LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


ARSCLIST@LISTSERV.LOC.GOV


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  September 2017

ARSCLIST September 2017

Subject:

Re: Cassette repair question- a question of semantics concerning sticky shed?

From:

lists <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Fri, 1 Sep 2017 13:27:32 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (83 lines)

Pardon for the very late posting (have been massively busy with disaster
recovery projects) but the posting concerning "sticky shed" truly needs some
clarification as the way it is stated is very misleading.

Sticky shed is caused by binder hydrolysis.  This is indeed a function of
chemistry- but the chemistry involved is the interaction of water (often
absorbed from humid air) with the long-chain polymers in the tape resulting
in the polymers breaking down into short-chain, low-molecular-weight
oligomers.

While this is a chemical reaction, the reaction is very dependent on the
moisture content of the air in the environment in which the tapes are
stored.  The assertion that " they return to the sticky state eventually,
even in perfect storage" is not correct.  Should this happen, they have not
been placed in "perfect storage".  It has, in fact, been proven that
"sticky" tapes (without baking) will become less sticky if stored in stable,
low-RH environments.  If you store polyester-base tapes in an environment of
approximately 68 degrees and an RH of 20% or less, within a year, most (some
take longer) sticky tapes are no longer sticky and further testing 2, 3 and
5 years down the road, show that the tapes continue not to exhibit "sticky
shed".  As such, the "perfect storage" referred to in the earlier post is
not actually "perfect" storage for polyester-base magnetic tapes.

Another issue could be the method used for "baking" and how soon the tapes
are tested after they have been returned to storage.  Many people perform
short-term baking.  The issue with this is how hydrolysis affects the tape.
When hydrolysis occurs, polymers in the tape matrix as well as polymers on
the tape surface are effected.  The oligomer residue created inside the tape
matrix may partially migrate to the tape surface.  Heating the tape during
short-term baking primarily causes some of the oligomer residue to be
re-absorbed into the tape matrix leaving less on the surface and making the
tape, temporarily, playable.  It has little effect on the oligomers other
than their absorption into the tape and away from the surface.  As soon as
the tape begins to cool, these oligomers (slowly) start to migrate back to
the surface again.  This is one of the reasons that individuals who do
short-term baking state that you must play back the tape as soon after
baking as possible.  More sustained treatment (whether by "baking" or
exposure to very low RH environments or a vacuum) actually forces
cross-linking of the oligomer residue back into polymers.  As such, there is
no great abundance of oligomer residue to migrate back to the surface and
the tapes (so long as they are not exposed to elevated humidity) remain
playable for an extended time.

This is likely more information about the subject than most people really
want to know but to state that "sticky shed" is not a function of "storage"
is extremely misleading.

Just as background, I was one of the primary authors of the National and
International Standards about magnetic tape storage and magnetic tape
handling  published by ANSI, AES and the ISO.


Peter Brothers
SPECS BROS., LLC
973-777-5055
[log in to unmask]
Audio and video restoration and re-mastering since 1983


  

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Lou Judson
Sent: Thursday, June 29, 2017 11:44 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Cassette repair question

I believe it has been more or less proven that sticky shed is a function of
chemistry, not storage, as even after baking they return to the sticky state
eventually, even in perfect storage.

<L>
Lou Judson
Intuitive Audio
415-883-2689

On Jun 29, 2017, at 5:11 AM, Steve Greene <[log in to unmask]> wrote:

> But bear in mind, the loss of the felt suggests that the tape probably 
> wasn't stored in the best conditions, be concerned about sticky-shed, 
> or other binder problems in your future.

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager