Hi Eric,
I've considered the use of a diluted solution of our MRC for this application but don't have suitable tape for evaluation nor a way to determine its effectiveness. I would start with a strength that is 1/4 to 1/2 the recommended concentration for cleaning vinyl discs. If there is any suggestion of harm to the tape, we can prepare the solution without the very small amount of Reagent Grade n-propyl alcohol normally in the formulation.
Regards,
Duane Goldman
On Oct 23, 2014, at 10:40 AM, Breitung, Eric <[log in to unmask]> wrote:
> I agree with Karl - Stearic acid can often be a hydrolysis product of lubricants such as castor oil. This is found on much older media like lacquered discs as a white exudate, but it is nearly always paired with palmitic acid when it comes from castor oil, so I’m not sure what lube they were using to get just stearic acid.
>
> Careful using some of the solvents on the list provided for two reasons: 1) toxicity – like trichloroethylene = likely carcinogen and 2) stripping more than just the stearic acid from the surface. If you only need to get one play out of the tape, stripping the surface with isopropanol may work and allow a play, but I’d definitely try it on a small area and let it dry to see if there’s loss of adhesion of the magnetic particles – or any other affect. If you want to be able to play it a second time in a few months or years, and you’ve stripped away more than just the surface exudate, you may make the tape ‘dryer’ and more likely to show dry shedding. Alternatively, you might try something like a water-based cleaner with non-ionic surfactants (like Disc Doctor record cleaner) first – with very gentle wiping and a soft cloth – like a lens cleaner.
>
> Thanks for keeping me in the loop
> Eric Breitung
>
>
> From: Karl Fitzke [mailto:[log in to unmask]]
> Sent: Thursday, October 23, 2014 10:57 AM
> To: Steve Greene
> Cc: [log in to unmask]; Breitung, Eric; Ivan Keresztes
> Subject: Re: [ARSCLIST] Audio Cassette White Contaminant - Mass Spec Results! Stearic Acid
>
> Glad to do it, Steve. But Ivan gets the real thanks.
>
> I also want to note to everyone that you Steve, quite awhile ago noted this may be a "remnant of the lubricant". Peter Brothers had also noted to me earlier, that one of the possibilities he thought about after seeing the photos was a "fatty acid or stearate from the lubricant". Tom Fine mentioned "breakdown". Seva at soundcurrent mentioned leaching onto surface (not just edges). Malcolm Rockwell wondered about the possibility of "finger oils transferred when the tape was being inserted in the clamshells". Lots of interesting input, and I hope I've credited everyone here for these rather relevant ideas. Richard Hess as always provided encouragement and ideas.
>
> When I heard "stearic acid" from Ivan, I immediately thought of old discs and keeping fingerprints off them for fear of stearic and palmitic acid making fingerprints become unavoidably audible. Just seemed odd to be looking at cassettes and be talking about materials that perhaps threaten certain discs more (maybe only because cassette tape is not as easily touched).
>
> Regarding a solvent, yes, I'm very interested in what anyone has to say at this point. That list of solvents at the link in earlier email is perhaps a conversation starter?
>
> repeated again here...
>
> http://lxsrv7.oru.edu/~alang/onsc/solubility/allsolvents.php?solute=stearic%20acid<http://lxsrv7.oru.edu/%7Ealang/onsc/solubility/allsolvents.php?solute=stearic%20acid>
> (stearic acid solubility in various solvents, clean up clues)
>
> -Karl
> On 10/23/14 8:39 AM, Steve Greene wrote:
> Thanks for doing this important analysis. Hopefully this may suggest a solvent that can effectively take on the long-lost role of Freon TF, and Trichlor?
>
> Steve Greene
> Audiovisual Archivist
> Office of Presidential Libraries
> National Archives and Records Administration
> (301) 837-1772
>
> On Tue, Oct 21, 2014 at 2:31 PM, Karl Fitzke <[log in to unmask]<mailto:[log in to unmask]>> wrote:
> Hello again to everyone who has had some interest in this case. Thanks again for that interest.
>
> After having met with Cornell Plant Science Dept Mycologist, Kathie Hodge, who determined that our material was not mold, I got some encouragement from Eric Breitung at the LOC (thanks, Eric) which bolstered my own hopes of contacting the Cornell Chemistry Dept. We both believed there were good odds they could characterize our mystery material with a mass spectrometer. I was finally able to meet Michael Lenetsky there, and he in turn introduced me to Ivan Keresztes, who generously gave us some time and expertise with his mass spec (of which there are only a few hundred of in use in the US if I heard him right). Thanks very much to all of you in that chain of history. I hope I can return all the favors above somehow someday.
>
> Ivan determined that what we see on our tapes here is quite certainly Stearic Acid. My understanding is that this fatty acid is sometimes used as an audio tape lubricant dispersant. So it appears some of it simply exuded to the tape edges and surface (extreme environmental conditions? and/or poor formulation?). I mostly see it on the edges, but it does show up on the tape surface occasionally and sometimes exhibits a kind of crystalline growth pattern there. I'm just looking with the naked eye and a magnifying lens today, but I'll bring in a microscope to look more carefully tomorrow - maybe post more pictures where I've posted others (see below).
>
> Does anyone have alternative ideas about where this stuff came from and/or how it is used in tape manufacturing? Ivan wondered about the slip sheets maybe contributing, because they have this material on them too, and water wets to the sheet easier where the stearic acid is (perhaps because exudation took place at those spots?). I found that out when Ivan suggested I look for water solubility before coming over to see him. Didn't seem to work very well, and the mass spec results pretty much confirm that observation. The slip sheets also have a waxy feel to them, and Stearic Acid can be waxy.
>
> Stearic acid coming from Tape, Sheets, both?
>
> Now we figure out how to clean the tapes up anyway, and repackage in new shells.
>
> And by the way, we humans reportedly have Stearic Acid exuding from us all over. Ivan and I were very careful to not touch the tape and slip sheets with our bare fingers. He also did careful background measurements where we didn't see the white material and THEN looked for something new sticking out like a sore thumb as it did. I've posted a few pictures with the others posted earlier here: https://cornell.box.com/s/rafx7ue412ylu7svl0j6
>
> -Karl
>
> http://www.chemguide.co.uk/analysis/masspec/howitworks.html
>
> http://pubchem.ncbi.nlm.nih.gov//compound/stearic%20acid?r=chemical#section=Top<http://pubchem.ncbi.nlm.nih.gov/compound/stearic%20acid?r=chemical#section=Top>
>
> http://www.google.com/patents/US3993824 ("find" stearic)
>
> http://lxsrv7.oru.edu/~alang/onsc/solubility/allsolvents.php?solute=stearic%20acid<http://lxsrv7.oru.edu/%7Ealang/onsc/solubility/allsolvents.php?solute=stearic%20acid>
> (stearic acid solubility in various solvents, clean up clues)
>
> --
>
> Karl Fitzke
> Audio Engineer
> Macaulay Library
> Cornell Lab of Ornithology
> 159 Sapsucker Woods Road
> Ithaca, NY 14850
>
> 607-254-1100<tel:607-254-1100>
>
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>
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>
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> --
>
>
>
> Karl Fitzke
>
> Audio Engineer
>
> Macaulay Library
>
> Cornell Lab of Ornithology
>
> 159 Sapsucker Woods Road
>
> Ithaca, NY 14850
>
>
>
> 607-254-1100
>
>
>
> [log in to unmask]<mailto:[log in to unmask]>
>
>
>
> Our Mission:
>
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>
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H D Goldman Lagniappe Chemicals Ltd.
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