Richard:
At various times, white powder or crystalline residue on magnetic tape has been identified as:
1) Cyclic tri-mers from the polyester base 2) Sodium or calcium impurities from the magnetic powder 3) Various fatty acids or sterates from the lubricant 4) Surfactants left over from the manufacturing process 5) Various external contaminants from exposure to "extreme" environments
The fatty acids and sterates will usually dissipate or be re-absorbed into the tape after a few days of exposure to a warm environment.
Most contaminants can usually be removed by the gentle and judicious application of small amounts of water, alcohol or a combination of the two.
Some residues may require other treatment but it depends heavily on whether the tape is acetate or polyester base.
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 Richard L. Hess > Sent: Tuesday, December 06, 2005 9:30 PM > To: ARSCLIST@xxxxxxxxxxxx > Subject: [ARSCLIST] Audio tape crystals > > > Hello, > > This is the latest joy I'd like to share with you all. > > http://www.richardhess.com/tape/tape_crystal.jpg > > I just received a 3" reel of 1/4" tape from one of my clients and > there were a few whitish "crystals" on it. The one in the photo is > about 42 mils across--th overall top-to-bottom of the photo is about > 50 mils (0.05 inches). There are several others, but this is the > largest. I did a little scratching at the surface as you can see from > the photo. > > This tape had been stored in Trinidad and now Beatty Nevada inside a > mobile home. > > Anyone have any thoughts about this and what damage it might be doing > to the tape and what would be the procedure for unwinding it. > > In case you are interested, the photo chain was an old AO-Spencer > microscope with a 3.2X objective and a 10x eyepiece lens and a Nikon > D100 on a microscope mount. The illumination was from a 5W Luxeon LED > in a Surefire L4 flashlight. The JPEG is a 1/4 linear (1/16 area) > reduction of the original raw file. > > Cheers, > > Richard > > Richard L. Hess richard@xxxxxxxxxxxxxxx > Aurora, Ontario, Canada http://www.richardhess.com/ > Detailed contact information: http://www.richardhess.com/tape/contact.htm