sweat v Cp OED ~ v 10 b 'of products set aside to exude their moisture.' In the curing of fish, esp cod, to exude salt; to spread thoroughly through the fish by pressure of the pile, WORK.
[1663] 1963 YONGE 58 When well dried, it's made up into prest pile, where it sweats; that is, the salt sweats out, and corning, makes the fish took white. [1766] 1971 BANKS 135 When the Fish are tolerably dry they Put them in Round Piles of 8 or ten Quintals Each Covering them on the top with bark in these Piles they remain 3 or 4 days or a week to sweat after which they are again Spread & when dry Put up in Larger heaps Covered with Canvass & Leit till they are put on board & ready for the Mediterranean trade. 1819 ANSPACH 437 After the fish has been first spread on the flake, four good days out of seven, (which is considered as better than four successive good days. because it then works or, as the fishermen express it, sweats the better), will be sufficient to save it from any material damage. 1861 Harper's xxii, 595 After this they are piled in 'kenches' again for a day to sweat' them—that is to remove remaining moisture—and are again thrown upon 'flakes' for a day. They are then ready to be stowed in bulk in the vessel.
