[AV Media Matters] Back to Backcoat

[Jim Lindner <jim@vidipax.com>]

Peter Said:

In general, even though backcoat decay is a problem we encounter on
a daily basis, it is not a problem we have had particular
difficulties dealing with or correcting during restoration
processing.  It is possible that Jim Lindner's disenchantment with
backcoating resulted from a run in with a batch of the
aforementioned H-621.  It should also be noted that backcoat
shedding can and does contaminate the recording surface of adjacent
tape wraps.  This seems to be more of a problem on video than audio
tapes.

-------------
Yes, fair comment. We have run into many different types of backcoat
failure - some is pretty dramatic - and we can remove it fairly well,
but I am interested in trying to not repeat the "sins" of the past going
forward - and since there is a stock made that has no backcoat - the
obvious point is that it cannot have these specific problems. Having
said that - the obvious trade off becomes the loss of the nice things
that backcoat CAN do to maintain a nice pack.  What to do?

I also wanted to re-ask for comments on print-through that some of you
may not have seen because it was posted as one of my "moderators
comments" on the bottom of another post. The question I have relates
that the thickness of base stock and print through and coercivity....
The reason why most of us - myself included - have gone to 1.5 mil over
the years are primarily 2 reasons. Reason 1 is the issue of stretch and
general durability of a thicker stock - all other things being equal.
The other is the assumption that print through would be less with a
thicker stock.

I am questioning these assumptions with modern stock. #1 - I question
whether this assumption is really true any more - or if it is true
whether it is really relevant. The modern stocks appear to be much less
prone to stretch or other physical distortion - consider the super thin
stocks that we are now using.  So while 1.5 will be less prone to
stretching and other basefilm distortion then 1.0 - all other things
being equal - the question becomes how good is good enough... and with
modern tape transports for 1/4" for remastering which seem to be have
pretty good tape handling - is 1.5 REALLY that significant any more.

#2 - my understanding of the mechanism of print through is that it
occurs when high energy magnetic energy essentially cause a state change
 in areas of less energy (usually required by close proximity) -
increasing the distance between the areas of high and low energy
accomplishes the reduction of print through easily because of the
inverse square law - so even a .5 mil or less distance can cause a
dramatic reduction of the energy available. While I understand that for
low coercivity tapes this is a major issue and therefore the thicker
tape makes perfect sense, it seems to me that modern tape of high
coercivity would not really have the problem in the first place because
the energy would have to be so high to overcome the high coercivity of
the tape even in the low energy area, as to make the printthrough a
non-issue. Now one issue is that higher coercivity takes higher
recording energy to make a recording, but once recorded that higher
energy is no longer "present" and one would have to have the high energy
to overcome the coercivity in the low energy (quiet) areas, which is
simply not available.

So IF that is true - and I may be TOTALLY WRONG on this - is there in
fact any REAL reason (NOT past practice) with modern tapes and modern
transports not to use a 1.0 mil tape stock?

I would particularly like to hear from some of the vendors who I know
lurk on the list to hear where or if I have gone wrong on all this.

Thanks to all
jim

Jim Lindner - President
VidiPax - The Magnetic Media and Information Migration Full Services
Company
Telephone 212-563-1999
www.vidipax.com
Moderator of A/V Media Matters@topica.com