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What are mildew and mold?
The terms mildew and mold typically refer to either fungus or algae, both living, microscopic organisms present in the atmosphere.

What are the ideal conditions for mildew growth?
Fungus and algae thrive in hot, humid, and moist environments, where there is an abundance of organic food source, and periods of darkness.

Why does mildew and mold grow on painted surfaces?
The airborne fungal spores and algal organisms land on the paint surface, and, the flatter and more porous the film, the easier they will be able to adhere to and penetrate the coating.
There, they feed on the organic elements inside of the paint film, such as calcium carbonate, polymer emulsion & additives, as well as organic materials that land on the paint film, from sea spray and wind.

Paints can be made more resistant to mildew and mold growth by:

  • Using a more mildew-resistant resin such as 100% acrylic, as opposed to Vinyl or Styrene Acrylic
  • Decreasing the amount of organic fillers used in the paint composition, providing less food source for the fungus and algae
  • Using resins and additives that create a harder, less porous film making it harder for fungus, algae and airborne organic materials to stay on the film
  • Decreasing the paint’s propensity to leach or “bleed out” the active and inactive ingredients in the paint film
  • Using inactive ingredients (like zinc-oxide) which repel mildew
  • Using active ingredients (like biocides) inside of the paint, that kill mildew on contact

Ulttima Plus Exterior paints are said to contain Mildewguard Technology because:

  • The emulsion paints all use only 100% pure acrylic, mildew-resistant resins
  • The emulsion paints contain zinc oxide, an inactive mildew-resistant ingredient which also serves to cross-link the resins, making a harder film that is less porous and more resistant to both mildew penetration and the leaching of active ingredients inside the film
  • The emulsion paints use a higher concentration of pigments than most paints, and as a result use less of the inexpensive organic fillers than their competitive paints, providing less of a food source for fungus and algae
  • All Ulttima Plus Exterior paints use a revolutionary new encapsulated, controlled-release active biocide from THOR, based on their proprietary AMMETM technology


Conventional biocides are mildew-killing microscopic molecules that are freely dispersed throughout the paint. As the paint film ages or weathers, these biocides come through the surface of the paint film, and kill mildew growing on the surface.

The more moisture the paint film is exposed to, the more and faster these biocides are released, and the more UV rays the biocides are exposed to, the faster they evaporate into the atmosphere.

In the Caribbean, where moisture and UV levels are high, most of the mildew-killing biocides in paints have been exhausted within the first six months to a year after painting.

THOR’s unique AMMETM biocides are encapsulated, or held in organic shields that bind them together inside of the paint and slow down their rate of release, even when in contact with moisture and UV.

As a result, the biocides stay in the paint for much longer, and are released in a controlled fashion over time, providing more mildew-killing protection for longer.