A stain is defined as a discolouration brought about by contact with a foreign substance which is difficult to remove.
Like first-aid in an accident, the treatment of stains requires immediate action. Some of the first-aid treatments include blotting, grease absorbent, salt absorbent and often a cold water rinse.
It is virtually impossible to guarantee stain removal, as the agents that are used to remove the stain often have an adverse effect on the fibre contained in the fabric.
However, a set of general rules for stain removal may serve as a guideline.
- Identify the stain
- Deal with the stain as quickly as possible. Remove excess staining material immediately.
- Test the stain removal agent in an inconspicuous place.
- Avoid hot water with an unknown stain.
- Use simple methods before resorting to the use of chemicals.
- Use milder agents then stronger ones.
- Repeated mild applications are better than one strong one.
- Ensure that the stain removal agent has been neutralized or washed away.
There are two major factors which are responsible for ensuring correct stain removal. One is the stain removal agent and the other is the method of stain removal. It is important to select the right stain removal agent. However, this becomes complex due to the many fibres and fibre blends that are used in the fabric since they may get damaged by the agents used.
Identification of stains
Identification of stains helps in selecting the reagents and procedures to be used for stain removal. Stains can be classified based on:-
- Based on colour– for example, a red stain can be of tomato, lipstick, nail polish, blood etc.
- Based on Texture-by touching surface of stain it can be deduced:- If hard it may be an egg; if soft it may be oil, ghee, lipstick; if sticky can be of glue and gum.
- Based on Smell– every stain has a distinct smell like eggs, medicine, food, perfume
Classification of Stains
BASED ON SOURCE
- Animal stains– such as blood, eggs, milk, meat etc
- Vegetable stains– these are caused by plant products such as tea, coffee, juices, fruit etc
- Grease and oil stains– These stains are from grease or some pigmented matter eg. Butter, oil, paint, tar, grease.
- Mineral stain– These stains are caused by rust, writing ink, medicines.
- Dye stains- Caused by henna, tobacco, chocolate, tea, coffee etc.
- Wax stains– Caused by nail polish, lipstick and shoe polish
- Acidic stains– these include vinegar, perspiration, urine, medicines etc.
BASED ON DEGREE OF ABSORPTION:-
- Absorbed stains– the stains which penetrate the fabric completely like ink, tea, coffee, syrup
- Built up– These stains which leave residue on top of fabric like lipstick, nail polish, chewing gum, chocolate
- Compound– when it is a combination of both of above
STAIN REMOVING AGENTS:-
There are five main stain removing agents: –
- Organic solvents
- Acids
- Alkalis
- Bleaches
- Enzymes
i)Organic solvents – These dissolve grease and require care because they are inflammable and harmful if inhaled. Generally, it does not harm any fibres or dyes. When using, an absorbent cloth should be placed underneath and work from the outside of the stain inwards.
E.g. Flammable-benzene, acetone, amyl acetate, methylated spirit, white spirit,
Non inflammable-Carbon tetrachloride(Ccl4), Perchloroethylene(PERK), trichloroethylene. These take out stains like chewing gum (after scraping), grease, oil paint, lipstick, ballpoint ink, etc.
ii)Acids –Dilute acids can be used on most white fabrics, but most coloured ones get affected. They affect all animal fibres. It is always better to use weak acidic solutions several times than using stronger acidic solution. After treatment, wash using detergent or thorough rinsing should be done. eg. Acetic acid, Citric Acid, Oxalic Acid.
Acids remove metal stains (especially iron moulds, rust and iron stain left by blood).
iii)Alkalis – Alkalis remove old and heavy vegetable stains (tea, coffee, wine, etc.) from white linen or cotton effectively. Animal fibres may be adversely affected by it. E.g. soda, borax.
iv)Bleaches – Bleaching is the process in which a coloured substance is changed into a colourless one. Bleaching weakens fabrics; hence extreme care should be taken.
Oxidizing bleaches liberate oxygen from the stain and render it colourless. Most commonly used is Sodium Hypochlorite. It removes obstinate stains in white cotton and linen but it ‘fixes’ iron stains. Hydrogen Peroxide is slower acting and is used on white fabrics. Sodium perborate is the bleach present in most detergents and safe on most fabrics.
Reducing bleaches remove oxygen from the stain and add hydrogen to the coloured stain rendering it colourless. Sodium hydrosulphite is the most commonly used one. It is used on white clothes for removal of iron stains and stripping dyes.
v)Enzymes – Enzymes like powdered pepsin are used to remove protein stains like egg, perspiration, blood, etc. at a temperature of 40-50 degrees.
Stain Removal Method
According to mode of action:–
a)Solvent action- Here solvent or water is able to dissolve the stain like ballpoint ink stain.
b)Mechanical action:- This dislodges the stain without dissolving it.
c)Chemical action- Chemicals produce an oxidation or reduction reaction which helps to remove the stain.
d)Absorption- Certain powders such as fullers earth are able to absorb the stain like grease and oil.
According to method of application:-
a)Drop method- the stained part of the fabric is stretched and small drops of stain removal agents are poured on it with a dropper.
b)Dip method- The stained area of the fabric is immersed in the stain remover solution. This is the ideal method when stain is large or if there are many spots on the fabric.
c)Steam method- Stains on wool, silk or any coloured fabric can be removed by steaming. The stained area is saturated with steam by spreading the cloth over a basin half filled with hot water into which a small amount of appropriate removal agent has been placed.
d)Sponge method- the stain removal agent is applied on the stained area of the fabric with a sponge. This is the most frequently used method of stain removal.