Staff at the salt mine are working seven days a week to cope with demand
More than 30,000 tonnes of salt is being dragged from the bowels of the earth under County Antrim every week as part of the battle to keep the UK's road network open.
Just outside Carrickfergus, salt which formed during the Triassic period is brought into the light of day by the Irish Salt Mining and Exploration Company.
The Northern Ireland mine is one of three main mines that supply the needs of the UK's transport authorities, with the other two being the Salt Union's Winsford Rock Salt Mine in Cheshire and Cleveland Potash in Teesside.
De-icing or gritting salt is nothing like the ground white grains used to season food.
Made from crushed rock salt, it is brownish in colour and resembles gravel.
The rock salt comes from a vast echoing maze which stretches some 30 miles and goes 1,200 ft underground.
The seam is part of a salt bed stretching to Russia, and was discovered in the 1800s as miners searched for coal deposits.
Instead they found 220 million year old salt, left by the evaporation of a saltwater sea under a desert sun.
salt in Carrickfergus
has been mined since 1965, and while full of impurities it has been invaluable in keeping roads in Northern Ireland, Scotland, England and even in the United States clear during periods of extreme cold.
Councils can pay between £22 and £27a ton
for salt originating in Carrickfergus, a BBC Freedom of Information request found last year.
Staff are working a seven day week to cope with demand, a company spokesman said.
"We're working seven days and mining 30,000 tonnes," he said.
"It is all going to local authorities, we've stopped supplies to the private trade."
He said that current demand was very high and that in previous years output had varied with spells of milder weather, but that the long spell of sub-zero temperatures has kept production levels high.