Dyeing of Wool with Onion Skin

Last Updated on 27/12/2020

Dyeing of Wool with Onion Skin

Ashish Singh
Dept. of Textile Chemistry
The Technological Institute of Textile and Sciences,
Birla Colony Bhiwani, Haryana-127021, India
Email: ashishsingh1496@gmail.com


Due to the result of stringent environmental standards imposed by many countries in response to toxic and allergic reactions associated with synthetic dyes, alternatively colorants and being tried out.

The consciousness of possible risk during manufacturing of synthetic dyes which use of petroleum based raw materials and the hazardous chemical reaction is also increasing for their synthesis; the use of natural dyes have been growing rapidly. Thus, natural dyes, which were not in market some decades ago, are recently gaining importance due to increased consumer interests.

India has a rich biodiversity and a wealth of useful resources and there is no doubt that the plant kingdom can be utilized as a treasure-house of diverse natural colorants.

Several attempts are being made by the scientists throughout the world to isolate natural dyes from different vegetables and flowers. Here, in this paper we have try to isolate natural dyes from upper ( papery) skin of onions and apply them on wool yarn with the help of mordants like alum, copper sulphate and ferrous sulphate. The dyed fabric was subjected for colour measurements and their fastness properties were checked. The results indicate a very strong potential use of such natural resources for dyeing of wool yarn.

Keywords: Extraction, Onion upper skins, Dyeing, Wool, Mordant.

1. Introduction
Nowadays there is a global interest in the use of eco-friendly and biodegradable materials. A considerable research work has been undertaken around the world on application of natural dyes on textile materials. Natural dyes have been used since ancient times. licationpplication of natural dyes on textile materials, natural mes. Use of natural dyes in colouration of textile materials and other purposes is just one of the consequences of increased environmental awareness. Natural dyes exhibit better biodegradability and generally have better compatibility with the environment and possess lower toxicity and allergic reactions than synthetic dyes.

Natural dyes have a wide range of shades and can be obtained from various parts of plants including roots, leaves, flowers and fruits. The natural dyes present in plant and animal are pigment molecules, which impart colour to the materials. These molecules containing aromatic ring structure couples with a side chain are usually requires for resonance and thus impart colour. There is a correlation of chemical structure with colour, chromogen-chromophore with auxochrome.

Wool dyeing with Onion Skin
Fig: Wool dyeing with Onion Skin

Natural dyes are mostly non-substantive and must be applied on the textile material with the help of mordants, usually a metallic salt, having affinity for both colouring matter and substrate. Some of the important mordants are alum, potassium dichromate, ferrous sulphate, copper sulphate, zinc sulphate, tannin and tannin acid. The mordant helps in absorption and fixation of natural dyes and also prevents bleeding and fading of colours i.e., improves the fastness properties of the dyes fabrics. This complex may be formed by first applying the mordant on the textile substrate and then dyeing (pre-mordanting process) or by simultaneous application of the dye and the mordant (meta-mordanting process) or by after treatment of the dyed material with the mordant (post-mordanting).

Nowadays the manufacturing of synthetic dyes involves many carcinogenic chemicals and the effluents, which are discharged in the river or emitted into the atmosphere. This results in ecological imbalance, polluting problems and disturbed environment due to the ample usage of hazardous chemicals and particularly synthetic dyes. Present work was aimed to isolate natural dyes from upper (papery) skin of onions and apply them on wool yarn with the help of mordants. A study was conducted to assess colourfastness of dyed samples.

2. Materials and Methods

2.1 Material
Dried outer (papery) onion skins were used in powdered form. Substrate was 100% wool. Alum and cream of tartar (assistant) was used as mordant and was of laboratory grade purchased from local market.

2.2. Methods

2.2.1 Preparation of wool for dyeing
Pre-mordanting essential for better absorption of dye and getting good fastness properties.

Step 1: Dissolved the alum + cream of tartar (as an assistant) at different concentration separately in little boiling water.

Step 2: Well wetted 100 gm wool yarn was treated with the mordant solution at 80°Cfor 1 hour (M: L ratio = 1:30)

Step 3: After completion of time, material was allowed to cool in the bath and then taken out.

2.2.2 Extraction of colouring matter
A Stock solution of the dye (50%) was prepared by boiling 50 gm of dry outer(papery) onion skin in 100 ml water for 1 h. The extract was filtered, made to original volume for dyeing.

Dyeing was carried out under acidic condition.

2.2.3 Dyeing process
Weight of wool yarn = 100 gm

M.L.R = 1:30

The mordanted wool was dyed with extracted colouring matter at 80°C for 1h, allowed to cool under the dye bath itself. After cooling, the material was taken out, squeezed, washed with water and dried at room temperature.

3. Testing and Analysis

3.1 Evaluation of colourfastness properties
Various fastness tests for dye extracted from outer skin of onion were carried out. These tests assess how permanent the dye is on the yarn.

3.1.1. Evaluation of wash fastness:
Colourfastness to washing of the dyed wool samples was determined using BIS No IS – 3361-1979 wash fastness method. The wash fastness rating was assessed using grey scale by evaluating the loss of shade.

3.1.2. Evaluation of light fastness
Light fastness was determined by keeping samples in daylight, method is based on BIS No IS – 2454-1985. The samples were exposed to daylight for 4 hr, the fading of each sample were determined by using blue wool scale.

4. Results and Discussion
The wool yarns were dyed with chemical and natural colouring matter. It was observed that the dye uptake was good in pre-mordanting method. Fastness properties of dye extracted from onion skin are tabulated in table 4.1

Table 4.1 Colourfastness properties of wool yarn dyed with extract of dry outer onion skin using different concentration of alum.

Concentration of mordantWashing fastnessLight fastness
 100% CW2Poor2Poor

The dye extract was found suitable for wool yarns. Various shades were obtained from the pre-mordanted wool yarn with alum at different concentration.

The evaluation of color fastness to wash and light using alum as mordant is presented in table 4.1. At 3% concentration of alum, washing fastness and light fastness was good. At 6%, concentration of alum washing fastness and light fastness is same as that of 3% concentration of alum. At 9 %, concentration of alum washing fastness was fair whereas light fastness was good.

5. Conclusion
A global awareness is already in place favouring the use of natural resources for protecting the environment and earth from pollution and ecological imbalances. Hence, the present scenario is directed towards the utilization of natural dyes. In present research work, it was found that wool could be dyed with dry outer (papery) onion skin. Various shades can be obtained using chemical and mordant. The parameters like concentration of dye, temperature and timing are also optimized for better results. With regard to colorfastness, the tested samples exhibit good fastness to washing and light.


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