Q: What rub colorfastness grade should dyed zipper tape reach?
Rub fastness is tested with a crockmeter: a white cloth is rubbed against the specimen under a defined load for a defined number of cycles, dry and then wet, and the staining of the cloth is graded against the grey scale. The dry and wet results are reported separately, because wet rubbing almost always gives the lower grade, especially on dark shades.
The load, the rubbing finger diameter, the stroke and the number of cycles are fixed by the method, so refer to the standard text. Prepare the specimen flat and taut; a creased or slack tape gives an unrealistically good result. Test the darkest colour in the range, since black, navy and deep red are the shades that fail, and test after the finishing process the tape will actually receive.
Acceptance is commonly 4 or better dry and 3 or better wet for apparel tape, but a garment with a light lining or a white placket should be specified tighter. Record both numbers, name the method, and keep a retained specimen so a later dispute can be compared against the approved standard.