Bleached Vs Unbleached Fabrics

Bleached Vs Unbleached Fabrics

Our customers often ask us why the fabrics at Offset Warehouse are mostly off-white or cream, instead of stark white. This confusion stems from the general misunderstanding that natural fibres are pure white – which they aren’t, they are usually cream or nude.

Many of our sustainable fabrics are in their natural and unbleached state, and so therefore are cream in colour. The pristine white colour, often associated with fabric is in fact very unnatural, and the result of bleaching and several other chemical processes.

Join me as l explore more about the differences between bleached and unbleached fabrics in this article, and you will soon understand why pure white fabrics aren’t necessarily pure or eco-friendly.

What Is Industrial Bleaching and Why Is It Done?

natural fibres

To understand why bleached fabrics aren’t that sustainable, we should first look at why bleaching is done in the first place and what happens during the process.

Ready, Set, Dye!

When we derive a fibre from it’s source, it is in its natural form called “greige.” The greige has natural colour and contains impurities. These impurities include pesticides and fertilizers, and in the case of animal fibres, natural secretions and oils. The presence of these impurities and natural colours in the fibre makes it difficult to dye. Hence manufacturers remove this colour, before they start working with it.

How Impurities Are Removed

Scouring and bleaching are the two processes that remove the natural impurities and strip the fibre of its original colour. Let us look at what happens during each stage:

  1. Scouring removes the natural impurities, oils and protective pectin layers that are present in the fibre by dissolving it in suitable wetting agents.
  2. While scouring was traditionally carried out using harsh chemicals, recent technological developments allow textile manufacturers to use bio-scouring and enzyme scouring techniques for similar results, but with lesser environmental impact. We can learn more about this cost-effective and eco-friendly process in this article on Bio-Scouring.
  3. After scouring, the greige is bleached to get rid of colour and to prepare it for dyeing. Bleaching involves excessive use of chemicals, water and energy and results in huge quantities of non-biodegradable waste.  Here’s a look at this process in closer detail.

The Process of Bleaching

Bleaching1

Bleaching agents are substances that remove natural colourants from fibres. These may be oxidative or reductive in nature. The type of bleach used depends on the material and nature of the pigments it contains:

  • Oxidative bleaches like hydrogen peroxide break the chemical bonds in the colour pigments and change its chemical nature so it doesn’t absorb light.
  • On the other hand, reductive bleaches convert double bonds in the colour to single bonds, thus preventing the absorption of light. Sulphur dioxide and sodium bisulphite are reductive bleaches.

The fibre may be bleached at various stages of the processing. It is either done by machines or through hand processing. There are three main stages in bleaching:

  1. First, we treat the fibres with a demineralisation agent that removes the residual oils from the scouring stage.
  2. Next, bleaching chemicals are applied to the fabric for a set period of time to remove all the colours from it.
  3. This is followed by bleach clean-up, where the bleaching agents are washed off and the fabric is rinsed thoroughly.

An elaborate description of the bleach clean-up process is available in this article at fibre2fashion.

Pros and Cons of Bleaching

250-C-NDEBasket3

Beige Basket Weave Cotton

After bleaching, a fabric has a uniform degree of whiteness and it becomes more absorptive. This is why bleaching a fabric will inherently make it better suited for dyeing. Apart from this factor, there is obviously a huge demand for white fabric! So bleaching is commonly used to achieve this whiteness quickly and easily.

However, there are severe environmental and health issues associated with industrial bleaching. We have already seen that it is a chemical process, and the process requires huge quantities of water and energy. It depletes the existing water reserves and the chemicals used pollute water, air and soil – particularly when not disposed of properly.

Chlorine, which is a by-product of bleaching, is a toxic chemical that ends up in our water bodies and soil. This potent chemical will remain in the environment for several years, harming wildlife and leading to respiratory problems and other health concerns in humans.

When we use a bleached fabric, traces of chemicals from the bleaching stage come in contact with our skin. These are absorbed by the body and cause skin irritation and allergies. These harsh chemicals reduce the natural strength of the fibres, making them weak and more prone to damage. Many people don’t believe that chemical residues are possible on fabrics – here’s an article that says otherwise… prepare to be shocked!

Bleaching is sometimes unavoidable in fabric production, but reducing the amount of fabrics that are bleached is always going to be a good thing.

New Technologies That Overcome the Disadvantages of Bleaching

The huge impact of harmful chemicals on our environment has prompted the textile industry to turn to sustainable, bio-solutions instead. DuPont Prima Green is one such revolutionary innovation in bleaching. It uses enzymes in place of harsh chemicals to remove colours from natural fibres. The process also uses less water and energy, and so is environmentally preferable. You can find out more information on this technology at the DuPont website.

As I come to the end of our discussion here, you now know that pure fabric in its original form is not white, but off-white. Unbleached fabric may not be flawless, but it is natural and more importantly, safer for us and our environment. 

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