Brief notes on the composition, functions, types and properties of Soaps


Soap is the most widely used cleanser of fabrics. Detergent is anything that will clean, including soap and soap less products. Both remove dirt mainly by a process of ‘wetting out and emulsification. Selection between the two is partly a matter of personal tests and partly dependent on the particular purpose. Soap is more useful for toilet purposes, although a few toilet soaps do consist of a mixture of soap and soap fewer detergents.

Composition of soaps

1. Soap is made from a combination of fatty acids and alkalis. Both animal and vegetable oil fats are used in the manufacture of soap.


2. Naphtha and a little mineral oil, such as paraffin oil may be added to help in its cleansing properties and in the removal of grease.

3. Resin and naphthenic acids (obtained from petroleum) may also be added to improve the effectiveness of soap.

4. The chief alkalis used in soap manufacture are caustic soda and caustic potash,

5. Starch is added to make the soap firm. Generally 2% is a safe quantity to use. In the cold process up to 20% is used.


6. Soap stone or French chalk is often used as a filling agent to the extent of 15 to 20 percent.

7. Salt is used for graining the soap out from a mixture of oils and alkali. The usual proportion is 100 parts of oil to 12 1/2 parts of salt.

8. Water is present in all soaps- the percentage varies with different soaps.

Functions of soap


1. Soap makes the penetration of water into the fabric easier.

2. The soap solution breaks up the grease and dust into small particles present in the fabric, which ultimately comes off the fabric and float in the solution.

3. When soap comes in contact with water, alkali is liberated by the action of water on soap and helps the emulsification of greasy dirt, thus facilitating the washing process.

4. Soap in water increases the pedesis and thus, quickens the removal of non-greasy dirt.


Types of soap Available for Laundry Work

There are different types of soaps available today for the purpose of laundry work. The most commonly used soaps are as follows:

1. Bar soap:

Bar soap is generally used for rubbing on fabrics, available in the form of square blocks. It is economical, since it can be stored for a longer time in larger quantities. While using, there is less likelihood of waste.


2. Neutral soap:

It is a fairly high-priced white soap of good quality, containing no free alkali.

3. Soap solution:

Soap solutions are used to make a permanent lather on washing waters for all types of cleaning, available in the form of liquid jelly. It is prepared out of bar soap, the proportion being 4 oz of soap to 1 pint of water.

4. Soap Flakes:

It is a type of soap dried and flaked. They are cheap, convenient and effective, pure and safer to any fabric, specially coloured ones.

5. Soap powders:

A large variety of soap powders are available today, which consists of powdered soap and sodium carbonate. The amount of soap present may range from 5 to 30 percent. In the cheaper varieties sodium bicarbonate, sodium silicate and French chalk may be included. They also contain bleach which acts through the release of oxygen. It must be used, carefully, according to the direction on the packet,

6. Disinfectant soaps:

This type of soaps contain about 3 to 4 percent of carbolic acid. The germicidal ingredients in soap of this type and little to its cleaning quality.

7. Solvent soaps:

These are made by dissolving soap in a grease solvent and can be purchased in solid, powdered or liquid form. They are more effective than either soap or solvent, as they:

(a) increase the penetrating power of water for more than soap alone would

(b) can be used in hard water and their action will dissolve lime salts if they are already present,

(c) may brighten the appearance of coloured fabrics and

(d) can be used together with ordinary soap when desirable.

8. Soap nut or Retanut Solution:

Retanut is a dry fruit, excellent for washing coloured silk and cotton, but is not good for washing white woolens or white silks. The retanut solution can be prepared by taking 8 oz retanut to 2 pints of boiling water.

9. Shikakai:

It is a soap pod from ‘Acacia concina’ a prickly bush found in South India like retanut. It is excellent for removing grease and washing coloured cottons and silks.

The luster of silks is retained and the fabric gets back their new freshness.

Properties of Laundry Soap

A housewife often encounters soaps of an unknown quality which should not have any place in laundry work. Good laundry soap especially suitable for washing clothes should be used for cleaning. The quality of soap can be judged in the following way:

1. The soap should be of a clear, pale colour. Dark-coloured soap may contain impurities.

2. It should feel firm when pressed with the finger.

3. Cheap soaps are hard because they contain sodium silicate.

4. A very yellow translucent soap is likely to contain an excess of resin. Such soap may produce an excellent lather, but its detergent properties are insufficient and may discolour white fabrics.

5. On storage, good laundry soap dries with a firm un speckled surface. Soap that develops white crystals on the surface when stored, contain excess alkali, which may be harmful to the fabric.

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