Moldy, Moldy, Moldy!
Another reader, Charlie Mayer at Swarthmore College, wrote asking what to do with archival tape that is growing yellow, green and white mold. Apparently this mold is not of the school colors. Ampex's Tom Neuman provided a ready recipe for restoration:

Open all affected boxes and remove the reels.
Place the opened boxes and tapes in a dry, warm room so that the tapes can thoroughly dry. This may take anywhere from a few days to a couple of weeks.DO NOT bake tapes that have mold growth, as this will just bake the mold into the tape, and permanently stain the surface of the tape!

After the tapes are thoroughly dry remove the flanges, if the tapes are on metal reels, and thoroughly clean the mold off with a 3% solution of Hydrogen Peroxide. This can be purchased at any drug store. Hydrogen Peroxide will effectively clean off the mold and its antiseptic properties will help to inhibit future mold growth (It also comes in handy if you cut yourself while removing the flanges). It is especially important to thoroughly clean any stick-on labels that may be on the flanges as they seem to be great breeding grounds for mold.

Next comes the awful part; load the reel of tape on a transport (after replacing the flanges) and slowly wind the tape forward by hand and inspect the surface for sign of mold. If any mold is seen it can be wiped off with the 3% Hydrogen peroxide solution and a TexWipe or similar lint-free cloth. Follow by wiping the excess liquid off with a dry wipe. Pay particular attention to the edges of the tape as this is where mold growth generally starts. The time this step will take varies greatly dependent on the severity of the mold growth and your patience.

If the entire tape is affected you can use a slightly damp (with Hydrogen Peroxide) cloth held up against both sides of the tape and run the tape through at the slowest speed you have available. If you use this method, make sure that you repeat the process several times with a dry wipe to completely dry off the tape's surface before putting the tape back in storage.
Hydrogen Peroxide is the only material we can recommend for cleaning the surface or backcoat of a tape. It does not damage any of the tape's chemical components and is safe to the user. DO NOT use alcohol or other types of cleaning solvents as they may permanently damage the tape! In many cases the surface of the tape may be stained from the mold even after cleaning. This has not proved to be a functional problem, just a cosmetic one.

Finally, thoroughly clean the storage box with Hydrogen Peroxide and dry thoroughly. Quite often the box is thoroughly damaged, and a new box may be needed. In the case of historical material the original box may need to be cleaned and stored separately from the tape. Mold growth usually initiates from moisture trapped in the box material or inside the box.

Before putting your tapes back into long-term storage make sure there is no trapped-in moisture inside the box. It is not a good idea to put tapes away when the humidity and temperature are high, as this is the air that will be trapped inside the box for the next 20 years.

Neuman says he has personally cleaned dozens of tapes using this method and it seems to work quite well.

We wish clean, dry, securely bindered tape to you all.

Author's note: Since these articles were published in 1995, the tape industry has changed dramatically; 3M no longer manufactures recording media, and the division of Ampex that made recording tape has been spun off, and is now known as Quantegy.