Re: [ARSCLIST] powdery substance on 2" tape

["Peter@xxxxxxxxxxxxx" <lists@xxxxxxxxxxxxx>]

Heath:

The pictures are not that clear and it could well be fungus but the general
shape of the "clumps" of contaminants are more consistent with other
problems.  White powdery substance found on tape has been identified in the
lab as a number of different compounds, other than fungus, including: cyclic
tri-mers from the polyester, sodium or calcium impurities from the magnetic
powder, various fatty acids or sterates from the lubricant and surfactants
left over from the manufacturing process.

Most fungus does not manifest as a "powdery substance" but as patterned
colonies or thread-like groupings.  The fatty acids and sterates from the
lubricant usually appear as distinct crystalline structures after the tape
has had long-term exposure to very low temperatures and will usually sublime
or be re-absorbed into the tape after exposure to room temperature for 24 to
48 hours.  A white powdery substance is most likely to be calcium, sodium or
surfactant residue that has migrated to the tape surface.

What temperature/humidity conditions were the tapes stored at and is the
residue strictly "powdery" or does it show some crystalline or thread-like
structure?

If you do identify the contaminant as fungus, it is important to make sure
the fungus is dormant before attempting to remove it.  Active fungus will
tend to "smear" if wiped with pellon.  Dormant fungus will be much easier to
remove.  Dormancy can be achieved by isolating the tape in an environment
with a low RH (we prefer below 30%) for approximately one week.

If the contaminant is not fungus, as I suspect from your description and the
pictures, do not "bake" the tapes.  Baking will increase the presence of
manufacturing residues on the tape surface rather than reduce them.

The residues left over from manufacturing can be removed by wiping with a
tissue.  Care must be taken, however, as the volume of these residues is
often such that they will quickly clog the tissue and re-deposit on the
tape.  Cleaning of these residues (and fungus) is more effective if both a
tissue wipe and burnishing can be applied.  Also note that once the residues
have begun to emerge from the tape, they will continue to emerge for a
period of time.  Once the tape has been cleaned, it should be copied as soon
as possible, before more residue can appear.

Peter Brothers
President
SPECS BROS., LLC
(201) 440-6589
www.specsbros.com

Restoration and Disaster Recovery Service Since 1983

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of Heath Condiotte
> Sent: Tuesday, April 19, 2005 2:24 PM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: [ARSCLIST] powdery substance on 2" tape
>
>
> Hello all,
>
> http://img.photobucket.com/albums/v663/heath4242/whitepowderontape.jpg
> http://img.photobucket.com/albums/v663/heath4242/whitepowderclose.jpg
>
> The above links point to two pictures of a reel that contains a powdery
> substance we have never encountered before.  I'm wondering if any of you
> have dealt with this and have any suggestions? Here are the pertinent
> details:
>
> -Ampex 456 from circa 1977 (at least that was the record date--the stock
> could be older)
> -No apparrent water damage
> -Tapes have been stored in a climate controlled, stable vault for at least
> the past year.  Prior to that time, we do not know where these tapes were
> located
> -The white powder wipes off rather easily when touched
> -The powder covers all edge surfaces of the tape--not just the openings in
> the flange.  When the flange is removed, the substance is on the
> entire edge
> surface.
>
>
> Would a pellon cleaning be a sufficient method of prepping these tapes for
> back up? Or would more processes need to be performed? Our
> caution is based
> on our assumption that these tapes will need baking (they are from a
> suspicious batch), and although we have treated mold and water
> damaged tapes
> before, this substance is new to us.
>
> Thanks in advance for any input
>
> Heath Condiotte
> Audio Engineer
> Xepa Digital
> www.xepadigital.com
> hcondiotte@xxxxxxxxxxxxxxx
> (724)794-3686 phone
> (724)794-3292 fax
>
>