Resistant Coverings Are The Same

In recent years, the marketplace has been inundated with mold-resistant coatings and products designed to inhibit mold growth. The coatings have been introduced by a number of manufacturers in response to the public’s increasing concern over biological contamination in the home and workplace.

There are no universally accepted standards or specifications for tests used to determine the efficacy of mold-resistant coatings on the market. As such, industrial hygienists and mold remediation professionals cannot make an accurate competitive comparison, and must base coatings recommendations on their own experience and/or the results of tests made available by the coatings manufacturers themselves.

The proliferation of mold-resistant coatings and lack of universally accepted testing practices have combined to create a common misconception that all coatings perform equally. In fact, the exact opposite is true since improperly engineered coatings can serve as a food source for mold spores – which in turn – increases the opportunity for mold growth. All too often, specifiers and end-users alike have been disappointed by coatings failures.

A four-week study was conducted for the Foster business by independent microbiological laboratory Aerotech Laboratories, Inc. The study examined the efficacy of three mold-resistant coatings: Foster® 40-20™ Fungicidal Protective Coating, Fiberlock IAQ 6000™ Mold-Resistant Coating, and Sentinel® 24•7™ Multisurface Coating (White). The study involved the most stringent test method known to be available: “ASTM D5590-00 Standard Test Method for Determining the Resistance of Paint Films and Related Coatings for Fungal Defacement by Accelerated Four-Week Agar Plate Assay.” Test results compared the three products’ ability to inhibit growth on the coating surfaces under identical conditions, which included a seven-day water leaching study.

The study showed that the Foster 40-20 coating allowed no growth of mold on its surface while the Fiberlock IAQ 6000 coating and Sentinel 24-7 coating both exhibited mold growth on their surfaces. In the final analysis, the Foster 40-2- coating demonstrated superior protection when tested by an independent laboratory using the ASTM D5590-00 test methodology.

Mold and mildew are naturally occurring, ubiquitous organisms found throughout indoor and outdoor environments. The organisms will grow with the right combination of moisture, mold spores, temperatures and food sources. Whenever moisture combines with a food source, these organisms can start to grow and spread within 24 to 48 hours – and will grow exponentially given the right conditions. Many building construction materials are excellent sources for these organisms, especially mold.

If mold contamination does occur, addressing water intrusion and humidity issues are key factors in solving the problem. Another solution commonly used is the application of mold-resistant coatings over the affected areas during remediation or construction to prevent re-occurrence. By applying the proper coating, end-users and specifiers can help protect nutrient sources, such as wood and drywall, from mold growth if (and/or when) moisture does accumulate.

The failures of some mold-resistant coatings in recent years can generally be attributed to:

• Misperceptions: Many end-users and specifiers believe that all mold-resistant coatings are created and perform equally.

• Lack of standard tests: No industry-accepted standard tests and performance requirements exist to compare the efficacy of mold-resistant coatings on the market. As such, coatings end-users and specifiers must rely on their own experience or the test results made available by coatings manufacturers when choosing products.

• Varied conditions: Many users and specifiers are unsure whether a mold-resistant coating application actually inhibited mold growth after it was applied, or whether the problem was avoided because conditions never existed for mold growth (or re-growth). In other words, the efficacy of the coating will often go unchecked unless a mold problem is identified or, in the case of mold remediation, rediscovered. The problem is exacerbated because mold growth often occurs in areas that are difficult to access, e.g., wall cavities, HVAC ductwork, etc.

Given these factors, the Foster business commissioned Aerotech Laboratories, Inc., a leading commercial Indoor Air Quality (IAQ) laboratory, to study the efficacy of Foster 40-20 Fungicidal Protective Coating in an environment most conducive to mold growth. Aerotech Laboratories also examined the efficacy of two competitive mold-resistant coatings and compared the three products’ ability to inhibit growth on the coatings’ surfaces under identical conditions, which included a seven-day water leaching study.

To determine the efficacy of the coatings under conditions in which mold and mildew are most likely to occur, Aerotech Laboratories performed “ASTM D5590-00 Standard Test Method for Determining the Resistance of Paint Films and Related Coatings for Fungal Defacement by Accelerated Four-Week Agar Plate Assay.” The test was conducted using mixed inoculums of mold. It also uses a potato dextrose agar, which is an excellent mold food source and one that ensured continued growth of mold on the media surface for the duration of the study.

Under the ASTM D5590-00 test method, the samples were prepared and applied according to the manufacturer’s instructions and recommended coverage rates. For the test, accelerated aging of samples was done under specified conditions. For testing purposes, samples that are not water leached are referred to as “un-aged” samples.

To conduct the tests, the coated samples were cut into one-inch squares and placed in Petri dishes containing the agar. Next, the dishes and samples were inoculated. Unlike other test methods, ASTM D5590-00 exposes samples to extensive and continued mold growth by spreading viable mold spores equally over both the sample and potato dextrose agar. The dishes were then placed in a controlled environment to promote mold growth for 28 days. To test mold resistance after severe water exposure, the samples were prepared in the same way as un-aged samples, then submersed in de-ionized water for seven days prior to exposure in the Petri dishes.
Growth on the sample itself was given a rating from 0, being no growth observed, to 4, being heavy growth observed.

For un-aged samples, the Foster 40-20 coating exhibited excellent resistance to mold growth when tested under the harsh conditions of ASTM D5590-00. Fiberlock IAQ 6000 coating allowed heavy mold growth on its surface. Moderate mold growth was noted on the Sentinel 24-7 coating surface.

Water-leached tests show that the Foster 40-20 coating maintains its fungicidal properties even after severe water exposure. Under these test conditions, the Fiberlock IAQ 6000 coating allowed heavy mold growth. Also under these conditions the Sentinel 24•7 coating allowed moderate mold growth.

Results of the four-week Aerotech Laboratories study show that not all mold-resistant coatings exhibit the same level of performance under rigorous test methods. It also illustrates that Foster 40-20 Fungicidal Protective Coating has excellent mold resistance even in wet test conditions. In the final analysis, the study demonstrates the need for industrial hygienists and end-users alike to carefully research the capabilities of the mold-resistant coatings on the market and to evaluate the track record of the companies that supply them.