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- You take the greasy animal fat from the bottom of a cooking
pan. You add the grimy wood ash from the fire below. You mix them together
and use the resulting goo to clean yourself.
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- This is the essence of soap. OK, so modern soaps are
a little more sophisticated, but this is essentially how our forebears
would have made it. If you boil and cool the mixture, successively, over
several days, it will eventually go quite hard.
-
- Chemist John Emsley from Cambridge University says it
is quite easy to understand how soap might have been invented.
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- "You can see how if someone was cooking something
on a wood fire and it had fat in it and it boiled over and the fat dropped
onto the wood-ash then the following morning, when they went to clean up
the mess, they would find that when they put water on it that it would
lather and it would clean very well. That was just a simple type of soap."
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- The Pharaohs used soap nearly 3,000 years ago, and it
worked for them in exactly the same way as it works for us today. The secret
of its success lies in what are called amphiphilic molecules.
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- "Soap molecules have a head and a tail," says
John Emsley. "The head likes to attach itself to water; the tail likes
to attach itself to grease. So when soap is put into water, it will find
the grease, it will attach itself to the grease, and it will pull it into
the water and then it can be washed away."
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- Skin diseases
-
- But somehow, this miraculous property was forgotten,
at least in some parts of the world. Instead, medical men from Ancient
Greece and Arab countries used it as a skin balm, as did the Romans.
-
- "We know that the ancient Romans used soap because
it's mentioned in several of their books," says Nina Hall. "But
they didn't use it to wash their bodies, but instead used it as an ointment
to treat skin diseases. And in fact, a soap making factory was discovered
in the ruins of Ancient Roman Pompeii, which was destroyed by a volcano
in AD 79."
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- The Romans did use soap to clean their clothes and they
found it worked best when mixed with urine. In the city of Florence, the
Emperor urged the townspeople to help.
-
- "There were great pots at the street corners where
people could add their own contributions to this," says John Emsley.
"The urine was left for several weeks until it actually decomposed
and gave ammonia, and ammonia is a very good cleaning agent. It will remove
grease and dirt from fabrics."
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- After the Romans, soap making, as an industry, almost
ceased to exist for hundreds of years. But there was an alternative to
boiling up smelly fats and ashes.
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- "One of the simplest ways that people around the
world have found to get clean is to wash using a plant," says Pat
Griggs of the Royal Botanic Gardens at Kew, near London. "Plants are
absolutely amazing for this and there are many species around the world
that contain a substance called a saponin which works in a similar way
to a soap."
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- Plant power
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- Over 100 different types of plants make saponin and sometimes
its found in the leaves of a plant, sometimes in the stem or roots and
sometimes in the berries or other fruits.
-
- "What's happening when we use one of these plants
is that the saponins make a foam when mixed with water, and this lifts
off dirt and grease," says Griggs.
-
- "It works just like an ordinary soap and it's often
very good for washing your hair."
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- In North America, native people sometimes used the root
of the Yucca plant. In India, a shrub called the soap nut bush became very
popular. The nuts are crushed and mixed with water to make the soap.
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- The bars of soap we buy today contain lots of plant material,
plant oil to make the soap itself and plant fragrance to scent it.
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- We are not sure when commercial soap making began again
after Roman times, but by 1200 AD, soap was being made in Bristol in England,
and 200 years later the finest soap was being made and exported from Spain.
This soap was based on olive oil.
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- Revolting mixture
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- "All kinds of oils and fats can be used to make
soap," says John Emsley. "Mutton fat, tallow from cattle, palm
kernel oil, coconut oil, olive oil, palm oil - any fish oil can be used
to make soap.
-
- "If you want the soap to last a long time then you
want to use a saturated fat. If you use an unsaturated fat then the soap
will tend to go rancid after a certain length of time. Soaps made from
saturated fats will last for years, they don't go bad."
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- In times of hardship, when fat couldn't be spared to
make soap, it has been made out bile. Bile is a natural soap, that helps
animals digest the fats and oils they eat. During the First World War,
the bile from slaughtered animals was used as a cleaning agent. This sounds
revolting because bile is a vile green liquid but when it was processed
it looked better and did a reasonably good job.
-
- Today's chemists boil the fat and oil, not with wood
ash, but with sodium hydroxide, sometimes called caustic soda.
-
- "The general principle is to boil up fats with caustic
soda," says Nina Hall. "Water is added and they're boiled for
hours and hours until we get the soap forming. And as well as soap forming,
you get glycerine and the two have to be separated. The soap curdles, a
bit like milk curdling, and it gathers at the top of the big pans in which
it's made and then the glycerine and salts and water settle at the bottom."
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- Over eight million tonnes of soap are produced each year
worldwide and the demand for soap is rising. 50 years ago, it would have
all have been made from animal and plant fats, but in recent years, more
and more synthetic soaps have been coming on the market, particularly for
washing clothes.
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- These are made from petrochemicals. Manufacturers like
the synthetic soaps because the raw materials, the petrochemicals, are
of consistent quality. Consumers like them because they work more efficiently
and do not produce the scum sometimes seen in hard water.
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