Here’s an OLD tape splice on a 1965 7387 Kodachrome print of Ben Van Meter’s Up Tight… L.A. is Burning… Shit (1965):
Some brands or batches of splicing tape can have the effect you see here, often developing over many years, which is a kind of tarnishing of the silver in the print’s soundtrack. Thankfully, it seems to be the minority of splicing tape stock that can have this deleterious effect, at least based on my own observations over the years. Also based on those observations, this reaction seems to only really affect the silver in film, which is why it’s visible in the soundtrack here, but not the image, because even though the image is black and white, it’s on color (Kodachrome) print stock. Color prints are typically bleached of their silver content so only the color dyes remain, while conversely the silver would be retained in the soundtrack area to ensure a nice, dense, even track exposure, for consistent and good quality sound reproduction.
Elsewhere on this site you might’ve seen my write-up on preserving Mike Henderson’s UC Davis class film Will She Get Over It? (1971), in which I talked about this same kind of tarnishing. In Mike’s film, it DID affect the image, as it’s a b/w reversal film, the image being made up entirely of silver. I thought Ben’s print was a good example of how this deterioration can affect ONLY the track and NOT the picture, due to the respective presence/absence of silver in track/picture. So something in the chemical makeup of this tape just doesn’t get along with silver, apparently.
Myself, I’ve actually run into this terrible splicing tape and its eroding effects most commonly on prints deriving from the former Creative Film Society collection (which is where this particular print lived for many years before going back to Ben). CFS was a significant early distributor of experimental and independent films in Los Angeles, begun by Robert Pike in 1957. And apparently, whatever splicing tape they used for repairs over the years was not terribly archivally friendly stuff.
As for silver soundtracks, these days, most 35mm color prints tend to be printed with silverless cyan dye tracks (intended for projection on projectors equipped with red optical lamps), but 16mm is generally still printed with a silver track via a track application process that allows the track’s silver content to be retained and protected while the silver in the color image is bleached away.
By the way, Ben Van Meter is appearing at a rare program of his films at the De Young Museum in San Francisco on August 18, 2017. If you’re in the area, don’t miss it! It will include Up Tight…, a new print of his notorious first film The Poon-Tang Trilogy (1964), and restorations I worked on of his films Colorfilm (1965), Bolex Peyote Bardo (formerly known as Olds-mo-bile) (1965), and SF Trips Festival: An Opening (1967), which I previously wrote about here.