unit iii stain removal

8/12/2019 UNIT III Stain Removal

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Meaning of Laundering

Most of us think that laundering means onlywashing of clothes. But actually it includes properdrying, finishing and storing as well. Therefore, wecan say laundering consists of three main steps:

(i) Washing the fabrics to remove the dirt.

(ii) Finishing the fabrics by use of starch, gum, blue,

etc., followed by ironing and pressing.(iii)Storing the fabric by properly folding it.]

Laundering means removing dirt

from clothes by washing and thenfinishing them (i.e, starching, ironing)thereby giving them a neat and cleanappearance.


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Importance of Laundering

Why do we launder clothes? Well, we all know

that when we wear clothes they become dirty due tothe dirt, grease, perspiration etc.

The dry dirt can be easily shaken off the clothes,but greasy dirt requires a special treatment calledlaundering.

If dirt is left on clothes:

(i) It is harmful for personal hygiene

(ii) The clothes do not look neat or fresh

(iii) It leaves a permanent mark called stain

(iv) It affects the strength of the fabric.


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STAIN

A stain is a discoloration that can be clearly

distinguished from the surface, material, or medium itis found upon.

Stains are caused by the chemical or physicalinteraction of two dissimilar materials

A stain is an unwanted mark of discolourationon a fabric caused due to contact with anothersubstance, which can not be removed by thenormal washing process and requires special

treatment.


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The basic principle of successful stain removal is not

allowing the stain to become set. Since a fresh stain

dissolves easily, care should be taken to remove it atthe first opportunity.

Different fibers and different types of stains require

different type of stain removing.

Use of incorrect stain removing agent can spoil a

fabric.

Identifying the stain is very helpful in the selection of

appropriate stain removing agent and method.


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IDENTIFICATION OF STAIN

COLOUR

APPEARANCE

ODOUR

TOUCH

STICKINESS


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HOW TO IDENTIFY A STAIN

Stains can be identified by their

Colour:Every stain has a specific colour. For example,

curry/pickle stains are yellow while coffee/tea stains arebrown, grass stain is green, etc.

Smell:

Some stains have a peculiar smell, eg, stains of egg orpaint, by which they can be recognized.

Feel:

Some stains also change the feel of the fabric and can be

recognized on that basis. For example paint makes the fabricstiff to touch whereas Lipstick or shoepolish make the fabricfeel slippery.


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General procedure of stain removal

SOLVENT ACTION

MECHANICAL AND EMULSIFYING

ACTION

CHEMICAL ACTION, OXIDATION ANDREDUCTION

DIGESTION (ENZYME)

ABSORPTION


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NATURE OF STAIN

Acid

Base

Fats and oils

GreaseMineral Oil

Metallic

Metalloid

Natural dyes and pigments in

solution dispersion or

emulsion in aqueous medium

STAINS

Perspiration, urine (fresh), vinegar, medicines

containing nitric acid, picric acid, etc.

Perspiration, urine (old stains).

Butter, cream, margarine, edible oils, machine

oil, hair oil, lard, wax.

Paraffin, vaseline, turpentine, car grease.

Rust, silver nitrate, brass, copper salts, black

ink,chrominum salts, etc.

Iodine tinctures

Herbs, vegetables, flowers, fruit juices, wines,

tea, coffee, cocoa, chocolate, henna, beetle-leaf,

tobacco.


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Synthetic dyes and pigments

in solution dispersion or

emulsion in aqueous

medium.

Sugar solutions and

colouring matter.

Solutions, dispersions or

emulsion in fats or oils


emulsions of dyes orpigments in organic solvents.

Proteinic

Misellaneous

Inks, markers, hair dyes, type-writer

ribbons, water colours, mercurochrome,

gentian violet.

Jams, jellies, syrups, soft drinks,

puddings, etc

Mayonnaise, sauces, ketchup, lipstick,

rouge, mascara, printing ink, polishes,

tar, smoke, soot, crayons.

Oil paints, lacquer, varnish, nail-polish.

Blood, egg. Meat juice, fish slime, milk

Scorch, mildew, certain medicines


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PRINCIPLES OF STAIN REMOVALName of the stain Principal of removal

Acid Neutralization with alkali gives a soluble salt

which can be leached out.

Base Neutralization with acid gives a soluble salt

which can be leached out.

Metal and metal salt Oxidation or Reduction (bleaching) gives a

soluble. colourless salt, removed in washingMetalloid(iodine) Reduction with sodium thio sulphate gives a

colourless. \ soluble salt, removed on washing.

Fats and oils Anyone process

Saponification.

Absorption by an absorbent powderDissolution in a solvent.

Natural dyes and pigments


emulsion in aqueous

medium

Oxidation (Bleaching)


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Name of the stain Principal of removal

Synthetic dyes and pigments


emulsion in aqueous

medium.

One of the following processes

Reduction followed by oxidation.

Oxidation followed by reduction.

Acidification followed by reduction.

Oxidation in acidic medium.

Sugar solutions and

colouring matter.

Solubilization of the sugar and

reduction of the colour.

Proteinic Digestion with enzyme protease.


emulsions of dyes or

pigments in organic solvents.

Emulsification and dissolution in a

solvent.

Mineral oil Anyone process

* Absorption by an absorbant powder.

* Dissolution in a solvent.

* Emulsification.

miscellaneous Special treatment


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CLASSIFICATION OF STAIN REMOVERS

Solvents

Hydrocarbons Benzene, Toluene

Chlorinated

hydrocarbons

Carbon tetrachloride, Trichloroethylene,

Perchloroethylene

Petroleum based Petroleum ether, solvent naphtha, kerosene,turpentine

Alcohols/Ethers/Ketones Ethyl alcohol, amyl alcohol, amyl acetate,acetone, glycerine

Bleaches

Oxidising agents H202, sodium perborate, sodiumhypochlorite, KMnO4 oxalic acid

Reducing agents Sodium hydrosulphite. Sodium thiosulphate,Sodium bisulphite.

