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Re: arsclist Pellon and thoughts on baking
To clarify about Pellon: it is non-woven polyester (fabric), also known as polyester web.
One issue that it seems to me is always avoided in discussions about baking is that it has never been tested in a scientific laboratory set up to compare and analyze the effects of baking. There's lots of anecdotal evidence that says that baking is ok and that it works (there's a patent on it, in fact).
But, speaking as a conservator, it is simply wrong to use untested treatments on cultural artifacts. At the very least, audio engineers who use baking need to understand what the long-term effects of baking may be, or explain thoroughly to clients/cultural institutions that baking may result in irrevocable damage to the original artifact. Perhaps baking is the only method to use on tapes with heavy sticky-shed resulting from hydrolysis. If this is the case, we still need documented evidence of its efficacy and implications.
Meanwhile, I participated in a study of cleaning videotapes (3/4" u-matic was the format, and the brand was Ampex, and BASF) using non-woven polyester. This report was given at the American Institute for Conservation annual meeting in June 1999. The scientist, Mary Baker, examined the surfaces of tapes using FTIR. There was no chemical change before and after cleaning. Unfortunately, the tape sample was too small and the means to study a change in picture quality was not available. We also did not get the enormous amount of residue on the cleaning webbing that Mr. Hess has observed. In the end, we felt that no chemical change was a good indicator of the utility of cleaning with polyester webbing, but that it warranted additional study.
Incidentally, this study was carried out at the Smithsonian Center for Materials Research and Education, which is slated to be eliminated from the Smithsonian in December 2001. The cleaning, I should also mention, was carried out at VidiPax's New York lab. I wish that there was a concerted effort to characterize treatment activities and their implications by audio restorers and video restorers. Groups like ARSC and AMIA need to work with SMPTE and standards organizations to do this research. If I had a lab, I would.
Opposed to baking until it's proven otherwise, or as a very last resort, I remain, wishing you all best luck with your materials,
Smithsonian Institution Archives
202-357-1421 x 56
>>> lists@xxxxxxxxxxxxxxx 05/11/01 12:20PM >>>
pellon (a thin stiff white fabric found in craft and fabric stores) (as
found on the Web)...
To be totally fair, Jim Lindner is a much more experienced person than I in
dealing with tape problems, although I'll confess to being resourceful and
obtaining good results. We philosophically disagree on the superiority of
the two processes:
Lindner is horrified at the thought of baking. He tries to avoid it at all
I, on the other hand, am greatly concerned about wiping tapes until all the
goo is off because I see the stuff on the wipes as containing oxide in
now-scrambled orientations that used to contain the signal I'm trying to
get off the tape.
In one double-blind test, Lindner found that about 60% of the listeners
(not much above the 50% random chance) (if I correctly recall his telling
me on the noisy floor of the recent NAB show) found some deficiencies in
the low frequencies of baked tapes as compared with wiped tapes. Now, I
don't know how you can do double-blind tests of this with precisely the
same material without copying and the copying process itself (especially at
15 and even more so at 30 ips) introduces substantial low frequency
anomalies due to "head bump" phenomena. So I am not sure if Lindner's
reported double blind test is hearing the restoration process or some
anomaly in the copying process.
As to baking, there have been some reports of a 1dB loss of the highest
frequencies. I have baked one set of tapes twice and on the second baking
reproduced them on a superior machine as opposed to the one after the first
baking. The tapes sounded better after the second baking on the superior
machine, so the machine difference is more than the difference in
baking--an IMPORTANT point to remember.
My comparison of machines was between a ReVox A77 and a Sony APR5003V. In
my mind, the APR is one of the five best machines ever made, the others
being the Studer A820, the Ampex ATR-100, the Ampex MR-70 (if you want
tube), and the Nagra T. The ReVox A77 was a competent low-end machine that
worked as well as many other machines in its price range. If you've got
high-end tapes, they deserved to be digitized from a high-end machine.
More than you asked...but it's all related!
At 10:54 AM 05/11/2001 -0400, harry_rice@xxxxxxxxx wrote:
>What are Pellon wipes?
>Subject: Fwd: BOUNCE arsclist@xxxxxxxxxxxxxxxxx: Non-member sub
>From: <ARSCLIST@xxxxxxxxxxxxxxxx> at berlink
>Date: 5/11/2001 9:20 AM
> >Date: Thu, 10 May 2001 12:36:56 -0700
> >To: Language Laboratories and Archives <language-labs@xxxxxxxxxxxx>
> >From: "Richard L. Hess" <richard@xxxxxxxxxxxxxxx>
> >Subject: Re: arsclist sticky shed
> >Cc: ARSCLIST@xxxxxxxxxxxxxxxx
> >Hi, Barbara,
> >There are resources on my Web page at http://www.richardhess.com/tape/
> >I think at least some of these people deal with sticky shed syndrome.
> >VidiPax does it by wiping with Pellon wipes, most of the rest of us bake.
> >I've had good results with a whole heap'o'tapes but it's never guaranteed
> >and while we all take the utmost care we cannot be held liable for loss of
> >the master--I think that's pretty standard.
> >If it's only one reel I could look at it for you. If it's much more than
> >that, I don't have the time. $100 hour is close to the going rate (I think
> >VidiPax charges $95). That's per hour of studio time not per running hour
> >of program. My general estimate is that it takes from 4-10x depending on
> >what needs to be done and how good you want it. The 6x is typically
> >finessing individual dropouts--you've got to find them which means
> >listening and watching.
> >What is the tape format, what is the tape brand, how long is it? What's on
> >it? what do you want to do with the content?
> >I see you're from the language labs. If it's just word and it's a
> >continuous tape (no splices) it might not even take 4x. If it is music with
> >lots of splices for CD re-release, It generally approaches the 10x figure.
> >I've done reel tapes as early as 1947 with some Bing Crosby excerpts on
> >them (no sticky shed, but lots of problems) but most of my current work is
> >centered on folk music from the 70's and 80's when sticky-shed was at its
> >Good luck finding someone to do it!
> >Richardy copying process itself (especially
> >At 01:12 PM 05/10/2001 -0500, Language Laboratories and Archives wrote:
> > >Hi, We just had a case of sticky shed, and the company we dealt with many
> > >years ago is no longer in business. Who are you all working with?
> > >
> > >Barbara Need
> > >UChicago--Language Labs
> > >-
> > >For subscription instructions, see the ARSC home page
> > >http://www.arsc-audio.org/arsclist.html
> > >Copyright of individual posting is owned by the author of the posting and
> > >permission to re-transmit or publish a post must be secured
> > >from the author of the post.
>For subscription instructions, see the ARSC home page
>Copyright of individual posting is owned by the author of the posting and
>permission to re-transmit or publish a post must be secured
>from the author of the post.
For subscription instructions, see the ARSC home page
Copyright of individual posting is owned by the author of the posting and
permission to re-transmit or publish a post must be secured
from the author of the post.