A few last comments based on these and Richards follow up. I
firmly think that tapes in fact DO need individual treatment - but one CAN
design a system that will allow that process to be done and still process a
large quantity of materials with very high quality control. That is what VidiPax
is all about. I do reiterate that Pelon is ONE treatment technique that we use,
there are others. I am sort of surprised that people are reacting like this is a
"new" idea here. Sorry but it isn't. Pelon has been used in tape
manufacture for this purpose for a LONG time. Some commercial tape
cleaners Like the Elicon and the machines still made by RTI all use Pelon wiper
systems. WE have used it for almost 10 years now and we have processed Hundreds
of thousands of tapes (at some point you sort of stop counting - you know -
billions of burgers sold at micky D's...
Now exactly HOW you use the
material, the way you move the tape, the contact, tension and a bunch more
variables are VERY important -
So the secret is in the sauce - it took me
2 years to figure it out when I started the company!
Richards comments
about RF. I was talking about audio and video - and indeed I think of RF as
signal strength - which in a carrier based system is what it is - I did not want
to go into too many details - but I WAS referring to audio as well. At
some point I can go into the magnetics of all this. But for the moment consider
a few things. There are many different aspects in tape construction that will
effect the signal output as well as the signal to noise ratio. In this specific
case we are going to concentrate on S/N and what impact (if any) is there in
removing lose surface particulate. First consider that the particles that we are
removing are not necessarily magnetized as part of the recording in the first
place. Not all particles orient themselves. These "background" particles are a
significant proportion of the particles on the tape. Also consider the
coercivity/retentivity hysterisis curves and think that these particles may not
necessarily be the ones that were oriented correctly in the first place. They
are not necessarily the nicely elongated particles, nor are they necessarily the
ones with high energy orientation. Consider the track width relative to these
particles - their more or less random distribution along the tape (meaning that
there is not necessarily more particles removed over a LOUD section of a
recording as opposed to a quiet section). And so forth. Also consider the impact
of a lose particle in the WRONG place - which is quite possible too - which will
actually reduce signal to noise. And consider the absence of magnetized
particles is no noise but silence. Stir this around in your mind - and where I
think you will come out is that removing the particulate is far better then
leaving it.
One final note. In the rare cases where we do bake..... yes -
we do clean with Pelon after as well. While baking may make tapes less sticky -
it does not deal with particulate contamination and it still is an issue even if
a tape IS baked.
And finally for those magnetic geeks in the audience -
the proper explanation that I did not want to get into of the above
is....
C. Mee and E. Daniel, Magnetic Recording, Volume III, McGraw Hill,
1988, pp 155-170.
And amazingly some of it is on the web at:
http://www.ee.washington.edu/conselec/CE/kuhn/magtape/95x1.htm
which
is an excellent article - specifically consider:
Noise
sources[18]
Bulk-erase noise: There is a noise source due to the size and orientation of the particles in the magnetic coating. The signal to noise ratio for a band of wavenumbers from k to dk (k = 2/) is given by:
Thus, the signal to noise is proportional to the track width (w), the volume fraction of the coating occupied by particles (p such that the maximum = 1) and the orientation (F(theta) = 3/8 for random and 1 for perfect). The signal to noise ratio is inversely proportional to the mean size of the particle (s) and the standard deviation of the particle size distribution sigma. Therefore, decreasing the track size, increasing the number of particles, and decreasing the particle size; will improve the bulk signal to noise.
In our specific case we are decreasing the
number the particles by a VERY small amount in porportion to the volume in the
coating. Since the particle size distribution is the same in aggregate - the
impact of what we do is essentially nothing from a signal to noise ratio
perspective - and in actual field experience it actually seems to improve s/n
because of improvement of head performance which is a VERY important factor. The
gap remains clean, s/n is better - output is better for low and high energy
signal strength..... you get the idea.
James
Lindner
General Manager VidiPax Division
VidiPax - The Magnetic Media
Restoration Company
Executive Vice-President
Loudeye
Technologies
NASDAQ Symbol:LOUD
VidiPax
450 West 31 Street
New
York, N.Y. 10001
212-563-1999 ext.
102
www.vidipax.com
Moderator: AV Media Matters Listserve
To
subscribe to AV Media Matters Listserve send an email
to:
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> -----Original
Message-----
> From: owner-ARSCLIST@xxxxxxxxxxxxxxxxx
> [mailto:owner-ARSCLIST@xxxxxxxxxxxxxxxxx]On
Behalf Of Joe Salerno
> Sent: Saturday, May 12, 2001 10:10 AM
> To:
ARSCLIST@xxxxxxxxxxxxxxxx
> Subject: Re: arsclist Pellon and thoughts on
baking/Philosophy
>
>
> Considering the limitations of either
pellon or baking tapes. I agree that
> the migration must take place but I
would not abandon the
> original artifacts
> until they become
completely unusable. Assume that in the near
> future pellon
> was
proven conclusively to be superior (minimal or no damage to originals
>
and successful retrieval) to tape baking by some small margin. If it is
as
> time and labor intensive process as it seems, would not baking "win"
the
> contest on virtue of limited archival funding? Tapes can be "batch
baked"
> (I've invented a new term) whereas the pellon process would
seem
> to require
> individual attention to each
roll.
>
> Joe Salerno
> Video Works! Is it working for
you?
> PO Box 273405 - Houston TX 77277-3405
> http://joe.salerno.com
>
joe@xxxxxxxxxxx
> Fax: 603-415-7616
> ----- Original Message
-----
> From: "Richard L. Hess" <lists@xxxxxxxxxxxxxxx>
> To:
"Sarah Stauderman" <StaudermanS@xxxxxx>
> Cc:
<ARSCLIST@xxxxxxxxxxxxxxxx>; <harry_rice@xxxxxxxxx>
> Sent:
Friday, May 11, 2001 4:30 PM
> Subject: Re: arsclist Pellon and thoughts
on baking/Philosophy
>
>
> > I wonder if the baking process
is any worse than the tape sitting in an
> > aluminum shipping
container on the tarmac at LAX in the summer
> waiting to
> > be
loaded on the Fed Ex plane--we all are guilty of shipping our master
>
> tapes by Fed Ex and worse without temperature controls.
>
>
> > I have heard one horror story of baking--but only one.
>
>
> > While I am all in favor of doing no harm to original
artifacts
> we also get
> > to the question of whether the
artifact or the content is the important
> > item. Most of the people
I'm working with -- and granted they're not the
> > Smithsonian -- want
the content and could care less about the carrier.
> They
> >
want the content to sound absolutely as good as it can. Several people
>
have
> > come to me after horrid transfers and have said can you do
anything? I
> > agree with Mr. Lindner: go to an expert first not after
you've made the
> > problem worse.
> >
> > I have
seen sticky-shed so bad that a reel would not
> self-unroll. Many
of
> > the tapes with sticky-shed will leave stuff on the guides,
but
> will unroll
> > easily. Some will pull so hard you fear the
oxide will be left
> > behind...almost like Scotch 111 removable
mending tape being pulled off
> the
> > roll.
>
>
> > What weight Pellon do you suggest? I'd like to try it, but I
won't on a
> > tape I have to restore--if what I see on tape guides is
any indication
> > there will be a lot more on the Pellon if it's going
to remove all the
> > debris that is likely to cause
stickiness.
> >
> > Besides, the Pellon treatment isn't tested
in any scientific
> way, either.
> > It's another process that
has been evaluated by empirical test and while
> > Ms. Stauderman and
Mr. Lindner (both of whom I have great respect for)
> > worry
about the baking process, I'll stand out here as one
> voice
worrying
> > about removing enough material to make the tape
non-shedding by a wiping
> > process. I know in previous emails Mr.
Lindner has said the amount of
> > material removed is infinitesimal,
from what I've seen on SOME tapes and
> > what comes off on the
polished guides when I have to wind the
> tape before
> > baking
(which I hate to do) I would be amazed that there wouldn't be a
>
huge
> > amount of oxide on the Pellon.
> >
> > What
I do know is that prior to baking, the tape's oxide
> surface seems
to
> > be soft and tacky. After baking it is hard and shiny just like
new tape.
> >
> > Once long ago I did well in the Chemistry
Achievement Tests but never
> > pursued it further so you can take this
with a grain of salt, but what I
> > think I'm seeing in the
sticky-shed tapes appears almost to be a state
> > change from solid to
goo (conceptually, think of ice to slush). From my
> > observations it
doesn't appear to happen to the surface only, but rather
> it
> >
appears to be deep within the binder/oxide paste that is placed on the
>
base
> > film.
> >
> > I don't have any bad
sticky-shed tapes at the moment, but I
> will look for
> >
one--or maybe try to make one. Do you think if I leave a reel of 1981
>
> vintage 456 in my bathroom for a month of showers it will be
hydrolized
> > enough? I live in LA--I have to do something dramatic to
match
> the climate
> > of the Pacific Northwest where my worst
sticky-shed examples came from
> (and
> > have been
returned).
> >
> > I think we perhaps come from two different
worlds. Hopefully, at the
> > Smithsonian (and most of VidiPax's other
clients) material is
> stored in at
> > least office environments
and often special-purpose archival storage
> > facilities. Contrast
this to 456 kept in a wooden barn on a small island
> > off the coast
of Vancouver Island. Trees hanging over the barn.
