3. How may the two be distinguished?
Experiment 25—Test to Distinguish Dyed from Printed Fabrics
Apparatus: Knife-blade.
Materials: Cotton fabrics.
Reference: Textiles, page [65].
Printed fabrics may be distinguished from dyed by observing the back side of the cloth, and noting whether or not the pattern on the face of the cloth penetrates through to the back, or only the outline shows. In case the figure or pattern is on both sides of the fabric, it may be distinguished from the dyed by taking one thread of the suspected sample, and by the means of a knife-blade attempting to scrape off the coloring on the surface of the thread. If the dyestuff has penetrated into the interior of the thread, it is not printed.
Generally speaking, printed fabrics are known from dyed fabrics by the fact that the former have the design printed on the face of the cloth. This is called direct printing. The best dyed fabrics are obtained by dyeing in what is called a jig, and the whole fabric is saturated with color. Most, if not all the cloths which you see in the retail dry goods stores which are in plain colors are dyed in the jig. Some of the cheaper qualities of dyed fabrics are padded in a mangle, but there has been a very small quantity of these goods on the market for many years.
Printed fabrics may be made as fast as dyed fabrics; it all depends upon the process by which the goods are converted. Within the past few years great headway has been made in dyeing with what are termed vat colors. Indanthrene is a vat color and a great many mills have used this class of dye successfully in dyeing plain shades. This is what would be termed a fast color in every sense of the word. There are a number of dyestuff makers in Europe who put vat colors on the market, but they all call them by different names. Vat colors have been used with success in printing during the past year or two, especially on shirting fabrics, and these colors are fast to both light and washing. Most direct colors used for printing or dyeing are equally fast to light and washing, but of course they will not stand the test as well as the vat colors mentioned above.
The essential qualities of a good printed fabric are its ability to withstand exposure to light and washing. In printing, of course, a greater variety of desirable styles can be obtained than by dyeing, in fact there are certain popular lines of goods now on the market the effect of the designs of which cannot be obtained in any other way than by printing. At the same time, although the field in designing for dyed fabrics is limited, some very handsome effects can be obtained.
It will not be many years before a large proportion of the printed and dyed fabrics put on the market, both foreign and domestic, will be in the vat colors which, as stated above, are very fast. Even at the present time there are many mills that are using this class of colors entirely, especially the mills which manufacture woven fabrics.