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Story: Salt

New Zealand is surrounded by sea water, but attempts to produce salt were unsuccessful for a long time. It was not until the 1940s that an enterprising businessman saw the potential in Lake Grassmere, in the north of the South Island. Exposed to sun and wind, this dramatic site, with its pink ponds and dazzling salt mountains, now produces about half the country’s supply.

Story by Carl Walrond
Main image: Crystallisation ponds at Lake Grassmere

Story Summary

All images & media in this story

What is salt?

Salt (sodium chloride) is the main mineral in sea water. It is also found under the ground, and in our bodies.

What is it used for?

Salt is used to flavour food, and to preserve butter, meat and fish. It is also used in industry – in textile dyes, bleaching paper and curing leather.

Do we need to eat salt?

Our blood, sweat and tears contain salt, and we need to eat small amounts to stay healthy. But many people eat too much salt, which can cause high blood pressure and other problems.

Since 1924, iodine has been added to New Zealand table salt. In the past, many New Zealanders lacked iodine, and as a result, some had goitre – an enlargement of the thyroid gland causing a swelling of the neck. Now the disease has almost disappeared.

Salt in New Zealand

Māori got their salt by eating seafood. The early settlers had to import it, and a few people tried unsuccessfully to extract it from the sea. Salt was not made locally for many years.

Early days of salt making at Lake Grassmere

During the Second World War, Christchurch businessman George Skellerup needed salt to recycle old rubber. In 1942 he decided to start a salt works at Lake Grassmere, in the north of the South Island. The conditions were ideal for getting salt from sea water: the lake bed was large and flat, rainfall was low, and there was plenty of wind and sun to evaporate the water. By 1970 the salt works were producing almost 52,000 tonnes of salt a year.

How is salt made at Lake Grassmere?

By 2005, about half of New Zealand’s salt was being produced at Lake Grassmere. There are several steps in the process:

  • Sea water is pumped into the lake.
  • Wind and sun evaporate the water, leaving brine (salty water).
  • The brine is moved to concentration ponds, where the salt content increases.
  • Over winter the brine is pumped into holding ponds.
  • Each October it is pumped into crystallisation ponds, where salt crystals form.
  • The crystallised salt is scooped up, washed, and stacked in huge piles for delivery.

Lake Grassmere’s pink ponds are a unique sight – their colour comes from the algae and brine shrimps that live in salty water.

How to cite this page:

Carl Walrond, 'Salt', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/salt (accessed 19 November 2017)

Story by Carl Walrond, published 12 Jun 2006