One of cotton’s great qualities is that as a natural fibre, it dyes very well. Centuries ago, cotton was dyed with natural dyes such as indigo, cochineal and ochre. Today, chemical dyes are used to secure the consistency and durability of the colour. Here is a look at the various processes.
In this process, the yarn gets dyed before it is woven. The thread is wound around cylindrical packages that are perforated and put on vertical spindles that go in a cylindrical machine to be dyed. This is called package dyeing. It involves dye being forced in and out under pressure through the packages to ensure even coverage. Now the thread can be woven to produce various effects such gingham, checks, plaids, stripes and various other effects. Cotton dyeing comes under great scrutiny for its huge water consumption, and research is being carried out to find less ecologically harmful methods.
Piece dying is generally used to achieve one solid colour. It’s a basic method in which a length of fabric is prepared for dyeing. It then goes full width through a solution of hot dye before passing through padded rollers that evenly distribute the colour before removing the excess liquid. There are many variations on this method. In places like India, you might still find families that will twist the length of cotton fabric into a rope and pass it through vats of dye in their backyard. On the other end of the spectrum, you will see completely mechanised factories that dye thousands of yards daily.
With automatic screen bed printing, intricate, hand-crafted effects can be achieved like those that can be seen on cotton prints at places like https://www.higgsandhiggs.com/fabrics/plain-cotton-fabric.html. Designs are produced on individual screens of flat mesh that block out the negative spaces of each colour. Screen printing can also be done on a rotary machine.
Printing generally gets done on finished lengths that have been prepared for printing. Similar to printing on paper, different colours can be applied in one operation performed by a roller machine. Various copper rollers are used depending on the design and colours needed. With a very well synchronised machine, the fabric is rolled between the different coloured rollers and a rotating drum to pick up colour from the engraved part of the roller. Drying and heat setting follow immediately.