SETERIE GR②

Quality Control

At the end of processing, quality control is carried out, that is, it is certified that the fabric meets all the necessary requirements and is, in summary, "ready for the needle," meaning ready to be manufactured. It would be good practice to carry out quality control at the end of each production phase, but unfortunately, quality control is often performed only on the finished fabric. In addition to certifying the exact metric dimensions in length and height of the piece, quality control can also perform a series of laboratory tests to certify compliance with customer requirements, market needs, and any specifications present in technical documents. All those verification operations that do not need to be carried out in a laboratory, as they assess defects visible to the naked eye, are performed on a machine called a "specola," which transports the fabric in a condition of absolute absence of tension, so as not to affect dimensional stability (with particular attention to jerseys, tulle, and stretch fabrics), generally making it run at a variable speed that allows the operator sufficient visual perception of any defects. This operation therefore allows the calculation of the fabric's length and height and makes it possible to remedy, where possible, small imperfections (such as knots, double threads, broken threads, small print stains that can be removed by manual touch-up, etc.). Finally, it allows the operator to mark, by means of notations on the selvedge, the presence of defects that cannot be remedied. In such cases, they are recorded with codes through an appropriate computer system, which at the end of the inspection highlights the percentage of defect repetition and the resulting possible unacceptability by the final customer. Even if the fabric falls within acceptable limits, the customer is informed of the percentage of defects present to prevent the cutting phase from being carried out on lengths where they are too frequent. The notations applied to the selvedge can be differentiated by using different colors according to the type of defect.

Test

In addition to visual inspections, sufficient material is taken from the fabric during the inspection phase to be subjected to various laboratory tests and to verify its compliance with the requirements requested by the customer. The main characteristics that are checked are the following: light fastness; water fastness; dry cleaning fastness; sweat fastness; fastness of particular processes (e.g. flock printing, foil applications, etc.); dimensional stability; verification of usable width; verification of weight; verification of head-to-tail; verification of center-to-selvage and selvage-to-selvage. To verify light fastness, the sample is subjected to a specific test that consists of exposing the sample to a light source for a certain period of time, together with a series of 8 samples of the so-called "blue scale." These samples have been dyed with dyes of different fastness, so at the end of the indicated time, our sample is compared with the blue scale tabs and, based on which one has undergone the same degree of dye degradation, the fastness grade is determined. The minimum value considered commercially acceptable is value 3.

NUMERICAL VALUE OF THE BLUE SCALE

INTERPRETATION OF LIGHT FASTNESS VALUES

1 very poor fastness

2 poor fastness

3 moderate fastness

4 fairly good fastness

5 good fastness

6 very good fastness

7 excellent fastness

8 exceptional fastness

To verify water fastness, a white sample, called a witness, of the same composition as the sample under examination is sewn to both sides of the sample, and it is then washed in water under certain time and temperature conditions. The presence of the witness is necessary because water fastness takes into account both the degradation of the dye and the staining on the white witnesses. The evaluation of the degradation of the original color is done by comparison with the gray scale, determining the degree of visual contrast between the sample under examination and the scale itself. The result is expressed according to the following table and the minimum value considered commercially acceptable is value 3. Water fastness for staining is done by comparing the contrast between the original white witnesses and those that have undergone the test; again, using the gray scale, the index of fastness to staining is assigned, which, as in the case of degradation, has a minimum value considered commercially acceptable, 3. As for dry cleaning fastness, normally if the water washing fastness values are good, the dry cleaning fastness values are even better. The numerical values are the same as for degradation and staining in water. Finally, we have the evaluation of sweat fastness, which also in this case involves evaluating degradation and staining. If the water fastness values are good, they are generally sufficiently good or just slightly lower also in the case of sweat fastness. It is, of course, essential to indicate whether the fastness refers to acidic or alkaline sweat and, given the subjectivity and variability of sweat conditions, the evaluation of sweat fastness is performed only rarely and only if specifically requested.