CHAPTER FIVE: COLOUR IN FABRIC DESIGN

5.1 Dyeing in Coloured Yarn The term package dyeing usually denotes for dyeing of yarn that has been wound on perforated cores. This helps in forcing the dye liquor through the package. With the start of dyeing cycle, the dye liquor goes on circulating throughout the vessel and tank. This happens till all the dye is used up or fully exhausted. The dye flows through to the yarn package with the help of the deliberate perforations in the tube package. Once full exhaustion is brought about, the carrier of colored yarn is consequently removed from the vessel. A large centrifuge removes excess water from the packages. Finally the yarn is dried using red drying oven.

5.2 Types of Package Dyeing Machines Types of Package Dyeing Machines: 1. Vertical Spindle Machines Vertical spindle machines are common today. The packages are press packed onto the vertical carrier spindles so as to increase the payload. It also aids in the dye liquor circulation and minimising the liquor to fibre ratio. Machineries of this sort can operate at liquor ratios as low as 6:1. The following Figure shows a typical package dyeing machine where the yarn packages are held on multiple spindles. An overhead crane system makes yarn carrier to be entered and removed from the machine room.

2.Horizontal Spindle Machines a. This is an alternative configuration for the vertical spindle machine. b. Dyeing kier is mounted horizontally and the yarn carrier is introduced from a trolley. c. This arrangement effectively replaces the need for crane. d. Horizontal Spindle Machines has simplified the design of the dyehouse building. 3. Tube Type Machines a.Tube type machines have a series of vertical or horizontal tubes into which package carriers get inserted. b.The tubes that form the individual dyeing vessels are linked by common circulation pumps and pipe work. c.These type of machines offers the advantage of flexibility than the above mentioned types. d.This is because individual tubes can easily be blanked off to change the overall load limit of the machine.

5.3 Designing Coloured Fabric Modern looms make possible to design coloured fabric using coloured warp and weft yarns. Various coloured patterns can be obtained in fabric by combining coloured yarns and weave. The process starting from selection of suitable weaves and yarns of different colours. Process conditions of weaving should be taken into consideration. The preparation for coloured warp yarn using weaver’s beam can be prepared in sectional warping by rearranging the coloured bobbins on the creel.

In sectional warping, additional devices are used compared to direct warping: warping table moveable sectional warping beam The process are the same with direct warping only it’s wind section by section using sectional warping beam until it’s complete. The complete sectional warping beam is transferred to the weaver’s beam or to the sizing beam. The colored weft yarns require multi-shuttle looms or shuttles loom equipped with weft patterning devices. The repeat of weave is also importance to determine the number of heald shafts to be used on the loom. The reason is to get a large coloured pattern with a minimum number of heald shafts. The repeat of coloured pattern equals the least common multiple of the weave repeat and the repeat of coloured threads. If these numbers are prime, the repeat of pattern equals their product.

5.3 The Usage of Coloured Yarn in Coloured Fabric Construction of Patterns from A Given Weave and Colour Repeats Example 1, 4 shaft sateen / crepe weave (R = 4). Warp and weft colour repeats are equal to 3; 2 red and 1 white warp threads 1 red and 2 white weft threads. The least common multiple of 3 and 4 is 12. Therefore, the colour pattern repeat is 12 X 12 to produce a fabric on 4 shafts.

Example 2, The weave is same but the colour repeats of warp and weft threads have been changed. The sequence of warp threads is 1 red and 2 white thread. The sequence for weft threads are 2 red and 1 white threads. Such a change gives a new colour but the same size of 12 X 12

Example 3, Honey comb weave with the repeat of 8. Weft overlaps are marked by dots. Colour repeat of threads is as large as 24. The least common multiple of 8 and 24 is 24. The colour pattern constructed is 24 X 24. Weft colour repeat; 8 white threads, 8 red thread. Warp colour repeat; 8 white threads, 8 red thread.

5.3.2 Selection of Weaves for a Colour Pattern Begin by obtaining a colour pattern, depends on the colour repeats of warp and weft threads. Example: Take 8 warp and 8 weft threads. The odd threads are red and the even threads are white. Colour repeat is 2 for warp and 2 for weft. The arrangement of coloured warp threads is shown in the lower horizontal space, and weft threads in the left vertical space. Find the colour of all 64 squares, the intersections of warp and weft threads. The first square is the intersections of red warp 1 and red weft 1. The point of intersection of white warp 2 and red weft 1 can be red or white, depending on the type of overlap (any colour in this square). This square is marked by a dot. The intersection of warp 2 and weft 2 can be white only, because both threads are white. All 64 squares can be divided into 3 groups: red, white and square marked by dots. There are 33 squares marked by dots. Each of these squares can be painted red or white depends on the designer. Many different colour patterns can be created.

If all the squares with dots are white, the first pattern is created:

By painting in red squares, positioned between red squares in vertical direction, red vertical stripes are obtain:

The red horizontal stripes appear on the fabric, while red squares are added in a similar way in horizontal direction:

By painting the dotted squares along the diagonal, zig-zag stripes running appears either from right to left or from left to right:

The dotted squares can be pointed in another manner, so that we get a pattern with closed contours: