Occasionally, optional work such as cleaning or rehousing is proposed. Such work may not be absolutely necessary for the digitization of the audio content, but is offered as an additional service to improve the signal quality or preserve the audio carrier. If proposed as an option, this procedure will be described in detail and we will only proceed upon your authorization.
Introduction: Why we clean lacquer discs
IRENE derives audio from images. It follows, then, that we can improve the quality of the audio by improving the quality of the images. ‘Quality,' in this sense, is our ability to clearly see the features of the disc that contain the audio content.
When a disc is clean, we see crisp vertical lines moving side to side with audio. When a disc is dirty, however, the crisp lines fade into shades of gray caused by the diffusion of the light into a layer of dirt and oil or plasticizer exudate. This lack of image clarity disrupts the IRENE analysis resulting in a noisy transfer. We can improve the resulting transfer by cleaning the disc prior to imaging.
|
|
In designing a treatment to safely and effectively wash the relatively sensitive lacquer discs, we reviewed all available literature, and consulted with audio experts and conservators. The following method has proven safe and effective in our testing.
Please note that this treatment is entirely optional, and will never be performed without a client’s permission.
Step 1: Start with a dirty disc
its sleeve was soaked in a flood.
|
to lacquer discs. As these discs age, some formulas exude a waxy substance, mostly palmitic and stearic acids, as the castor oil plasticizer breaks down. |
Step 2: Inspect the surface for damage
Each disc is inspected for damage before cleaning. A disc showing any signs of cracking, crazing or delamination will not be cleaned, as water and physical contact can accelerate the failure.
Step 3: Protect the label area
We encapsulate the label area with a 'Groovmaster' label protector before wetting the disc. Unlike commercial recordings, in which the label is typically pressed into the substrate while hot, lacquer discs used adhesive labels, which can dissolve in water and separate from the disc. The Groovmaster handle supports the center of the disc during cleaning, keeping the disc surface from sitting in the sink. Similarly, markings on paper labels, or grease pencil markings directly on the disc can be damaged by water. The Groovmaster prevents water from getting to this area during rinsing and washing.
a 'Groovmaster' label protector before wetting the disc. |
the center of the disc during cleaning
|
Step 4: Rinse the disc
A preliminary rinse will get rid of loose particulate matter and begin softening the layer of dirt. Using distilled or deionized water prevents minerals from depositing on the disc surface. As always, gloves are worn when handling the disc.
Step 5: Spray and wipe
The disc is then sprayed with a soapy mixture of deionized water and .5% Tergitol 15-S-7. Tergitol is a mild surfactant that lowers the surface tension of water and allows dirt that is loosened by wiping to be easily rinsed away.
mixture of dionized water and .5% Tergitol 15-S-7. |
For discs exhibting plasticizer breakdown, a separate solution of .5% Tergitol and .1% Ammonium Hydroxide in water is used. The ammonia breaks down the fatty acids of the exudate without harming the nitrocellulose lacquer.
|
|
The soapy mixture is allowed to sit on the disc for 2-5 minutes. The disc is then lightly wiped in the direction of the grooves with a clean ‘Disc Doctor’ record brush.
Step 6: Rinse again
The disc is then rinsed again, thoroughly,
with cool deionized water, to remove
all of the dirt and cleaning solution.
Step 7: Dry
The disc is patted dry to reduce the total time of exposure to water. (The lacquer is hygroscopic, and should never be left to soak.) A microfiber cloth is used to prevent fibers from coming loose and sticking to the disc.
The disc is then placed in a plastic-coated drying rack until absolutely dry, about 30 minutes. Never re-sleeve a wet disc, as the moisture can cause the sleeve to mold and damage the disc (see step 1).
|
|
Step 8: Resleeve
Finally, the clean, dry discs are re-housed in fresh, archival sleeves. This is important! There is evidence that old acidic paper sleeves can initiate or expedite the plasticizer breakdown, and contribute to further degradation of the carrier.
|
Results
Sources:
1. Identification of a Safe Cleaning Solution to Treat White Crystalline Deposits on Lacquer Discs (Presentation) - Eric Breitung & Elli Hartig, Library of Congress Preservation Research and Testing Division. Presented at the ARSC Annual Conference 2014.
2. A Review and Discussion of Selected Acetate Disc Cleaning Methods: Anecdotal, Experiential and Investigative Findings – Paton, Young, Hopkins & Simmons. Published in the ARSC Journal, Vol. 28:1 (1997)
3. Cellulose Nitrate in Conservation – Charles Selwitz. Published by Getty Conservation Institute, 1988.
4. Preservation and Storage of Sound Recordings – A.G. Pickett & M.M. Lemcoe. Published by Library of Congress, 1959.