[ARSCLIST] Hydrolysis and the baking of tapes

[Jacqueline von Arb <jacqueline.vonarb@xxxxxx>]

Dear bakers,

I'd like to reiterate the usefulness of the IASA publication that Richard
Green advocated a short while ago: "Guidelines on the Production and
Preservation of Digital Audio Objects" - it has a few tidbits on baking as
well!

Top technical experts contributed their knowledge, the content was reviewed
by the IASA Technical Committe and the booklet is recommended by UNESCO as
best practice for Audio-visual Archives. Thanks to the editor, Kevin
Bradley of the National Library of Australia, the content is penned in a
language accessible to all levels of sound nuts, from the archive managers
to the "techos". Refreshingly free of technical condescension, it is an
essential tool on the road to revive sound dinosaurs on to a digital
medium. See the contributors and the introduction at:
http://www.iasa-web.org/tc04/tc04.htm

Chapter 5 of the Guidelines is about Signal Extraction from Originals, 5.4
deals with the Reproduction of Analogue Magnetic Tapes and 5.4.3.2-9 in
particular addresses Hydrolysis (Sticky Shed Syndrome) and various
approaches of treatment.

Referring shortly (and far from comprehensively) from that section: the
common approach called "baking" ought to occur in a chamber at a very
'stable temperature approaching 50 C [122 F] and 0% RH [relative humidity]
for period of around 8-12 hours'.

However, one should shy away from domestic ovens, as those have poor
temperature control; the digital display (if you have one...) may indicate
a mean temperature of 50 degrees, but the thermostat may in effect cause a
sway in temperature where both the preset high (that makes the thermostat
turn off the heat source) and the constant cycling of temperature may be
detrimental, if not cause damage. A laboratory oven provides a much more
stable temperature control.

Another tip (also in the guidelines) for reducing the level of print
activity activated by the temperature increase is to interleave with new
tape.

May the result of your baking be aurally palatable!

 Soundfully yours, Jacqueline von Arb
Norwegian Institute of Recorded Sound