Background: The Preservation Research and Testing Division have been investigating common cleaning solutions for lacquered discs exhibiting moderate and severe degradation. Castor oil was a typical plasticizer used in lacquered discs, and is known to break down over time into specific fatty acids. These fatty acids migrate to the surface forming an oily or waxy film that makes the discs difficult or impossible to play without cleaning. Water-based cleaning solutions are currently in use at the Library and at other preservation institutions. Current research includes studying a series of formulations, both commercially available and mixed from ingredients on-site, to assess their ability to remove the fatty acid containing exudate without leaving a residue.
Project Description: The often white exudate found on lacquered discs was collected from a range of Library of Congress collection discs and analyzed using gas chromatography and mass spectrometry (GC-MS) to identify the relative amounts of fatty acids present. Once identified, reference standards of the fatty acids were mixed with an array of cleaning solutions containing non-ionic surfactants, buffers, chelating agents, and ammonium hydroxide, and the resulting solutions compared for their relative ability to dissolve the fatty acid mixture using GC-MS. The cleaning solutions were placed in contact with degraded discs and photographic and image analysis utilized to assess the ability of the cleaning solutions to dissolve the exudate. The degree of residue remaining after the cleaning was evaluated by placing a small amount cleaning solution on a glass slide and either leaving the test site wet, or allowing it to dry. The wet or dry spot was then rinsed with water, imaging the spot after each rinse. Each cleaning solution was also put directly in contact with a lacquered disc surface to determine whether the cleaning solution removed non-fatty acid components of the disc.
Non-degraded lacquered discs.
Degraded lacquered discs, with the degraded disc exhibiting severe accumulation of plasticizer degradation products (stearic and palmitic acids) on the surface.
Outcomes/Findings: The study resulted in the following key findings:
- Both stearic and palmitic acids were found on the surface of all degraded discs.
- Commercial formulations designed for cleaning discs, containing non-ionic surfactants tended to perform better than lens cleaners and home-made mixtures of surfactants with water.
- The addition of ammonium hydroxide often showed an improvement in solubility of fatty acids; however this component is still being evaluated to assure its safe use on discs.
- Cleaners with fewer components rinsed from either the wet or dry state with fewer rinses.
- Buffers, in particular, once dried on the surface required the most rinsing to remove.
- All solutions were removable with deionized water rinsing.
Acknowledgements: Ellen Hartig, and Motion Picture, Broadcast and Recorded Sound Division staff members Eugene DeAnna, Dawn Frank, Brad McCoy.
