Porcelain as a material has various applications, but for ceramic tile, it maintains an exalted status. The terms “ceramic” and “porcelain” often are used interchangeably, but some consider the two different. However, porcelain tile is, in fact, a variant of ceramic tile, and it possesses unique attributes.
While the word “ceramic” derives from a Greek word meaning “pottery,” something acquired from its common ancient application, the etymological roots of “porcelain” arose in Thirteenth Century Italian, directly from Italian porcellana. This literally means “cowrie shell.” As such, porcelain is white, translucent, strong, and dense, a collection of attributes making it ideal for fine china.
However, according to the ceramic tile industry, there is a far more specific definition of porcelain. Porcelain tile is, according to ANSI A137.1:2022 – American National Standards Specifications for Ceramic Tile, a ceramic tile that has “a water absorption of 0.5% or less.” It is made generally by the pressed or extruded method.
This minimal level of absorption is measurable in accordance with the test method addressed in ASTM C373-18: Standard Test Methods for Determination of Water Absorption and Associated Properties by Vacuum Method for Pressed Ceramic Tiles and Glass Tiles and Boil Method for Extruded Ceramic Tiles and Non-tile Fired Ceramic Whiteware Products.
This international standard covers procedures for determining water absorption, bulk density, apparent porosity, and apparent specific gravity of non-tile fired unglazed ceramic whiteware products, glazed or unglazed ceramic tiles, and glass tiles.
The definition of porcelain tile is clear and austere, but misunderstandings on the definition of porcelain tile, as well as issues with mislabeling, have persisted over the years. These incidents have resulted in complex and costly problems. In response, the Ceramic Tile Distributors Association (CTDA) and the Tile Council of North America (TCNA), an ANSI-accredited standards developing organization and publisher of ANSI A137.1:2022, jointly established the Porcelain Tile Certification Agency (PTCA).
The PTCA elevates the eminence of ANSI A137.1:2022 and ASTM C373-18, offering a certification program for manufacturers and sellers of porcelain tile. This program is predicated on strict compliance of conforming porcelain tile when tested in accordance with ASTM C373-18. Products marked with the PTCA Certification Mark are guaranteed to be porcelain tile.
My contractor installed porcelain tile that was stored outside and accumulated mold spores. The tile had a moldy odor, but after installation it went away, however now the tile has gray spots that do not wash off. It appear that the mold spores that attached itself to the tile found the moisture it needed to grow after it was installed with the wet thinset underneath. The store and the sales rep maintain that because the tile is porcelain this cannot be the case. I think since the tile is not completely moisture resistant, it is possible that the mold can grow up from the back and thus appear on my white tiles. Your thoughts are welcome.