Saturday, September 8, 2012

Natural Dyes - An Age Old Process Goes Back to Eco-Friendly Roots

Around since ancient times, the process of dyeing textiles has strayed from the natural to environmentally damaging. Pigments from crushed plants rubbed into cloth evolved into use of boiled water mixed with crushed fruits, wild berries and plants to distribute color through fabric. This allowed for a broader range and a more steadfast color on the fabric. With the development of high tech fabrics (nylon and polyester) that do not readily absorb the color from dye water baths, came the creation of synthetic dyes using toxic chemical compounds and heavy metals to more readily 'wash' the color into the fabric.

The use of an exorbitant amount of water for fabric dyeing has continued in today's processes. It is estimated about 75 gallons of water are needed per pound of fabric. Dioxins and mordants (mineral salts that create a chemical link to adhere the dye to the fabric) are part of the toxic run off from synthetic dye processes that find way into ground waters causing damage to rivers, lake and oceans. Approximately 1/5 of industrial pollution stems from textile dyeing. Another key factor in the dyeing process is temperature. Large amounts of energy are used to heat the dyes. Many synthetic dyes are highly toxic to workers, and may cause adverse health effects to those who wear dyed clothes. Problems caused range from skin rashes, headaches and muscle pain to breathing difficulties and even seizures.

Dye Types 
The two major types of dyes are natural and synthetic. The natural dyes are pigments extracted from natural substances such as plants, animals, or minerals. Synthetic dyes are chemicals synthesized in a laboratory some of which contain metals.

Synthetic Dyes 
Synthetic dyes fit into different classifications as follows;

Basic - are water-soluble and are used with a mordant. They are not color fast and are generally used for treating fabrics that have already been dyed with acid dyes.

Direct - adhere without mordants. They are not very bright and have poor colorfastness.

Mordant or Chrome - are acidic in character. To get the needed bonding actions, sodium or potassium bichromate is added to the dye bath.

Vat - are insoluble in water and cannot dye fibers directly but need an alkaline solution for them to adhere to the textile fibers.

Reactive - react with fiber molecules to form a chemical compound. They are applied with an alkaline solution and sometimes heat treatment is used for creating color shades.

Disperse - are water insoluble. These dyes are ground into a paste or powder that gets dispersed in water dissolving in the fabric fibers.

Sulfur - are insoluble and made soluble by the help of caustic soda and sodium sulfide. Dyeing is done at high temperature with large quantities of salt so that the color penetrates into the fiber.

Pigment - need resins and high heat to adhere to the fabric.
The most dangerous and damaging to humans and the environment are Azo Dyes. The largest group of synthetic dyes, they are manufactured using a crude oil base. When put in contact with saliva or perspiration they can release aromatic amines that cause a health concern as they are carcinogenic and easily absorbed into the body.

The least eco damaging of the synthetic dyes are the Low-Impact Fiber-Reactive. These chemically adhere to the fibers of the fabric creating a strong bond hence less dye is wasted in water runoff. Being an expensive dye to use, it is also better to reclaim the dye from the used water rather than discard it. Lower temperatures needed to apply these dyes make them less energy intensive than azo dyes. Low-impact dyes typically do not contain heavy metals or toxins but are still synthetically made from petrochemicals. Not affected by saliva or perspiration they are safer to use than azo dyes but still should be avoided by the chemically sensitive. Because of the wide range of colors that can be created, eco aware clothing companies choose low-impact fiber-reactive dyes to remain environmentally conscience.

Natural Dyes 
Natural Dyes consist of colors extracted from plants, earth clays and insects resulting in less harm to the ecosystem. Although they still require metallic salts- aluminum, iron, chromium, and copper- to ensure the color stays on the fabric these benign salts are environmentally friendly.

Most natural dyes are Vegetable Dyes made from plant sources - roots, berries, bark, leaves and wood. The mordants required to adhere them to fabric are again benign salts. Vegetable dyes take a large quantity of dye to thoroughly color fabric and the impact to the environment is dependent on the raw materials used. If the raw materials came from areas heavily fertilized, the impact to the environment is greater. The key is to find natural sources or organically farmed sources which eliminate the negative environmental impact.

One of the most eco-friendly dye ingredients is Clay or Dirt. Clay and Dirt Dyes use minerals and irons from the earth avoiding the use of synthetic ingredients. Sources can easily be found that yield a consistent color. Beautiful colors can be achieved by blending different clays and adding pigments available in nature. Modern developments have improved the colorfastness of this form of dye. The process does not need any form of salt, only natural or biodegradable materials are used to improve the clay's natural dyeing abilities. There is no negative environmental impact including harm to waterways.

Make an Eco-friendly Dye Choice 
The purest eco-friendly choice of color textiles is to choose those made from color-grown cotton or natural color wool from sheep and alpaca. But for those of us who like pizazz to our fabrics there are healthier and more eco-friendly alternatives when it comes to dyeing textiles. To avoid environmental damage from toxic waste water runoff and possible health issues steer clear of fabrics using synthetic dyes especially those using azo dyes.

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