Date:Fri, 7 Nov 2008 13:00:49 -0500
Reply-To:Association for Recorded Sound Discussion List
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From:"Charles A. Richardson" <[log in to unmask]>
Subject:Re: revisiting tape bakers
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There has been a continuing discussion of baking as a remedy for
sticky shed contamination on magnetic tapes. List members point to
the Ampex Baking Patent as authority for baking sticky shed tapes to
enable playback. The discussion seems to assume the safety or ignore
the damage that baking does to tapes. Baking is dangerous and much of
the information about baking tapes is misleading. The following is
not just my opinion or assertion but has been substantiated by the
scientific analysis of a nationally recognized, independent forensic
1) The baking process set out in the Ampex Patent melts the sticky
shed debris with heat energy. This stops tape
frictional squealing while the sticky shed debris remains in a
liquefied state, but the squealing returns after the debris cools off
and solidifies once more. It does not cure the underlying chemical
causes of the tape problems which return endlessly.
2) Magnetic tapes are made with complex chains of polymers. The
polymer links are extremely heat sensitive. Baking destroys the
flexibility of the tape and the binder adhesion because it damages the
links in the chemical chains. Applying heat permanently breaks down
the chain links, causes unwanted new cross linking of chemical bond
links, and creates new, unwanted chemical compounds. The tape becomes
increasingly brittle and the coatings start to flake off the base
film. Repetitive baking increases the damage to the chemical,
magnetic and physical components, and eventually destroys the tape.
3) Sticky shed debris, liquefied by baking, collects at the tape head
gap. This debris accumulation pushes the tape oxide surface further
and further away from the tape head's surface at the critically
important head gap. This collection of debris causes a physical and
major magnetic separation loss, which, as you know, severely reduces
the ability of the tape head gap to magnetically scan the short wave
lengths of the oxide's recorded content at high frequencies. This
results in inferior mechanical, magnetic and sonic playback
performance and thereby a deficient transfer of tape content. The
playback head's high frequencies are greatly reduced, the noise
reduction system playback performance mis-tracks, and worsens these
high frequency losses. Thus the tape sound quality is now made dull
and lifeless because sticky shed debris on the head gap magnetically
attenuates proper and complete scanning of the important high
frequencies that are now greatly reduced or even missing altogether.
4) Baking causes increased print-through.
5) Baking causes weakened magnetic fields and thus lower flux and
output signal levels.
6) Baking does not provide any "restoration" or "rejuvenation" of
binder chemicals. To the contrary, it causes progressive
and permanent damage to and destruction of the tape. A fundamental
thermal law of chemistry is that heat energy destroys
7) Baking is not a safely repeatable solution. Each time a tape is
baked, it requires higher temperatures and/or longer bake times. Each
round of baking produces worse chemical, physical, magnetic,
mechanical, and sonic results.
8) The high heat used in baking drives off by evaporation the light
weight polymers and causes the magnetic particle material attached to
them to fall off.
9) Baking the tape damages the tape's magnetic content and seriously
degrades the playback performance. People have ruined tapes by baking
them, but this is generally not admitted, possibly because of fear of
liability and potential loss of income. They may be unaware of any
other method to stop tape squealing safely and permanently.
10) Some proponents of baking try to rationalize this dangerous
baking method by inventing a new set of terminology and
circumstances, such as "soft binder syndrome", to justify using the
baking technique to obtain a mediocre playback. I am unaware of any
scientific evidence or support by an independent laboratory for "soft
binder syndrome" as either being separate and distinct from or a sub-
set of sticky shed syndrome.
11) The accurate standardized chemical terminology is that tape
binders are inherently hygroscopic, and thus are susceptible to
hydrolysis. The only safe and highly effective method to restore and
preserve tapes suffering from hydrolysis of the binders, or sticky
shed syndrome, is to first, put the affected tapes in a stable
environment of low heat and humidity for as long as it takes to
reverse the hydrolysis reaction, and then second, safely clean all
the tape's debris from both the oxide surface without damaging the
surface, and also completely remove its chemical material causal
source, namely the deteriorated carbon black back coating.
12) Much reliance has been placed, or should I say misplaced, on the
Ampex Baking Patent. The Ampex Baking Patent is intended solely to
expedite the transfer of recorded information. The title, "Restored
magnetic recording media and method of producing same", is inaccurate
because the baking method does not take steps to preserve the media,
but only to restore temporarily a "playable condition" in the media.
It is merely a band aide fix, not a cure.
13) The 1993 Ampex Baking Patent suggests that heating tapes to
120-130 degrees Fahrenheit "does not further deteriorate the tapes"
and implies that baking a tape for prolonged periods of time is safe.
The patent does not cite scientific or chemical evidence to back the
"no further deterioration claim". Moreover, the claim runs directly
contrary to pre-existing chemical thermal laws and 1980 scientific
findings that heat damages tape's magnetic content by increasing print
through levels, published in a scholarly article written by Ampex's
own staff scientist, H. Neal Bertram. "The Print Through
Phenomenon" (JAES Volume 28, Issue 10, pp.690-705; October 1980).
14) The elevated temperatures stated in the Ampex Baking Patent,
120-130 degrees, also violates Ampex's own tape manufacture's warranty
limiting heat to not exceed 90 degrees. This chemically abusive high
baking heat radically shortens tape lifespan to a small fraction of
the time tapes can last if they are instead stored and handled as
chemical science requires. Tapes have the ability to be reliably
archival for a very long time. However, if abused by improper
storage, handling, and wrong headed restoration, then tapes are
damaged, degraded, and destroyed far ahead of their time.
15) As you know, a patent does not confer a certification or
implication that an invention is scientifically proven to be effective
or safe. A patent is a grant from the U. S. government (or other
authority in other countries) of a right to exclude others from
making, using, or selling one's invention and also includes the right
to license others to make, use or sell it.
A patent application is only narrowly and formally reviewed to
determine whether the invention is entitled to be granted a patent
under U. S. Patent law. The most important requirement under U. S.
Patent law is that the invention be a new or useful process, machine,
manufacture, or composition of matter, or any new and useful
improvement thereof. Clearly, a patent, baking or otherwise, is no
scientific authority and no certification of safety.
16) Richardson Magnetic Tape Restoration is concerned, not just with
minimal baking type partial recovery of the magnetic content
information contained within a sticky tape, but with the long term
preservation of magnetic tapes as the primary or original source of
the all the magnetic content information on the tapes and to create
optimal playback conditions for high quality reproduction needs. To
achieve this goal, RMTR hired a nationally recognized independent
forensic chemical laboratory to test chemically and to examine under a
high power electron microscope, the sticky shed tapes, before and
after application of baking heat treatments. The lab results showed
significant deterioration of the tape after it was heated as per the
Ampex baking patent. Application of heat treatments, the chemists
concluded, accelerates even more damage from hydrolysis, and increases
the cross linking of the polymers used in making the PET Mylar base
film and binder components of the tapes. This baking practice soon
"leads to unwanted tape destruction." The chemists also concluded
that the new RMTR process was both safe and effective for tape
restoration, preservation, and playback mastering needs.
I have a written paper that elaborates on these concepts. The paper
is available on request.
If you or any other list members have independent chemical laboratory
research that refutes these points or supports baking as both safe and
effective for the restoration and preservation of magnetic tapes, I
would appreciate seeing it.
Charles A. Richardson, RMTR LLC
On Sep 27, 2008, at 8:42 PM, Richard L. Hess wrote:
> At 08:05 PM 2008-09-27, Tom Fine wrote:
>> I forgot if Richard has a complete list of must-bake types on his
>> website. If so, I'm sure he'll provide a link.
> I do and your points that I snipped are important for those who
> haven't heard them before.
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
> Detailed contact information: http://www.richardhess.com/tape/contact.htm
> Quality tape transfers -- even from hard-to-play tapes.