Surface workers in the mill were paid weekly wages. Poor labour relations at the time led to an unofficial strike in 1942; the men on weekly rates eventually received an increase of 2 shillings per day following a similar settlement in the West Cumberland iron mines. In 1959, when the Greenside Mine was about to close, it was used as the site of an experiment to test the seismic detection of large underground explosions. The Partial Nuclear Test Ban Treaty of 1963 was the result of eight years of negotiations, following a proposal for a ban on nuclear tests made by the Soviet Union in 1955. The biggest obstacle to a treaty was the issue of verifying that all parties complied with it, and the Western powers were determined that any agreement reached could not be violated in a clandestine manner. One of the issues at stake was the possibility of disguising explosions in large underground chambers by decoupling the explosive from the rock. This idea was developed by Dr Albert Latter in 1959. With negotiations underway, some small-scale tests were made immediately to determine whether decoupling could work to disguise the size of an underground explosion. After an initial pair of small explosions in clay, a larger programme of testing was undertaken, first in the Excelsior Tunnel beneath Kit Hill in Cornwall, followed by larger explosions at a salt mine in Louisiana in the USA, and finally two explosions in solid andesite rock at Greenside Mine. The UK part of this programme was called Operation Orpheus  The first explosion at Greenside involved the detonation of of TNT placed on a wooden frame in the centre of an ellipsoidal chamber long and in diameter. This was the decoupled charge. It was detonated at 22:30 on 19 December 1959, and the seismic signals were detected at six locations up to away. The second explosion, of of TNT packed into a small chamber long and in diameter, should have followed 30 minutes later. This was the smaller, coupled charge, in order to compare its seismic effects with the larger decoupled one. However the first explosion destroyed the cables and control equipment needed to detonate the second charge. The second test was further delayed by a mining accident, and eventually took place at 19:00 on 29 April 1960. But the tests were conclusive. The smaller charge gave rise to a larger seismic signal and showed that the effect of the decoupled charge was attenuated by a factor of between 10 and 30. Control of Greenside Mine for the tests was taken over by the United Kingdom Atomic Energy Authority at the end of November 1959.