Playing Metallica shows can be pretty grueling. In fact, so much so, that Jason Newsted reveals that he used to exhaust his supply of basses on tour as his sweating during shows tended to short out the instruments. That led to the bassist resorting to his own "sweat test" in order to determine the durability of the instruments he was using on tour.

Speaking with Bass Player, Newsted recalled, “For Load, I used a '58 P-Bass and a 1981 Spector NS 4-string. The Spectors were built really well, played well and sounded excellent, but I had a lot of trouble with sweat getting inside. All of my instruments had to be salt-water proofed.”

“We’d done an outside show on the last tour," he continued. "And by the end of the gig, there was one functioning bass out of six – bad news. And when a bass going through 250,000 watts of PA all of a sudden shorts-out, people are not happy.”

The bassist reveals that by the time they started their 1996 tour, he had started a friendship with Roger Sadowsky of Sadowsky Guitars, and it ended up that Sadowsky's basses became his instrument of choice after undergoing his sweat test.

“When I was trying to figure out who was going to build my basses for the tour, I’d have to test each bass. I'd fill up a big tub with super hot water, dump in some salt and submerge the bass," revealed Newsted. "Then, I'd take it out of the tub and put it in front of a coil heater for a few minutes. I'd repeat this same process three times with each bass. Then I'd beat the crap out of it for a while in my studio, and finally I'd let it sit on a stand for a couple of days. Usually, the bass corrodes and doesn't play anymore. None of the basses passed that test except for the Sadowsky.”

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Sadowsky elaborated on the issue that Newsted was experiencing, explaining, “Jason voiced his concerns about moisture and reliability. Apparently some of his basses were having an intermittent output, and when his tech would remove the output-jack plate, water would literally run out of the control cavity! It turns out the humidity levels at the shows are so high from the heat, water runs down the front of the amplifiers! And moisture was building up inside the control cavities from condensation."

The guitar maker revealed that they came up with a solution to put a thin rubber gasket on the back of the control-cavity plates and underneath the football-shaped output-jack plate. They also sealed the holes going from the pickup cavities to help keep any moisture from flowing in.

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