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Re: arsclist Cassette Sticky-Shed

Fatty-acid esters are used as lubricants for tape and floppies. These
are preferably used as bulk lubricants dispersed in the magnetic layer,
but some manufacturers used the less desirable method of topical
(surface) application. More recently, some manufacturers have mixed
styrene lubricants into polyurethane binders.

Use of other lubricants is risky, since they can actually increase
friction of the polymer-to-polymer contact, along with "brown stains" on
the read-write head.

Lubricants alone are undesirable, and responsible manufacturers include
an oxidation inhibitor, a metal deactivator, and a hydrolytic inhibitor.

Media Sciences, Inc.

James L Wolf wrote:
> Last week I posted the message that started this thread. I appreciate
> the responses. Here's some follow up and detail.
>   The tape in question was mass produced for the Takoma/Chrysalis
> company in 1980 or 81 and was still sealed until last week. The tape
> stock is medium light colored, typical for mass-produced cassettes of
> the era and the shell was without screws.
>   I went ahead and baked the cassette (in the shell) for about 7 hours
> total. The squeeling remained but the tape no longer deposited residue
> on the guides and heads, as it had the first time I played it. At the
> suggestion of Larry Appelbaum, I transfed the cassette to another case,
> in case the original was warped or otherwise damaged. No change.
>    Larry mentioned another possibility, that the tape LACKS lubrication
> because it dried out over time and that baking would only exacerbate
> this problem. A silicone spray might solve this but with consequences
> for equipment. What is known about this condition? Or could there be
> some other explanation?
>    Others I've talked to in the Library of Congress have not dealt with
> this issue much because they have had few occasions to deal with
> cassettes. I agree that some sort of pooling of tape stock information
> would be enourmously helpful.
> James Wolf
> >>> smolians@xxxxxxxxx 01/06/03 10:18 AM >>>
> As to cassettes.
> Real brands use a different formula for the soup that, when spread on
> plastic sheets and slit, becomes the cassette tape.  Lubricant issues at
> slow speeds are different, among other things.
> Have any tapes not back-coated developed sticky-shed?  As far as I've
> been able to determine, no cassette tapes were back-coated.
> It would be useful to know what cassette brands and product numbers have
> developed sticky-shed. If there is a date f recording as well, that
> could contribute to identifying those at risk. Of course, this does not
> "date" that tape but gives some idea of when it was in use.
> Steve Smolian

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