Tape baking - AbsoluteAstronomy.com

Tape baking is a process that is used to restore magnetic tape

Magnetic tape

Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders...

s: audio cassettes and video tapes that have begun to go through a chemical breakdown due to age, known informally as shedding. It cannot be used with acetate tapes.

How baking works

Some tapes may deteriorate because of a breakdown in the binder (the glue) that holds the oxide

Oxide

An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

particles on the tape if the tape was from either of two tape manufacturers who had inadvertently used an unstable binder formulation. That binder contained polyurethane

Polyurethane

A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...

that soaks up water and causes the urethane

Polyurethane

to rise to the tape's surface. This problem is known as the 'sticky-shed syndrome

Sticky-shed syndrome

Sticky-shed syndrome is a condition created by the deterioration of the binders in a magnetic tape, which hold the iron oxide magnetizable coating to its plastic carrier. This deterioration renders the tape unusable...

' (see references below). Short strands of urethane were most commonly used in tapes - until it was discovered that middle-sized strands are better and were good at absorbing moisture. Baking the tape temporarily restores the tape by driving the water molecules from the binder so that it can be safely copied to another tape or a different format. After baking, the tape usually remains in good condition for approximately a month. If the tape re-deteriorates, it may be possible to bake the tape again. Neither BASF nor 3M tape production used the unstable formulation, and their tape production rarely shows this type of coating instability although BASF LH Super SM cassettes manufactured in the mid-70s are prone to the problem.

When to bake tape

Tape baking is a somewhat risky procedure, since there is chance of damaging the tape from the heat. However, there are some important signs that show when a tape needs baking. The typical symptom is squealing when the tape passes the playback head

Tape head

A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa.-Principles of operation:...

or other fixed parts of a tape player. The squealing is audible directly from the tape and also transmitted electronically through the output of the tape recorder. Continuous use of a squealing tape risks permanently damaging the tape, as oxide

Oxide

An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....

is sometimes torn off the tape. This flaking residue can be seen and can feel gummy while still on the tape's surface. There is also a risk of damage to the player. Another symptom is the tape sounding dull and distorted. In a video recording, degradation can be represented by audio-visual dropouts.

Deterioration can happen to any tape, but the binder breakdown problem is more common with one brand of audio recording tape manufactured in the United States since the mid 1970s.

Methods of baking tape

There is no clear method or procedure for tape baking. Baking between 50 and 60 degrees C

Celsius

Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

(120 and 140 degrees F

Fahrenheit

Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...

) for approximately eight hours is one method. Normal domestic ovens are often not used because of their instability, but they can be used. More commonly, convection ovens or food dehydrators are used. Tom Neuman, Senior Staff Engineer at Ampex

Ampex

Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...

, knew of one extraordinary case where “a record company constructed their oven from a cardboard box, a hair dryer and a candy thermometer.” In 2002, Eddie Ciletti, Mix Magazine’s technology columnist, confessed to building a hair-dryer-powered Easybake oven to rescue his tapes. Most experts recommend not baking reel tapes wound on plastic reels, because the plastic reels can warp and become deformed; metal reels generally hold up well.

Acceptance and Alternatives

Dr. John Van Bogart at the National Media Laboratory has recommended the process, as well as the tape manufacturer Ampex

Ampex

Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...

, the sound recording industry magazine, Mix, the Association of Moving Image Archivists and the American Folklife Center

American Folklife Center

The American Folklife Center at the Library of Congress in Washington, DC was created by Congress in 1976 "to preserve and present American Folklife" . The center includes the Archive of Folk Culture, established at the Library in 1928 as a repository for American folk music...

and the Motion Picture, Broadcasting & Recorded Sound Division of the Library of Congress

Library of Congress

The Library of Congress is the research library of the United States Congress, de facto national library of the United States, and the oldest federal cultural institution in the United States. Located in three buildings in Washington, D.C., it is the largest library in the world by shelf space and...

. However, The National Recording Preservation Board

National Recording Preservation Board

The United States National Recording Preservation Board selects recorded sounds for preservation in the Library of Congress' National Recording Registry. The National Recording Registry was initiated to maintain and preserve "sound recordings that are culturally, historically or aesthetically...

has put forth their desire to find a better remedy for sticky shed syndrome. It appears the roundtable meeting of March 2006 acknowledged that there is a destructive element to tape baking. One alternative was presented in 1994. Marie O’Connell was preserving and digitizing at an archive of Radio New Zealand

Radio New Zealand

Radio New Zealand is a New Zealand public service radio broadcaster and Crown entity formed by the Radio New Zealand Act 1995. It operates news, current affairs and arts network Radio New Zealand National and classical music and jazz network Radio New Zealand Concert with full government funding...

. She began the steady application of isopropyl alcohol

Isopropyl alcohol

Isopropyl alcohol is a common name for a chemical compound with the molecular formula C3H8O. It is a colorless, flammable chemical compound with a strong odor...

to tapes with sticky shed and loss of lubricant after baking had not worked. This method appears to control friction by simultaneously keeping the tape cool and lubricated as they play. O’Connell has patented her Isopropyl Drip Machine and was the Audio Archivist at the Oral History Unit at the University of Southern Mississippi & the Chief Audio Archivist of Cups N’ Strings Studios of California. No information has been revealed about the long-term condition of the tapes once this process has taken place. Marie O'Connell is now back at Radio New Zealand Sound Archives/Nga Taonga Korero as the Analogue Tape Specialist - www.soundarchives.co.nz

Tape shedding problems

A problem common to Mylar tape was that the capstan to pinch roller pressure was such as to squeeze out the binder and oxide to form tires above and below the tape on the capstan. More frequent cleaning of the capstan was required when using new tape.

An additional problem with tape with a thickness of 1 mil or less was that the brakes on the transport had to be set so that the tape coasted to a stop. Otherwise the tape would elongate. This was also true if the initial take up and hold back tension was excessive when play was initiated.

How baking works

When to bake tape

Methods of baking tape

Acceptance and Alternatives

Tape shedding problems

External links

Further reading