A Hefty Challenge for IRENE: Working with Delaminating Lacquer Discs
Over the past few months, we’ve successfully recovered audiofrom a wide range of formats and conditions. In this post we’ll discuss our most difficult assignment to date – delaminated lacquer instantaneous discs.
Glass-based transcription disc, WNYC Broadcast, April 22, 1944, Junior Citizens Service Corps Disc Courtesy New York City Department of Records / Municipal Archives
Unlike vinyl or shellac discs or wax cylinders, lacquer audio discsare composed of two distinct materials – a rigid structural disc commonly made of aluminum or glass, and a coating of soft nitrocellulose lacquer. For a variety of reasons, the lacquer can separate from the base in a process we call delamination.
Delamination can often be initiated or accelerated by improper storage or handling. As the lacquer lifts from the disc surface, it becomes brittle, and can crack along the edges. Individual pieces can warp and curl, and separate entirely from the disc. Mechanical playback can further damage the disc, and is unlikely to produce a successful transfer.
Unfortunately, even IRENE’s impressive capabilities do not make this condition easily manageable. Thanks to a loan by the New York City Department of Records and the New York Public Radio Archives, we’ve been able to conduct experiments with a large collection of delaminating lacquer discs which cover the full spectrum of failure. We’ve included some images below to help illustrate the challenges of working with these discs.
This is a sample of a typical lacquer disc as imaged by IRENE. The vertical lines represent the audio grooves. Sometimes the lacquer partially delaminates from the base without cracking, but this would not change how the disc looks under IRENE. (Click on the images to enlarge.)
As the delamination progresses, the differing thermal expansion rates of the surface and base cause the surface to stretch and tear. For this reason, it’s very important to limit variation of temperature and humidity in storage environments. In this image, you can see the lacquer has split and separated, but the pieces are relatively flat. (The WNYC disc shown above.)
As the flakes age, many of them begin to curl and warp. If the warping creates a vertical variation greater than the depth of field of our camera, focus is lost at the extremes. (The WNYC disc shown above.)
As this condition progresses, pieces of lacquer – at this point small flakes – will begin to separate completely from the base, and extreme care must be taken to ensure they are not lost or further damaged. The flakes can be carefully arranged back on the disc for imaging, but at this scale it’s difficult to align them perfectly, or impossible if any of the individual pieces are warped or stretched. (The WNYC disc shown above.)
If all goes well, IRENE is able to image the disc with decent focus and alignment, but this is not the end of our task. The resulting images are fragmented, and must be tracked manually in the computer so that the software sees a continuous groove. This is a difficult and very time-consuming process. (The WNYC disc shown above.)
For comparison, this image was taken from a lacquer disc in typical condition. The grooves are smooth and parallel, and tracking can be automated. The final result will be clear audio. It's best to prioritize delaminating discs for digitization before they fail completely. The sooner a degrading disc is digitized, the better the sound quality and the lower the cost of the transfer.
Even though the IRENE system was able to get audio from parts of this particular disc, the message of this post is NOT that ‘delamination is no longer a problem.’ Once the process of delamination has begun, it’s almost inevitable that it will progress over time, eventually making the audio unrecoverable. We encourage you to carefully survey your collections and consider reformatting lacquer discs that are in the beginning stages of delamination as soon as possible. (It is important to pay particular attention to WWII-era transcription discs, many of which have a glass substrate. Aluminum was in high demand for the war effort, so glass was used. The glass-based discs are far more susceptible to delamination than aluminum-based discs.)
[NOTE: NEDCC plans to work with objects conservators to research methods of stabilizing delaminating discs to improve image capture using IRENE, so that we might be able to bring back to life media that today is too far gone to digitize.]
IRENE was able to retrieve the following audio from the inner grooves of the delaminating lacquer disc pictured above.
LISTEN:
Glass-based lacquer transcription disc WNYC Broadcast, April 22, 1944, Junior Citizens Service Corps Disc Courtesy New York City Department of Records / Municipal Archives [This recording features legendary children’s radio personality Ireene Wicker, “The Singing Lady,” who received many awards (including radio’s highest honor, the Peabody Award) during her long career.]
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