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(Practical Approaches to Technical Research in Low-Tech Settings) Using Water Droplets to Rapidly Evaluate the Playability of Magnetic Tapes by Andrew Davis

By LaStarsha McGarity posted 05-28-2019 14:30


(Practical Approaches to Technical Research in Low-Tech Settings) Using Water Droplets to Rapidly Evaluate the Playability of Magnetic Tapes by Andrew Davis.


Presenting on Thursday afternoon, Andrew Davis discussed his preliminary findings on a new method of testing of magnetic tapes. His goal is to develop a method that reduces the time to evaluate each tape, would be effective for various-sized collections, and reduces the need for analytical or playback equipment to be used.

His method is incredibly simple, non-destructive, and cost-effective as well as relatively reliable. By applying a single drop of water to the front side (playing side/ recorded side) and watching the contact angle on the surface, one could determine the playability and risk of a tape. He also tested the back side (carrier only side) and found that the water droplet often behaves in a similar manner to the droplet on the front. To my understanding, application to the reverse may be more suitable for particularly valuable or rare recordings.

Higher contact angles generally correlate with playable tapes and lower contact angles generally correlate with at-risk or non-playable tapes. The difference in contact angle can be viewed solely by the human eye or with a camera. For example, the high contact angle water droplet would look similar to an orange half sitting on a countertop, and the low contact angle would be more similar to an egg in the frying pan. The contact angle seems stable across most of the tested brands and conditions and the method seems to produce more false positives than false negatives. He noted that the test is more effective if the droplet is allowed to remain in contact with the surface for one minute before evaluation.

This method is still being developed and is not perfect. In the discussion of his future goals with the method, Davis mentioned further testing to understand the surface changes that alter the contact angle as the tapes degrade, conducting more research into the brand-based differences, and how to better refine the test to be as qualitatively accurate as possible.

As a student who enjoys working with smaller collections, the resourcefulness of this talk thrilled me. Institutions and collectors could evaluate their collections quickly and identify the most at-risk items to prioritize for migration. Davis describes a rig for holding the tape in place and securing a camera for imaging that cost under $100 (rig only) and a free app plug-in that can determine the exact contact angle, that in tandem help in creating a more uniform process. The computer-assisted method would allow changes to a collection to be monitored over time and tapes to be identified before degradation takes away their sound forever. I thoroughly enjoyed this talk and am keen to see an infographic poster be produced about this method to act as a guide for those evaluating magnetic tapes in future.

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