Oils/Fats Fatty acids Coconut oil, olein. Oleic acid

Acids

Organic 1% oxalic, 30% fonnic, 1 % acetic whitevinegar. tomato. lime. sour milk. curds.

Inorganic Ammonium hydroxide % , Liquid ammonia10% , Sodium bicarbonate 1

EnzymesProtease, amylase, lipase Enzyme soaps


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Emulsifier

AnionicSoaps, alkylaryl sulphonates. Fatty acid alcohol

sulphonates.

Nonionic

Teepol,

detergents based on: fatty alcohol anda1kylphenol condensates, fatty acid condensates,

fatty amine oxides

Absorbants

Talcum powder,

cornstarch.

French chalk ( 3MgO . 4Si02 . H20 )

Fullers earth ( A1203 . Si02 . X H20 )


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Classification

Acid

Base

Fats and oil

Grease-mineral oil

Metallic

Metalloid

Natural dyes and pigments in solution dispersion or

emulsion in aqueous medium


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Application or Stain Removers

Solvents

Metylated spirit, acetone and dry cleaning solventscan be used successfully on a wide variety of stains,which include blood, various inks and mildew,without causing damage to wool.

Lined garments should be unsewed and worked onsingle layer even if the stain has penetrated at lining.

Place a thick pad of clean, absorb ant white cloth underthe stained material.

The stained side should lie on the pad. Work on thewrong side. With the help of a dropper a few drops ofthe solvent are slowly dropped on the stain.


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Then with cotton wool soaked in the solvent work fromthe border of the stain moving towards the centre.

This will help avoid the halo effect. Move the pad underthe stain and repeat the process several times.

Finally dust some. talc or french chalk on the stain and

allow to dry.

When dry, dust off the chalk and brush. Air out the

garment for the odour to disappear.

When the stain is unknown generally

perchloroethylene is preferred.The solvent is always to be first tested on a little bit of

the fabric.


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Much care is required when using solvents

Most solvents are inflammable, therefore there should

not be any flame in the room (no burner or stove).Even smoking should be avoided.

It is advisable not to switch on any electrical

apparatus while the solvent is being used.

With solvents that emit toxic vapours one has to be

careful not to leave the container open. It is

recommended to wear gloves.

It is best to work in daylight near a window and in awell ventilated room


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Bleaching agents

It is effective in rendering many stains like coffee,indelible pencil and grass colourless. However it

cannot remove metallic stains. In fact if iron or copper stains are bleached the fabric

can be severely damaged.

The following concentrations are used

Oxidizing type:Hydrogen peroxide 1 % solution of 20 volumesconcentration Sodium perborate 1 % solutionPotassium pennanganate 1% solutionSodium hypochlorite 1 % solution

Reducing type:Sodium hydrosulphite 1 % solutionSodium bisulphite 1 % solutionSodium dithionate 5% solution . .


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The stain should be soaked for about 10 minutes in

cold bleach (30C).

In the case of oxidizing bleach, after the stain isdiscoloured it is rinsed in 10% ammonium hydroxide.

When potassium permanganate is used, the stain is

soaked in -1 % solution for 1 minute, followed by

treatment with 1 ero sodium bisulphiteor 1 % oxalic acid.

When sodium hypochlorite is used a few drops of

acetic acid may be added to the last rinse.


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Fatty Acids

These are applied onto the stain and allowed to

remain for one or two hours. The stain is then washedin a synthetic detergent and rinsed thoroughly.

Synthetic Detergents

The stain is soaked in concentrated solution for someminutes and then scrubbed. Finally it is rinsed

thoroughly


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Acids

The following concentrations are

recommended

* Oxalic acid 1 % solution.

* Formic acid about 30% solution.

* Acetic acid - pure commercial product.

The same technique as for solvents is used.

A final rinse in a 1 % sodium bicarbonatesolution or a 10% ammonia solution is given.


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ALKALIES

Washing soda (sodium carbonate), if dissolved in hot

water removes oils and fats.Dissolved in milk and left on the stain for 30 minutes

it will remove sea-water stains from leather shoes and

handbags.

It is used to remove stubborn tea. coffeeand cocoa stains.

Sodium bicarbonate is used at 1 % concentration

while ammonium hydroxide is used as a 10% solutionto neutralize acid stains caused by fruits.

Ammonia removes scorch, fruit. wine and blood

stains.


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ENZYMES:

These are incorporated in certain detergent powders.

When these detergent powders are used the temperatureof the water should be between 30C and 40C.

A soaking period of about 20-30 minutes at least is

required.

Repeated use of enzyme - containing detergent in

washing wool or silk can damage the fabric.

Some people may be allergic to enzyme detergents. It is

advisable to use gloves


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ABSORBANTS

These are dusted on the fresh stain. After they absorbthe oil they are dusted off.

This may be repeated several times until the staindisappears.

Bran from wheat grainwhen mixed with water

gives a sticky colloidal solution which has greatcleaning properties.

Dry branis heated and used as a dry cleaning agentfor furs.

French chalkcan be used on any fabric specially onwhites and pastel shades.


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Fuller's Earthis extremely effective on

carpets, felts and heavy materials, even on

dark shades. It can be easily shaken off.

Magnesium carbonateis an excellent grease

absorbant, It is used for cleaning white wool,

felt or kid.


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