Salt is produced from deposits of rock salt, from sea water, and from the waters of salt lakes and springs. The method of producing salt depends upon the source it is taken from.
If taken from a sea or lake, the water must be evaporated and the grains of salt collected. Much of the salt used for preserving foods is called solar salt because the moisture is dried off by the sun.
Most table salt is made from rock salt, which is found in great beds in many parts of the world where ancient seas have dried away. The usual method of getting rock salt is to drill wells down to the salt beds. Pure water is pumped in through a pipe; when the water dissolves the salt, the brine formed is brought to the surface through another pipe. This method is called hydraulic mining. Evaporation is forced, and the grains of salt are dried in long rotating cylinders through which hot air is passed. The dried, bleached, white grains are then screened for table use, dairy purposes, and packing.
Because much of the world’s food is raised in areas where iodine is lacking, saltmakers add a small quantity of iodine to the table salt to make a product known as iodised salt. A little calcium phosphate is added to make the salt freeflowing.
Most of New Zealand’s salt requirements are obtained from Lake Grassmere, on the South Island’s Kaikoura coast. About 70,000 tonnes of salt is produced there annually.
