Texture Appearance Retention Rating (TARR) - Hexapod Information

EXPLANATION OF TEXTURE APPEARANCE RETENTION RATING

The Texture Appearance Retention Rating (TARR) is one of the accepted wear test method used throughout the world for commercial and residential carpeting. The test evaluates wear properties of a carpet when exposed to a known number of cycles. It is difficult to predict the actual life time of a carpet using simulated tests. To date there is no documented research that quantifies carpet life based on any accelerated wear test. Variables such as installation technique, padding, cleaning and maintenance, and amount of traffic in a concentrated area will influence a carpets’ ability to withstand use. Further, the color of a floor covering can also improve the carpets ability to hide wear patterns. Therefore, TARR results should be used to compare different carpet's simulated wear characteristics for a given application, and not for estimated life of the carpet.

HEXAPOD DRUM TEST

The Hexapod Drum Test is a nationally and internationally recognized test. The American Society for Testing and Materials (ASTM) assigned the test standard number D5252 to the method. The method is summarized below.

TARR	TRAFFIC VOLUME	TRAFFIC CLASSIFICATION
Less than or equal to 2.0	Light	A
2.5	Moderate	B
3.0	Heavy	C
Greater than or equal to 3.5	Severe	D

Carpet is placed into a drum with a studded tumbler. The carpet is subjected to 12,000 revolutions in the drum with a suitable tumbler. After running the test the specimens are compared to a control sample using ASTM D7330 to assess the texture change of all wear tests. The difference between the control and exposed piece are judged versus a set of TARR performance scales. The scales range in intervals from 5 to 1 (in 0.5 step increments). A grade of “5” means that there was no visual difference between the test and control pieces. A grade of “1” means that there was a extreme change in test specimens’ appearance. In commercial settings the following grades are suitable for the listed traffic area.

The grades are determined by a panel of 3 or more judges. Each judge independently grades the carpet for TARR to the nearest 0.5 units. The grades are then compiled and averaged then rounded to the nearest TARR scale. Because the wear grading processes is based on the aesthetic change in appearance of a test specimen, results are subject to human error. ASTM has measured the typical variation of the method to be between labs in the 0.5 grade range. This means that if the same sample were graded by several different labs the difference in results could vary between the labs by approximately 0.5 grading units. This is simply the variation different judges have in perception of a tested carpet's aesthetic characteristics. There are other variables that influence wear results. Some of the more common are:

1. Color: Since carpet is three dimensional, as the surface of the new carpet is trafficked, the surface starts to be compressed and the yarns are frayed. The applied wear disturbs the original properties of the carpet, resulting in a change in the way light is reflected back to the user’s eyes. The viewer’s eye translates the difference in light reflectance as a color difference attributed to wear. Dark colors reflect less light, and therefore, more wear is required to cause our eyes to see changes in the carpet surface versus a light color of the same construction. 
2. Human Error: As discussed earlier, the grades are assigned based on the aesthetic appeal of the carpet to the TARR scale. Statistically, the variation of the judges should not be more than 0.5 grading units between labs. Several actions are put into place to minimize the human grading factor, such as: grading scales, consistent lighting, multiple judges, and averaging of results.