Why these three
Tensile strength, colour fastness, shrinkage and yarn evenness are the properties checked before thread leaves the plant. Three of them cause almost all downstream complaints.
Colour fastness
Fastness is how well the shade survives washing and light. On polyester the dye sits inside the fiber rather than on it, which is why polyester thread generally holds shade well, but the dyeing has to be done properly for that to hold.
Shrinkage
Thread that shrinks more than the fabric puckers the seam after the first wash. This is a matched-pair problem: the thread is only wrong relative to the cloth it joins, which is why a sample on your own fabric matters.
Evenness
Uneven yarn changes tension as it feeds, and changing tension is what produces skipped stitches and irregular seams. Evenness is controlled upstream at carding and drawing, not at the end of the line.
Stated standard
The mill states that its products meet OEKO-TEX Standard 100 class 1 and REACH, and international garment standards. Ask for the current certificate copy with your first order.
