Re: [AV Media Matters] Video Tape Recycling Rejuvination

[ian_gilmour@screensound.gov.au]

In many collections of tapes with varying ages and storage history, it is
common to find examples which are decomposing or contaminated, which will
suffer further damage if they are simply run through a cleaning/checking
machine without a thorough examination and treatment as necessary. For
instance, is there any mould or dirt on the edge of the pack which will
contaminate the playing surface if not removed first? Does the tape unwind
and spool without layers sticking together or peeling off?

So, assuming the first 99 steps are all taken care of ...............
The surface checking on the newer RTI machines such as the 4100 [Betacam
family] and 5100 [DV family] use optical sensors for a very basic
measurement of reflectivity as well as for tears. They can pick up larger
creases, kinks and the like, but they won't tell you about the magnetic
properties. Remember that the wavelength recorded on most recent video
formats is less than one thousandth of a millimetre. You can perform a more
comprehensive magnetic check on some of the RTI machines by erasing the
original content and recording a test signal, but I'm guessing that you
don't want to literally erase and recycle your archival tapes. It is not a
good idea to have machines for erasing tapes in archives without some
pretty good safeguards [procedural as well as mechanical/electronic]. We
also discourage folks from using 2nd-hand tapes for any serious
preservation.

To check the previously recorded signal thoroughly, you need to measure the
rf level on an analogue or digital video playback machine, or measure bit
errors or conduct higher levels of data analysis on digital formats. The
built-in error flags on some models only indicate severe signal loss.

The other function of the RTI machines is cleaning, which is done in two
ways:
1. Tissue wipes and a suction head which work best with dry deposits like
dust;
2. A sharp sapphire wedge which scrapes off some of the surface debris, and
may remove sticky deposits. The trick is to keep the scraper clean and
prevent redeposition of contaminants. Scrapers can also scratch or remove
magnetic coatings which have decomposed, so you may wish to check the
surface condition first. I personally have reservations about running
fragile tapes at over 50 times normal play speed over sharp edges, although
tapes in good condition with slight contamination will normally benefit
from careful cleaning. Despite all the caveats, however, there aren't too
many other options when it comes to video tape cleaning and checking.
Whatever your choice, success will depend on having an experienced
operator.

Ian Gilmour
Engineering & Research Group
ScreenSound Australia
- the National Screen and Sound Archive
www.screensound.gov.au

Jodie Foley <oralhistory@mcn.net> on 06/12/2000 09:57:13

Please respond to AV-Media-Matters@topica.com

To:   AV Media Matters <AV-Media-Matters@topica.com>
cc:
Subject:  [AV Media Matters] Video Tape Recycling Rejuvination

Hello list servers:

Quick question--is any one out there using the RTI  Tape
Recycling/Rejuvenation system for archival preservation of video  tapes?
How is it working?  Any problems with  drop-out?

Please let me know, we are considering  purchasing a system and would like
to have opinions other than the  salesman.

Thanks,
Jodie Foley
Montana Historical Society Archives
oralhistory@mcn.net