RE: [AV Media Matters] Recovery of AV media in flood disaster

[rohre@arlut.utexas.edu]

Ah, a new topic.

Water damaged tape:  (and some of this would apply to film)

First of all, until the media can be transported to a conservation
lab, you must keep it submerged. Of course, in case of flood waters
receding, at least put it back in a container of distilled water.

When we had a sea water damaged tape from a subsurface buoy
recorder, we kept it in seawater, and at same temperature as the
depth at which it flooded as well as we could.  IE, keep it cool to
cold.

The process then was to rinse multiple times with distilled water,
until any mud, sediment, etc. is removed.  For tape, this is done
with the item still on the original reel.  Then, it is slowly
unspooled to a clean metal reel with the side windows.  In the case
of chemicals and salts in the contaminated water, you might already
have corrosion forming on metal reels, and thus this rereeling helps
prevent metal salts from coating the tape.

While it is rereeling, you can remove the heads from the rereeling
machine, and install pad wipers or even hold a pad against both
sides of the tape, moist with distilled water to further remove
salts.  You should use minimum pad pressure against the oxide and
backing. ( This step might not be advisable for film, perhaps movie
film experts will advise.)

When the tape is gently rewound on a new reel, you should put it in
a vacuum chamber while still wet with distilled water, ie after a
final rinse.  Draw a vacuum, and any remaining salt will migrate to
the edges of the tape in the window areas of the reel.  You may also
have to remove an entire flange if additional rinsing followed by
vacuuming does not draw all the salts to the spoke areas of the
reel.  Wet wiping by pads will remove the salt accumulation, and
other dirt.  Follow by freon/alcohol wiping pads, to remove
remaining moisture, and let the tape dry out.  Vacuum will help this
water removal.  Finally, you should have the tape clean enough to be
rereeled again, with wiping to see if any residue remained.

We recovered tapes that had been in water 3 miles deep this way, and
the data played perfectly.  We did as a precaution, recopy the data
to new media.

Several years later, the original tape was still in playable
condition.

The first thing to corrode on metal reels are the flange attachment
screws, if the flanges are aluminum.  However salt water also will
quickly raise a whiteish deposit from the aluminum.  That is why you
keep the exposed metal wet and out of the air until you reach the
conservation lab.

Since photographic materials are wet processed, water cleaning using
caution should be acceptable.  I have done a limited amount of this
with photos, but not yet tried it on movie film.  Others might
comment on that chemistry.

Stuart Rohre
ARL:UTx