Analog Tape

Paper Tape
Acetate Tape
Polyester Tape + Baking
Track Formats
Tape Speed
Equalization
Azimuth Adjustment
Noise Reduction
Cassette Tape
Handling and Storage

Analog tape came into commercial use in the US just before 1950 when major record companies began switching to the tape format for recording. Tape formulations have changed over the years, not always for the better. Most of this section deals with 1/4" analog tape.

Paper Tape
Some of the earliest tape in the U.S. was made of oxide coated paper. It appears very dark, almost black. Paper tape is dimensionally stable, which means it usually survives without curling, shrinking or twisting. Audio recorded on paper tape sounds rough because the surface texture of the paper itself prevents close, continuous contact with the playback head.

In addition, audio recorded on paper tape was typically not recorded to the edges of the tape, and so it is often described as "center track," although the term has nothing to do with the modern center track time code format.

Therefore the biggest problem in playing back paper tape is track format compatibility. Quarter track and half track playback heads miss much of the audio. The best solution is to use the two inside tracks of a 4 channel playback head, or a full track playback head. The use of proper playback heads is important to minimize the textural problems of paper.

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Acetate Tape
Acetate tape does not always age well. To determine if a tape is acetate-based, hold the reel up to the light. If it appears translucent when looked at from the edges, then it is acetate.

Acetate tape was popular from about 1950 through the mid 1960's. As it decomposes over time, the tape curls, shrinks and becomes lighter in mass. Deteriorated acetate tape puts off an odor of acetic acid (vinegar), and feels substantially lighter in weight in comparison to non-deteriorated acetate tape. Deterioration is thought to be storage related, but even properly stored tape will have problems on occasion. Tape ends that are not secured during storage will suffer damage first on the ends that are left loose.

Playback can be especially problematic, and the only way to play severely deteriorated acetate tape is to increase tape tension in order to maintain proper tape to head contact. Acetate tape in an advanced state of decomposition can be curled so badly that it will jump out of the tape guides entirely; but one of the features of acetate tape is that it breaks cleanly and does not deform readily, so tape tension can be made quite high without stretching the tape. The method to achieve this increased pressure is limited only by your imagination, based on your machine. Increased tape tension will cause accelerated tape head wear and playback speed fluctuations, but there is often no other way to play such tape.

Sometimes badly decomposed acetate tape cannot be returned to its original reel after playing because the tape deformation prevents a proper tape pack on the reel. Sometimes the solution is to increase tape tension during rewinding or fast forwarding, or to simply store the tape on two reels.

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Polyester Tape + Baking
Polyester or mylar based tape is opaque when held to the light and viewed from the side. Polyester tape will deform permanently before it breaks, so be careful not to stretch it.

Generally, polyester tape has a superior tape base, and oxide/binder formulations have steadily improved over the years to prevent oxide from flaking off, with one big exception: serious problems occurred on certain tapes manufactured from roughly 1975 to 1990 (and even later). The problem is known as "sticky shed syndrome."

Tapes with "sticky shed syndrome" leave a waxy residue on rollers, heads and guides, which destroys high frequency response and can eventually cause a tape player to stop entirely.

If a tape is suspected of having "sticky shed syndrome," it should be treated before playing. Playing untreated tapes damages them, because it smears part of the binder containing the oxide and reduces high frequency response. In severe cases the binder will totally separate from the base.

Any backcoated tape manufactured after about 1975 is suspect. To diagnose the tape, create a roller only path, and rewind the tape slowly. Good tape comes off the supply reel at a near perfect tangent, but sticky shed syndrome will cause tape to stick slightly to the pack as it is pulled away. You can also hold a finger against the oxide side during rewind (be careful - it's easy to cut your finger), and if you detect any friction, or if your finger picks up any residue, then the tape has "sticky shed syndrome." Stop rewinding.