Soaps are cleaning products that play an essential role in our in our daily lives.
By safely and effectively removing soils, germs and other contaminants, they
help us to stay healthy, care for our homes and make our surroundings more
lovely and pleasant.
Soaps are mainly used as surfactants for washing, bathing, and cleaning, but
they are also used in textile spinning and are important components of
‘’Chemically, soap is the sodium and
potassium salts of higher fatty acids.’’
• Sodium salts of fatty acids are
called hard soaps.
• Hard soap is moderately soluble
• Hard soap does not lather easily.
• Tallow, animal fats and coconut
oils are main source of hard soap.
• Examples: Sodium palmitate ,
• Potassium salts of fatty acids are
called soft soaps.
• A soft soap is easily soluble and
fast dissolving in water.
• Soft soap form lather readily.
• Linseed oil, caster oil, produce
• Examples: Shaving creams, liquids
Rosin is a plant exudation product contain obietic acid.
Colorless rosin used in Laundary soap manufacturing process.
Dark rosin used in manufacture of coloured soaps.
In soap manufacturing , block form of NaOH employed.
In special soft soaps etc. caustic potash(KOH) use in 18.5-
It is used to salting out of soap.
About 12 parts of sodium chloride per 100 parts of oil used In
Binding materials used to improve the cleansing materials of soap,
to improve soap texture , to prevent the precipitates formation in
Certain binding materials are sodium silicate,soda ash, trisodium
phosphate and borax.
The bulk or weight of soap increased by adding some certain fillers without
effecting the detergency.
These are starch, Glaubers salt and pearl ash etc.
Organic dyes and inorganic pigments are used n soap making process.
Common colouring matters are as follows:
• Methyl violet for violet colour
• Bismark brown for brown
• Zink oxide for white
• Chrome green for green
• Eosin for pink colour etc.
The essential oils known as perfumes impart fragrance to soap.
The perfumes may are natural or synthetic.
Natural perfumes Synthetic perfumes
• Sandal wood oil
• Lemon grass oil
• Bergamot oil
• Clove oil
Fats and alkali are melted in a kettle, which is a steel tank . Steam coils within
the kettle heat the batch and bring it to a boil. After boiling, the mass
thickens as the fat reacts with the alkali, producing soap and glycerin.
The soap and glycerin must now be separated. The mixture is treated with salt,
causing the soap to rise to the top and the glycerin to settle to the bottom. The
glycerin is extracted from the bottom of the kettle.
To remove the small amounts of fat that have not saponified, a strong caustic solution is
added to the kettle. This step in the process is called "strong change." The mass is brought
to a boil again, and the last of the fat turns to soap. The batch may be given another salt
treatment at this time, or the manufacturer may proceed to the next step.
The soap in the kettle is boiled again with added water. The mass eventually
separates into two layers. The top layer is called "neat soap," which is about 70%
soap and 30% water. The lower layer, called "nigre," contains most of the impurities
in the soap such as dirt and salt, as well as most of the water. The neat soap is taken
off the top. The soap is then cooled.
Raw oil or fat and catalyst zinc oxide are blended into hydrolyzer. This tower fitted with
steam. Splitting of fat take place continuously in counter current manner at about 250°C
and 40 ATM pressure. Fat globules rise against descending aqueous phase, dissolve
glycerol formed during reaction.
From the top of hydrolyzer fatty acids discharged in flash tank and then led through
heat exchanger to high vacuum and distilled. Distilled fatty acids neutralized with
caustic soda mixer neutralizer.
The soap is dried in high pressure steam exchanger by heating it under pressure
and collected in flash tank at atmospheric pressure. Pasty mass mixed with
required air and cooled to about 65°C.It then cut into bars and slabs as usual.