Textiles are often dyed, with fabrics available in almost every colour. The dyeing process often requires several dozen gallons of water for each pound of clothing. Coloured designs in textiles can be created by weaving together fibres of different colours, adding coloured stitches to finished fabric, creating patterns by resist dyeing methods, tying off areas of cloth and dyeing the rest , or drawing wax designs on cloth and dyeing in between them , or using various printing processes on finished fabric. Woodblock printing, still used in India and elsewhere today, is the oldest of these dating back to at least 220 CE in China. Textiles are also sometimes bleached, making the textile pale or white.
Textiles are sometimes finished by chemical processes to change their characteristics. In the 19th century and early 20th century starching was commonly used to make clothing more resistant to stains and wrinkles.
Eisengarn, meaning "iron yarn" in English, is a light-reflecting, strong material invented in Germany in the 19th century. It is made by soaking cotton threads in a starch and paraffin wax solution. The threads are then stretched and polished by steel rollers and brushes. The end result of the process is a lustrous, tear-resistant yarn which is extremely hardwearing.
Since the 1990s, with advances in technologies such as permanent press process, finishing agents have been used to strengthen fabrics and make them wrinkle free. More recently, nanomaterials research has led to additional advancements, with companies such as Nano-Tex and NanoHorizons developing permanent treatments based on metallic nanoparticles for making textiles more resistant to things such as water, stains, wrinkles, and pathogens such as bacteria and fungi.
Textiles receive a range of treatments before they reach the end-user. From formaldehyde finishes to biocidic finishes and from flame retardants to dyeing of many types of fabric, the possibilities are almost endless. However, many of these finishes may also have detrimental effects on the end user. A number of disperse, acid and reactive dyes have been shown to be allergenic to sensitive individuals. Further to this, specific dyes within this group have also been shown to induce purpuric contact dermatitis.
Although formaldehyde levels in clothing are unlikely to be at levels high enough to cause an allergic reaction, due to the presence of such a chemical, quality control and testing are of utmost importance. Flame retardants are also of concern where the environment, and their potential toxicity, are concerned.Testing for these additives is possible at a number of commercial laboratories, it is also possible to have textiles tested for according to the Oeko-texcertification standard which contains limits levels for the use of certain chemicals in textiles products.