Cutting Up: Stereophile's Liszt Piano Sonata LP Page 4
Another benefit of this is the increased amount of land between the grooves, which helps to cut down on the groove malformation that produces pre-echo. Think of a lacquer as a plastic substance just barely removed from a liquid—it tends to flow a bit. When the grooves are tightly spaced, the more dynamic side of a single groove can dominate the opposite side—the lacquer will try to achieve an equilibrium, resulting in the ghostly intimation of the music yet to come, or that just passed.
This tendency for lacquer to "flow" is one reason why AcousTech located the cutting room at the same location as RTI's plating facility. Lacquers can begin to be plated within minutes of having been cut.
Gary Salstrom, who runs RTI's plating operation, is part chemist, part technician, and part alchemist. We watched, awed, as he processed our lacquers. The first step is a thorough cleaning. The cutting process itself raises oils out of the lacquer, and it is vital to remove them: The electroplating process replicates the lacquer's surface on a molecular level, so it is important that nothing—not even an oil—be present upon it.
The lacquer is soaked in a mild detergent solution for 30 minutes, then rinsed in filtered tap water, rinsed again in de-ionized water, and yet again in stannic chloride solution, for 45 seconds. Finally it is ready to be plated with silver, to give the surface a conductive medium for the nickel to adhere to in the plating baths.
The cleaned lacquer is fixed to a spinning table in the spraying booth, where a multinozzle head, mounted on a pendulum, sprays it with a mixture of dextrose, sodium hydroxide, and silver nitrate. The dextrose acts as a reducing agent, precipitating the silver nitrate into a layer of silver that adheres to the surface of the lacquer. (Common wisdom has it that the layer is about one molecule thick, but Gary tells me he's never actually measured it.)
Watching the black lacquer turn into a reflective silver disc after just a few rotations is a magical experience, rather like watching a photographic image's rush toward reality in the developing tray. No matter how many times I witness it, I always feel some degree of awe.
Why silver? Salstrom explains, "We're trying to duplicate the groove cut into the lacquer, and silver is the best conductor that's affordable. It has a lot of desirable qualities. First, we get an even spread of amperage from the center to the outside edge. You can also get silver that is very pure—impurities will show up sonically—and it can be applied in an incredibly thin, grainless coating. When I was at Wakefield [a 1980s-era plating and pressing facility in Arizona—WP], a chemist and I developed our own silver spray. It was so hot there we had problems with the ammonium hydroxide escaping from the bottle of silver spray, which meant that metal started dropping out and forming solids at the bottom of the bottle. So I started mixing my own.
"Now I get silver nitrate crystals from a company in Chicago because dissolving my own silver 'coins' in nitric acid can be hazardous, but that's the only thing I have made up for me. And even though that results in very pure silver, I use a micropore filter before it goes into the lines feeding the sprayhead."