Cleansing or laundry agents are substances which aid the removal of dirt. They include water, detergents, bleach and soaps.
Water is a very important cleansing agent. It serves as a solvent. The natural sources of water are rain, spring, well, river, lake and sea. Water is used in laundry for the following:
i. Water can be used to cleanse articles with non-greasy dirt to a certain extent;
ii. Hot water will soften and melt grease. However, it requires soap to emulsify and remove the grease;
iii. Water is used for soaking clothes and household articles before washing; and
iv. Water is also used for rinsing. Rinsing is important to remove all the soapy water and dirt and to give the clothes a good colour.
There are two major types of water, i.e. soft and hard. Soft water is got from rain that falls. It passes through the atmosphere, thereby dissolving carbon dioxide. Rain water when collected directly from the atmosphere is known to be the best for washing, because it contains only carbon dioxide, which has no effect on the washing. Soft water does not form scum in water. It brings out lather easily with soap.
Hard water is due to dissolved substances which water collects from the ground. When water is purified, the salts that cause hardness are still in the water. Hard water has no effect on drinking and other uses, but it has on laundry work. It does not form lather readily with soap during laundry work, but scum is formed as a result of insolubility of the soap. If it comes in contact with fabrics, it may result in the softening and discolouration of such fabrics.
Hardness of water is classified into two groups namely:
i. Temporary hardness
ii. Permanent hardness
This is due to the presence of magnesium bicarbonate in the water. Boiling helps to remove hardness from the compound formed with calcium carbonate. On boiling, the insoluble calcium carbonate is precipitated and carbon dioxide is driven off, making the water soft. Hardness in the water cannot be removed by boiling alone; rather, the addition of lime or calcium hydroxide will completely remove this type of hardness. Lime and sodium carbonate can also be used to remove temporary hardness in water.
This is due to the presence of calcium and magnesium salts as sulphate and chlorides. The hardness is removed by a chemical exchange. The calcium sulphate which causes the hardness reacts with sodium carbonates to form calcium carbonate and sodium sulphate. Calcium carbonate is precipitated and carbon dioxide is given off, which has no adverse effect on fabrics.
Water for laundry may contain both temporary and permanent hardness. In this case, borax or ammonia may be used to remove the hardness and soften the water for laundry work.
B. Soap and soapless detergents
Soap is also a laundry agent used with water to remove dirt from fabrics. Soap has been in use for a long time, but soapless detergents is as a result of modern technology.
Soap is manufactured in various ways, but the basic ingredients are the same. It is manufactured from plant or animal fats like palm oil, olive oil, cotton seed oil and alkali in the form of caustic soda and caustic potash. Ingredients required for soap making are:
i. One and half bottles of palm oil.
ii. 125g of Soda.
iii. 3 bottles of water.
i. Heat the palm oil until it is clear.
ii. Leave overnight.
iii. Dissolve the soda in water.
iv. Add the dissolved soda to the oil.
v. Stir well.
vi. Soak the mixture until it thickens.
vii. Mould as required the following day.
The thickening formed in the process of addition of alkali to get the soap in the soap-making process is known as saponification.
Characteristics of good laundry soap
1. The soap must give good lather with water.
2. It must be soluble in water.
3. It must not be too soft to touch, except it is jelly or liquid soap.
4. The fabric washed must not be damaged by the soap.
5. The soap must have a good cleansing power.
Synthetic detergents are made from mineral oil or petroleum products, rather than vegetable oil or animal fats. They are not affected by the hardness of water. They contain ingredients which are not present in soaps. Those ingredients enable synthetic detergents to produce lather quickly. The lather formed does not collapse readily.
Types of detergents
i. Light duty detergent:
They do not contain bleaching agents. They are suitable for washing delicate materials. For example, woolen and baby’s clothes. These dissolve readily in water, for example, lux flakes.
ii. Heavy duty detergents:
They can give mild bleaching action. These detergents produce lather readily and are suitable for washing heavily soiled articles. Examples are Omo, Elephant, Klin and Ariel.
Bleaching is used for the following:
i. to remove certain stains;
ii. to make white cotton and linen articles whiter; and
iii. to sterilise sinks, drains, etc.