Who has seen how sheep naturally live, probably understands that you can’t train sheep to stay clean as a poodle and sheep do not wash like kittens. Industry processes wool in huge quantities and uses technological advances for that. They wash wool with harsh and efficient detergents. Here machines as human hands work which can’t have a contact with these agents. At the end of the process wool is being rinsed with an additional amount of lanolin that was lost during the washing. After all wool is handed for people to use. But the way it passes damages the wool fiber and loses the major part of the unique features. So the label published loudly “natural wool” does not mean that it is treated naturally.
The most widely used wool processing methods are carbonizing, chlorating, bleaching or processing otherwise in order to obtain/create different wool qualities.
Carbonising is a continuous process which combines scouring to remove the wool grease and a chemical process which removes vegetable matter such as seeds, burs and grass. Carbonising occurs if the greasy wool contains a high percentage of vegetable matter (%VM), typically in excess of 2% to 3%.
Most of the VM contained in wool is cellulosic in nature, which is broken down into carbon, by firstly immersing in a strong solution (6% to 7% weight for volume) of Sulphuric acid (H2SO4) then followed by baking in a dryer set at 95oC to 120oC. After the VM has been turned into carbon the wool is passed through a series of heavy metal fluted rollers which crush the carbonised burs into dust.
The wool is then passed through a de-dusting unit (rotary shaker) where the dust is separated from the wool by mechanical action.
The wool at this stage is acidic due to the action of being immersed in Sulphuric acid. It then neutralizes (pH 7) by passing it into a solution of alkali containing Sodium Carbonate (Na2Co4). Finally, the wool passes through a final bath containing a solution of Hydrogen Peroxide bleach (H2O2) to improve the colour before it is dried.
Small, barbed scales cover the surface of wool fibers. When wool is machine-washed and dried, these scales can become interlocked, causing the wool to felt and shrink. To prevent interlocking, wool is usually dry-cleaned or hand-washed. Machine-washable wool was made possible by pretreating the barbed scales with chlorine, then, applying a thin polymer coating. This makes wool fibers smooth and allows them to slide against each other without interlocking. Millions of pounds of wool are processed each year in this way. Unfortunately, this method results in wastewater with unacceptably high levels of adsorbable organohalogens (AOX) — toxins created when chlorine reacts with available carbon-based compounds. Dioxins, a group of AOX, are one of the most toxic substances known. They can be deadly to humans at levels below one part per trillion. Wastewater from the wool-chlorination process contains such high concentrations of chlorinated chemicals, that most wastewater treatment facilities in the United States do not accept it. Therefore, most chlorinated wool is processed in other countries, then, imported.
Approximately 75% of machine-washable wool is treated by the so-called Chlorine-Hercosett shrinkproofing process. This method, which guarantees the felt-free superwash standard, works on the basis of chlorination and subsequent coating of the fibre material with a polyaminoamide. The process, which uses large amounts of water as well as dangerous substances, leads to significant pollution of wastewater with organic halogen compounds (AOX). For approximately 1 200 t/a of “Superwash” quality wool produced per year, this process consumes the following quantities of environmentally hazardous substances: 150 t sodium hypochlorite; 220 t resin; and 165 t other auxiliaries (sulphuric acid, wetting agent, defoamer, etc.)
Wool exhibits by nature a pronounced yellow color and also on exposure to light, alkali or by microbial degradation. Commercially, wool bleaching is carried out using either an oxidative or a reductive system, or a combined oxidation/reduction process.
Oxidative Bleaching Method is a treatment with hydrogen peroxide. An activator (eg an alkali) is normally added to increase the rate of bleaching. Typically, wool is bleached at pH 8–9 for 1 h at 60◦C with a stabilized solution of hydrogen peroxide (0.75% w/w). It is generally accepted that, under alkaline conditions, the active bleaching species is the perhydroxy anion (OOH− ), the formation of which is encouraged by higher pH.
Reductive Bleaching uses two most popular chemicals for reductive bleaching of wool are stabilized sodium dithionite and thiourea dioxide. Most reductive bleaching of wool is carried out using stabilized dithionite (2–5g/L) at pH 5.5–6 and 45–65◦C for 1 h. Thiourea dioxide is more expensive than sodium dithionite, but is an effective bleach when applied (1–3 g/L) at 80◦C and pH 7 for 1 h. Whiter fabrics are produced when oxidative bleaching is followed by a reductive process — this is often referred to as “full bleaching.”
While “Labos nakties” production is very close to Mother Nature. Not only the wool we use is natural itself but its processing is also. Commercially processed wool is washed using chemicals. We hand-wash wool using natural soap. The chosen method of processing is much heavier but it ensures high-quality and is environment friendly.