The main component of cotton is cellulose. Cellulose is a polymer composite constituted by many condensed glucose units (from 600 up to 3000) that form long chains. The number of glucose units in case of raw cotton is about 3600. Before subjecting the cotton to dyeing or printing it is necessary to clean its natural impurities (cotton scouring) and to whiten it so that it will lose its natural light yellow colour. After that, we can finally move on to the dyeing stage. So far, we have always heard about the classic methods of cotton dyeing: among the main colorants we can distinguish the basic dyes, direct dyes, leuco dyes, sulfur dyes and azoic dyes. However, the research in the fabrics dyeing today has been dealing with some new techniques of cotton dyeing.
Let us have a look at the main ones.
Coloured resins fixed by a laser beam
This technique is based on immersing the cotton in a bath containing a coloured resin. Then, a laser beam engraves the chosen pattern onto the fabric surface. The resin reticulates at the laser application and it gets fixed onto the surface of the fabric.
Finally, the fabric is washed and the non-reticulated resin excess is removed.
Coloured resins tie-dye
The cotton is immersed in a coloured resin bath. During the drying stage, the resin shifts towards those parts of the garment that dry more quickly. There, the resin reticulates.
After that, the garment undergoes the colouring stage again so that the dyes get fixed onto the parts of the surface where the resin is not present (folded parts or stitching, typically).
Coloured resins sprayed onto the surface of the garment
The coloured resin is sprayed onto some parts of the surface of the garment (the surface of the garment on the photo).
The drying stage that follows allows the resin to reticulate and get fixed onto the surface of the fabric contributing to its shiny look.
Dry or wet cleaning?
Here comes the fundamental question: how do we wash this kind of garments?
Can dry-cleaning damage them?
A large part of pigment binders are resistant to both dry and wet cleaning, and to tumble drying as well.
However, if the resin fixing temperature does not cover the established range (150 – 170°C), and if the right catalyst is not applied, the results of the dry-cleaning method might unfortunately, turn out unexpectedly surprising. What is more, in order to improve garments quality to the touch and make the resin more plastic like, some softening or plasticizing additives are likely to be added. These substances are easily removable while dry-cleaning (less easily by wet cleaning), therefore their removal can cause the resins rigidity, and in some cases even cracks formation or resin detachment.
For this reason, it is advisable to apply the wet cleaning method.
Detergo Magazine – October 2016