Do not try to clean moldy tape by multiple fast forward/rewind passes.  This does not work well with mold and can damage moldy tape.  Tapes with mold can often be suffering from other problems such as binder hydrolysis, binder-base adhesion failure and/or sections of the tape edge that are adhering between wraps due to action of the mold on the tape components where the mold is most active.
Here's some advice, if you want to try and treat the tape yourself:
First, to properly clean off mold, the mold must be driven into dormancy.  Attempts to wipe off active mold will often spread the contamination rather than removing it.  Dormancy can be achieved by placing the tape in an environment with low humidity for a few weeks.  We use an environmental chamber and reduce the RH to below 30%RH.
Second, the tape should be tested to determine if hydrolysis or binder-base adhesion failure is a problem.  If these are present, the tape should be treated to stabilize it before playback to avoid permanent damage to the recording layer.
It is important to always wear protective gear when handling or cleaning tapes with mold.  At the very least, you should wear latex gloves, a dust mask and some form of eye protection.  Mold can cause health problems that can be severe if someone is sensitive.  It is best to remove and clean all clothing worn during the mold removal process or to wear a smock that can be removed.  Do not hold or interact closely with small children after heavy mold exposure until you have washed any exposed skin and changed your outer clothes. 
To clean off the mold, non-dusting, non-abrasive tissue wipes can be used.  The entire surface of the tape, both front and back and head to tail, need to be wiped.  This will remove most of the flowering heads but will not remove all.  Frequently, chemical treatment is required.  You will also want to replace or chemically treat the reel. 
You can do a rough test for binder instability during early stages of the tissue wipe.  If you get a "waxy" residue or little "flakes" of tape come off on the tissues, you have a binder instability problem that may need to be addressed before continuing with the tissue wipe.
Of course, you can try these things yourself or you can send the tape to a facility that does this sort of work and has specialized equipment and technicians trained in the procedures.
We decontaminate tapes with fungus on a regular basis and would be glad to talk with you off-list if you want more information.

Peter Brothers
(201) 440-6589

Celebrating 20 Years of Restoration and Disaster Recovery Service

 -----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]]On Behalf Of Grete Pasch
Sent: Monday, July 21, 2003 8:49 PM
To: [log in to unmask]
Subject: [ARSCLIST] Advice on restoring a 1954 audiotape

I'm new to this list, so perhaps I should introduce myself briefly.  I direct the New Media department at a private university in Guatemala city.  We produce educational video and audio programs that we stream via the Internet or distribute on DVDs or CDs.  So I have many practical questions about storage formats and conditions, but today I have one specific problem on my mind.
The President of the University brought me an audiotape recorded in 1954, to see if we can rescue its contents (apparently a home recording of an important radio program).  We don't know anything about the length of the program or the recording spped.  It's a "600 ft red oxide on plastic type 651" reel. The tape and the plastic reel are both covered with hundreds of fuzzy mold dots.  I've taken some pictures:
General view:
Detail front:
Detail back:
I have found some reel-to-reel equipment that we could use to read the tape, however, how do we get rid of the mold?  I've heard two suggestions: one, fearlessly wipe the mold clean while fast forwarding the tape, using a soft cloth, then read it.  And two, mail the tape to Vidipax in NY, where it should receive the best treatment.  Any suggestions on how I should proceed?  I will really appreciate any help you all can give me!!
Saludos cordiales,
Grete Pasch -
Uni.Fco.Marroquín, Guatemala - (502) 3387875