Tech Note:
Procedure of grading
From Appendix Section 10, American National
Standard Institute (ANSI) for Ceramic tile installation.
APPLICABLE INSPECTION PROCEDURE
Procedure for Determining Structural Defects in Flat Tile and Trim Units Flat Tile
Stack 8 pieces of flat tile face to back. Turn the stack with
one edge up on a table and straighten the stack so that no tile protrudes vertically
or horizontally from the stack. Standing next to the table so that the eyes are
approximately 2 feet from the tile, inspect the edges of the stack which are up,
for cracks running in the direction of the length or thickness of the edges. Remove
any tile which shows one or more of such defects. Turn the stack 90", repeat the
inspection and continue turning the stack until all four edges have been inspected
in this manner. Cracks emanating from the back and progressing in the direction
of the face shall not be considered defects if they do not exceed in length, one-third
of the thickness of the tile.
Chips on the back of the tile shall not be considered defects unless they extend
to the face of the tile.
Procedure for Inspecting Ceramic Tile for Facial Defects
Board Size
36" high x 48" long.
Inspection Board Support
Angled board with top edge of tile array not above the level of the inspector's
eyes.
The Array
Two arrays of 40 pieces of 6"x 6" tiles arranged in 8 vertical columns, 5 tiles
high.
Light Source
Light source shall be in position one foot behind and one foot above the inspector.
Inspector's Position
Draw a line l/4 inch wide on the floor at a distance of 36 inches from a vertical
plane through the bottom edge of the inspection board. Inspector is to stand erect
without leaning and having his feet positioned behind the line, but as close to
the line as practical, and centered left to right in front of this board while viewing
the tile array.
Viewing Time
60 seconds per tile array, or 6 seconds per square foot of tile array.
The Array
Two arrays of 20 pieces 12 x 12 tiles arranged in 4 vertical columns, 5 tiles high.