Annex A of technical standard NBR 13818 describes how the visual analysis of the product’s surface appearance should be done. The observer must stand at a distance of 1 meter from the panel formed with the pieces to be evaluated, and examine with the naked eye the existence of defects, such as depressions, stains, spots, protrusions, scratches and cracks, etc.

 

The intentional effects on the surface of the tiles should not be considered a defect, such as, for example, purposeful spots and crackles, color movements. The evaluated parts cannot contain more than 5% of noticeable defects.