- Primary spotless use: Natural all round cleaner, disinfectant and deodoriser
- Dislodges caked dirt, dissolves grease and loosens stains
- Other uses: Preservative, flavour enhancer, antiseptic, water softener, melts ice
- Main cleaning action: destroys bacteria, absorbs and breaks down grease and grime
- Obtained mainly by evaporation of brine and mining of rock salt
- History has been significantly influenced by the use and trade of salt
- Small quantities are essential for life and salt exists in all animal cells
One of the most useful substances on earth, salt is also very cheap. Like lemon juice it is good for the skin and circulation and, like other natural cleaners, is both a deodoriser and a disinfectant.
An excessive intake of salt is harmful and linked to many health problems. But salt is one of our basic tastes and in small quantities it is essential for life.
Coarse non-iodated sea salt, which is available at most supermarkets in large bags, is normally cheapest and is suitable for many household cleaning  uses. (Swimming pool shops can be another source of bulk quantities of salt at good prices.) Kitchen salt, medium salt, fine salt, or table salt can all be used too (though not in the dishwasher  as they are iodated). Because they are finer and therefore less abrasive, they are better for use on shiny or delicate surfaces. Natural salt is best for culinary and medicinal uses (and also better for personal care  if possible).
Salt (or common salt, as many other compounds are salts) consists mainly of sodium chloride (NaCl). However in its natural form about 16% is made up of a range of other minerals and trace minerals, depending on its origin. It is found throughout the planet, dissolved in the oceans and in mineral deposits from ancient seas, as well as in all animal cells. Salt dissolves readily in water (brine) and occurs in crystals of various sizes.
The white salt commonly sold for human consumption has had all the minerals other than sodium chloride removed, and iodine added, as well as various other chemicals to improve flow and prevent caking. Natural sea or rock salt is also available, especially at health food outlets. It can appear in various colours ranging from pure white to grey or pink, depending on the particular minerals naturally present in addition to sodium chloride.
Salt is obtained mostly by evaporation of seawater or other brine into crystals (producing solar or sea salt), or by mining of rock salt (sedimentary mineral beds left by dried up lakes or seas). Underground salt deposits are shaft mined in solid form (rock salt) or solution mined, where water is pumped through the rock salt to dissolve it. The brine is then pumped out and dehydrated (producing evaporated salt). It is produced all over the world, the most in China, followed by the USA.
Apart from its use as a condiment, our most ancient use for salt has been as a food preservative. Salt draws water from the cells of bacteria and other micro-organisms, preventing them from spoiling food; the same thing applies when it is used to prevent infection of wounds, or to disinfect home surfaces.
Adding salt to water lowers its freezing point. This makes salt very useful in defrosting icy surfaces – a small amount of salt will weaken ice enough to remove it easily. (Salt was once a precious, rare commodity. Today, 51% of the world’s salt production is used to de-ice roads. Much of this salt ends up in fresh water, harming aquatic life.)
Medically, salt is useful in preventing dehydration (but too much salt causes water to be drawn from cells), fighting sore throats, clearing sinuses, soothing stings, cleaning wounds, and for digestive trouble. See here  for a look at salt’s place in medicine through the ages.
In the body, salt forms a part of all cells and is required for many processes. It transports nutrients in and out of cells, helps regulate blood pressure and the propagation of nerve impulses, and helps the brain communicate with muscles in order to move. It is also the body’s own natural anti-depressant. Because it dissolves so readily in water, salt tends to leach from land into water via rainfall, so that little remains in soils. Because of this relative scarcity on land and its importance to animals, plant-eating land animals, including humans, have developed a special taste receptor for salt. (Of course in modern diets this can be a problem as salt is no longer a rarity, with many foods awash with an excess of processed salt.)
Salt is useful throughout the home in household cleaning , and its benefits extend to many personal care  uses too. Salt used on the skin smoothes, detoxifies and stimulates circulation. It has some similar cleansing uses to bicarb  and can be used together with it or as a cheaper alternative for some jobs. Also see here  for many more uses for salt.
There is evidence of salt being extracted from salty springs by Neolithic people from 6,050 BC, and salt was being harvested from the oldest verified salt works at Xiechi Lake in China from at least 6,000 BC.
Throughout history, access to salt has allowed societies to flourish and trade. Salt once traded at an ounce of salt for an ounce of gold. The ability of salt to preserve food allowed food to be stored and transported, transforming people’s diet and access to foods. The history of human societies is linked closely to the use, trade and control over the supply and transport of salt. Settlements arose, societies flourished and wars were fought because of it. See for example here  for more about salt’s role in history.
People have used salt for cleaning by rubbing it on surfaces from at least medieval times.