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(From page 30)
Three factors
affect the breakdown of tape binders:
- Humidity
(above RH 40%);
- Temperature
(ideal storage 65 );
- Frequency
of use.
Studios in humid climates (like Florida, New Orleans, etc.)
can see tape shedding problems as early as one year. But
efforts to control elimination of hydrolysis, even if you keep
your tapes in a temperature and humidity controlled environment,
exposure to higher than 40% relative humidity for just one
day will trigger irreversible hydrolysis which spreads, according
to one tape manufacturer's engineer "like a cancer through
the entire tape pack". Attempts to seal the reel in plastic
only traps existing humidity within the reel and can accelerate
this tape binder breakdown. Ampex senior product support
engineer, Jay Zacharias, suggests sealing reels in plastic with
a package of silica gel to remove existing moisture. Jay
further suggests fast forwarding and rewinding all stored reels
once a year to "air them out". He also notes that
customers that use the same reels over and over (like radio production
users) seem to experience no hydrolysis problems. The more
you use your reels the better.
The three main symptoms of hydrolysis are: (in progressive
severity)
1. Higher than normal static discharge on winding. Static
discharges are actually high voltage, low current spot erasures.
(Scenario #1)
2. Audible squealing as tape "stutter-sticks" across
tape machine heads and guides. Oxide starts to shed. (Scenario
#2)
3. Finally, the tape machine downright refuses to play the tape.
Severe oxide shed occurs during futile attempts to play the tape.
Also digital tape users beware: Even though digital tape's
higher metal particle content make it less prone to hydrolysis,
it can and will still happen. And ADAT's S-VHS tapes
are formulated with standardized oxides and will likely experience
shedding problems too.
Next month: How to recover hydrolyzed tapes. See you then!
Tape
Shedding - Part Two
©
Mike Konopka
Last month I discussed symptoms and causes of tape hydrolysis
or "shedding" which can range in severity from static
discharge spot erasures, to thick oxide gobs which prevents your
tape transport from even operating. This month we'll find
out how these hydrolyzed tapes can be recovered.(continued)
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