There can be different explanations of why this happened. The grout may have been washed too soon or too much during the cleaning process, causing pigment to be removed from the grout. Or, the grout powder may not have been dry-blended before mixing in order to avoid color variation.
ASTM G21 is an industry standard that uses an intensive testing protocol for determining if fungi, including mold and mildew, can grow on a polymeric material. MAPEI uses a third-party lab and the ASTM G21 standard for testing the antifungal effectiveness of MAPEI products containing polymer that incorporate BioBlock technology. The ASTM G21 test uses a mix of mold and mildew spores commonly found in household environments. Product samples are placed on nutrient-containing plates and sprayed with a mixture of these fungi. For 28 days, the test plates are kept at a constant temperature of 84.2°F (29°C) and exposed to high humidity, which are excellent conditions for fungal growth. The samples are then examined for fungal growth. If no growth is present, the product is considered to not support mold/mildew/fungal growth.
Products identified with MAPEI's BioBlock logo have been developed in such a way that they do not support mold/mildew/fungi growth after product installation as certified by external laboratories per industry standard ASTM G21: Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. Common cleaning and maintenance practices are still needed.
For homeowners and building owners, the advantage is after installation. MAPEI’s BioBlock products will not support the growth of mold/mildew/fungi – with adequate cleaning and maintenance practices.
The advantage for contractors and installers is that MAPEI’s BioBlock products do not support the growth of mold/mildew/fungi – with adequate cleaning and maintenance. Therefore, their use can prolong the life of an installation, resulting in fewer callbacks for installers and contractors.
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