> No central
>
> heating only space heaters in some rooms. I've heard of other tapes
kept
> > against a stone basement wall in lake country. This is the
fate of many
> > masters for LPs that were made in the 70's and 80's
(if they didn't find
> > their way into the dumpster). The ones from
the small island had
> > collectively sold probably 120,000 copies--not
huge but respectable. We
> > want to do a retrospective CD set.
>
>
> > Anyway, I spoke at length with Mr. Lindner at the NAB and
we're
> in violent
> > agreement that studies should be done to
see what the problems are. I
> don't
> > have a citation, but the
1dB loss at high frequencies due to baking was
> > from an Australian
study as I understand it.
> >
> > I'm not even sure how you do
the test to attribute the losses to the
> > baking. Couldn't the losses
be attributable to the hydrolization? For
> > example if a hydrolized
tape that has been baked loses 1dB at 20kHz
> > compared to a
non-hydrolized tape that wasn't baked how would
> you know if
> >
it was the baking or the hydrolization. We would know if baking a
> >
non-hydrolized tape yields the same loss, but it's not conclusive
>
otherwise.
> >
> >
> > <soapbox mode
on>
> > The following is not really addressed to anyone in
particular but to all
> of
> > us in general.
>
>
> > Now let's move on to acidosis or vinegar syndrome (VS) to make
a point.
> The
> > Kodak Molecular Sieve material is reported to
retard deterioration from
> VS.
> > Some 1940's vintage
BASF/Agfa/IG Farben Magnetophonband and Scotch 111
> that
> > I
recently transferred suffered from a vinegar smell but still played
>
well.
> > But for how much longer? How does VS affect tape? What
is the timetable
> > compared to film? What can slow it? At SOME
POINT we will need to make
> the
> > decision to copy the
material and abandon the current carrier. We've had
> to
> > do
that with nitrate based film stock. At some point we'll have to make
>
> that decision with audiotapes. It seems that we may have abandoned
>
> newsprint too soon in favor of microfilm and I know that archivists
and
> > librarians are smarting from that one and are being called to
task for
> that
> > decision, but let's make sure we don't lose
assets by inaction.
> Let's get
> > material transferred to a
reasonable format before it's too
> late. Inaction
> > may solve
some of the problems for us.
> >
> > We have funding,
staffing, and technological challenges to
> overcome but we
> >
have to make a concerted effort to decide how to save this
> material
before
> > it's too late. When will it be too late? I can't say.
Tomorrow won't
> > be...20 years might be for some material.
>
>
> > One estimate is that there is 50M hours of material in the
world to
> > transfer (yup- fifty million). Some think that's
conservative. Assuming
> 4:1
> > time for transferring (and let's
not even say "to what") that's 200
> million
> > person hours or
100 thousand person years of transferring.
> >
> > <soapbox
mode off>
> >
> > Cheers,
> >
> >
Richard
> >
> >
> > At 04:13 PM 05/11/2001 -0400,
Sarah Stauderman wrote:
> > >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,
> > >
> > >Sarah
Stauderman
> > >
> > >Sarah Stauderman
> >
>Preservation Manager
> > >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
> >
>costs.
> > >
> > >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!
> >
>
> > >Cheers,
> > >
> > >Richard
>
> >
> > >
> > >At 10:54 AM 05/11/2001 -0400,
harry_rice@xxxxxxxxx wrote:
> > > >Richard:
> > >
>
> > > >What are Pellon wipes?
> > > >
>
> > >Harry Rice
> > > >Berea College
> >
>
>
>_________________________________________________________________________
>
> > ______
> > > >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
> > > > >worst.
> > > >
>
> > > > >Good luck finding someone to do it!
> >
> > >
> > > > >Cheers,
> > > >
>
> > > > >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
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> > > >http://www.arsc-audio.org/arsclist.html
>
> > >Copyright of individual posting is owned by the author of the
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> and
> > > >permission to re-transmit or publish a
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> > > >from the author of the post.
>
> > >
> > > >
> > > >
> >
>
> > >-
> > >For subscription instructions, see the
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> > >http://www.arsc-audio.org/arsclist.html
>
> >Copyright of individual posting is owned by the author of the
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> > >permission to re-transmit or publish a post must be
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> > >from the author of the post.
> >
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> > For subscription instructions, see the ARSC home page
>
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>
> Copyright of individual posting is owned by the author of the
>
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secured
> > from the author of the post.
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>
>
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Copyright of individual posting is owned by the author of the posting
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