Compact cassettes, despite their simplicity, often present problems during digitization. This entry will highlight an approach to digitizing compact cassettes that exhibit squealing and speed instability after being rehoused using new hubs, slip sheets and associated components. Since I have started here the only cassettes, to present this problem are labeled “Stanford Bookstore”, so the actual manufacturer of the cassettes is unknown. Currently there are two common treatments for addressing squealing cassettes: playback in a cold environment or lubrication of the tape during playback. This entry describes tape lubrication and is informed by the work of Richard Hess and Marie O’Connell. I will first introduce the collection currently being digitized then briefly highlight an approach to applying D5 (Decamethylcyclopentasiloxane) lubricant to rehoused cassettes. For more information on D5 and soft binder syndrome, visit Richard Hess’s webpage here: http://bit.ly/11SBTVP.
An image of a problematic cassette
Shortly before I started here at the Stanford Media Preservation Lab the University Archives sent a collection of compact audiocassettes to be digitized. The cassettes are from the Michelle Clayman Institute for Gender Research. The organization was originally called The Center for Research on Women and throughout the early cassettes is referred to by the acronym CROW. The earliest cassettes date back to November 1973 and continue to February of 2004. The content of the tapes include conferences, lectures, and seminars. There are some remarkable interviews that were captured with women such as Ursula LeGuinn and Tillie Olsen to name a few. The interviews are available for streaming at the Online Archive of California at the following URL: http://bit.ly/13pzIa1.
The problematic cassettes were identified by the audible squealing coming from the cassette machine transport (in this case Nakamichi CR-7A) and unstable playback speed. Upon confirmation a cassette is squealing and the playback speed is unstable (we currently digitize cassette’s in a parallel 4 to 1 configuration) I would check that this also is the case with playback in in the other type of cassette machine in the Stanford audio lab, the Tascam 122MIII. Upon confirmation of universal (for our purposes) playback instability rehousing is the common next step. The cassette is split either by unscrewing the housing or carefully splitting the housing if glued (or possibly splicing onto other leader and reeling into new housing if ones lab is so equipped). In the case of problematic Stanford Bookstore tapes their housings are assembled with adhesive bonding that require careful splitting (as a side note all cassettes are fast forwarded and rewound before the initial attempt at playback to catch any possible problems and to create a high quality tape pack since often the cassettes have not been played in 30 years).
After the cassette has been split and the cassette reels are available I would then remove the reels and place them in a new housing. The next step would be trying playback with the original hubs. If this does not address the squeak then the hubs also would be replaced. Most often with this batch of cassettes rehousing did not rectify the problem. As a side note currently in the lab there are two different replacement cassette housings available to use, both housings consistently returned similar results with the cassettes in question.
So at this point the cassettes have been tried on several machines, are in new housings, with new hubs, and different housings have been tried with the same run of cassettes. Often still the squeaking and playback instability remains (often with enough friction to stop the cassette playback entirely). At this point it was deemed useful to apply a small amount of lubricant to the cassettes. This is where an interesting approach to application has been developed.
The rehoused cassettes would have one half of their new housing removed and a small hole drilled in it with a 1/8-inch drill bit. The hole is placed next to the roller on one edge of the cassette (Figure 1). Sometimes one hole would be drilled on both edges of the cassette depending on amount of lubrication needed; usually a light coating during playback of the cassette on one side would leave enough residual lubrication for playback on the other. It is always worth appreciating the original thoughtful design of equipment and carriers and to this end it is important to keep in mind that the drilling location should impact the ease of tape playback as initially designed as minimally as possible.
Figure 1. Image of cassette housing drilled for applicator use. In this case lubricant application was necessary for both sides of playback where as sometimes playback of one side with application left enough residual lubricant to not require re-application during playback of the opposite side
Then a cotton applicator of the type used for cleaning open reel tape machine heads is soaked in D5 (Figure 2). The cassette housing is re-assembled after cleaning away any plastic debris from drilling. The cotton applicator is then carefully placed in the hole and the end trimmed off (Figure 3). (The 1/8-inch size worked well for our cotton applicators, depending on what you have on hand it may require a different size bit). Next the tape would be placed into the cassette machine transport and played back, Usually this would allow for playback of a cassette. Occasionally a cassette would still not playback well and usually benefitted from a few days rest before attempting another playback with the lubrication process repeated.
Figure 2. Cassette and Puritan PurSwab model cotton applicator used in the process
Figure 3. The red circle highlighting the inserted and trimmed applicator in cassette housing
While this process is not new this mode of application might be unique. There were 0 failures of the application process (no cotton coming off, no failure of the underlying wood of the applicator, or any other mechanical damage). So far this approach has been used with 10 cassettes and with further applications of this process refinement may occur.
Possible areas of further exploration include the affect on tape tension of various placement locations of applicator, the long term effects of different types of lubricant (i.e. silicon, D5, LAST, and so on), and trying different types of applicators