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Care And Maintenance Of Garments - oxidizing bleaches

Amongst the oxidizing bleaches, the following may be mentioned: 1.Sunlight with moisture, air and grass 2.Sodium Hypochlorite 3.Sodium perborate 4.Hydrogen peroxide 5.Potassium permanganate. Sunlight with Moisture, Air and Grass,Sodium Hypochlorite or Javelle Water ,Sodium Perborate bleach, Hydrogen Peroxide,Potassium Permanganate Bleach,

Introduction

 

A garment that is properly cared for may be expected to last considerably longer than one that is not cared for adequately. It will look better all through its wear-life.

 

Care includes three elements namely cleaning, refreshing and storage. Cleaning is usually a more technical and more involved process than storage or refreshing. Washing and dry cleaning are two major overall cleaning methods. Washing may be either hand or machine. For either process there are variations in the required water temperature, the nature of the detergent used, the use of bleach, the length of soaking and agitation time, the method of moisture removal and the method and amount of pressing required.

 

BLEACHING

 

Bleaching is a complex process of removing colouring or discoloured matter from fabrics and made white. In laundering, the only object in using bleach is to remove stains, which do not respond to normal washing processes. Bleaching should be carried out carefully on all fabrics. Bleaching agents are chemicals hence the correct rate and intensity of bleaching is essential so as to avoid damage to the fabric.

 

On the basis of mode of action, bleaching agents can be classified into three groups as below.

 

             Oxidizing bleaches

 

             Reducing bleaches

 

             Optical bleaches

 

 Oxidizing bleaches: These have oxygen as a chief component which is liberated and on contact with the stain, forms a colourless compound.

 

 Reducing bleaches: These remove the oxygen from certain kind of stains and so, reduce them to a colourless compound.


Amongst the oxidizing bleaches, the following may be mentioned:

 

            Sunlight with moisture, air and grass

 

            Sodium Hypochlorite

 

            Sodium perborate

 

            Hydrogen peroxide

 

            Potassium permanganate

 

1.a) Sunlight with Moisture, Air and Grass : This is the oldest, easiest, cheapest and perhaps the best method of bleaching cotton and linen, and of removing colouring matter which on contact with oxygen becomes colourless. The oxygen from the air and grass liberated by the sunlight and in conjunction with moisture is the active bleaching agent. The article, particularly the stained part, must be moistened with water and exposed to the sun preferably on grass or shrubs or plants until the colouring matter disappear after which the fabric must be removed immediately. Otherwise long exposure to the sun will weaken it.

 

Before bleaching with any of the oxidizing chemical, the metallic buttons and other similar parts if any, must be removed since their oxidation may cause black stains on the fabric.

 

1.b) Sodium Hypochlorite or Javelle Water : 1lb (480g) washing soda � lb chloride of lime, 1 quart boiling water 2 quarts cold water.

 

Method: Take a solution of washing soda and boiling water. Mix chloride of lime with cold water. Stand the mixture for sometime, so as to settle down. Decant the clear liquid and add it to the washing soda solution. This will give sodium hypochlorite and calcium carbonate which will precipitate. Allow the precipitate to settle and then strain off the clean liquid. This must be always stored in coloured bottles as it deteriorates in the light.

Use: Sodium hypochlorite is a strong bleaching agent and can be used on white cotton and linen. Dilute it with equal quantity of hot water and sponge the strained portion with it until the stain is removed. Rinse the fabric in the plain water to wash out any residual amount of bleach.

 

1.c) Sodium Perborate bleach : It is made by mixing solution of borax and caustic soda with hydrogen peroxide. When mixed with warm water, it gives off oxygen and also forms an alkaline solution of hydrogen peroxide, and is used in the preparation of soap powders.

 

Method: Dissolve one ounce (about 28g) of chemical in one gallon (about 4 litres) of water. For treating animal fibres, neutralize the solution with acetic acid and for bleaching action makes it slightly alkaline with ammonia.

 

Use: Make a solution of sodium perborate in the proportion of one tea spoon to 1 pint of boiling water. Sponge the stain with this solution, mostly used on white linen and cotton.

 

1.d) Hydrogen Peroxide : It is used as an antiseptic and a deodorant. It is a mild and useful agent. It must however be used with great care as it may cause serious injury to fabrics. The compound is available in the market as solution of different concentrations. The chemical is very unstable in air. Hence, to maintain the strength for longer, it must be stored in dark air tight bottles at low temperature. This bleach readily splits up into water and oxygen and so colouring matter is oxidized in its presence. This action takes place most rapidly with alkaline solution.

 

Use: It is a safe bleach on all fabrics and is used for whitening of wool and silk in addition to cotton and linen, which show yellowness due to repeated washings. It must never be allowed to dry in the fabric. The 10 volume strength can be used without dilution for white linen and cottons but for other fabrics, it should be diluted by adding six parts of cold water to one part of hydrogen peroxide. Little ammonia is then added to make the solution alkaline.

 

1.e) Potassium Permanganate Bleach : This bleach has a high content of oxygen which will combine with, so remove, certain obstinate stains. Eg., perspiration, marking ink and mildew. It can be used on animal as well as vegetable fabrics. A brown colour is left in the fabrics which can be removed by treating it with hydrogen peroxide or oxalic acid. Potassium permanganate is available in the form of crystals and can be easily stored in a bottle.

 

Method & Use: Make a solution of potassium permanganate in the proportion of one ounce (about 28g) of bleach with one gallon (about 4 litres) of water for cotton and linen fabrics. For animal fabrics the above solution is diluted 2 fold with water. The fabric is steeped in the bleach for few minutes, and then the excess bleach is rinsed out of fabric which has now stained with characteristic brown colour. The article is then dipped in one of the following solution until the brown stain due to bleach is removed.

 

       Sodium hydrosulphite

 

       Oxalic acid solution (28g in 4 litres of water) or

 

       2% hydrogen peroxide acidified with acetic acid (1 teaspoonful of vinegar for 500ml of bleach)

 

The fabric must be rinsed thoroughly in water after treatment with above chemical.

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