Print-through

Print-through (sometimes referred to as bleed-through) is a generally undesirable effect that arises in the use of magnetic tape for storing analogue information, in particular music.

Explanation

Print-through is a category of noise caused by contact transfer of signal patterns from one layer of tape to another. Print-through can take two forms: 1) thermo-remanent magnetization induced by temperature, and 2) anhysteretic magnetization caused by an external magnetic field.

The former is unstable over time and can be easily erased by rewinding a tape and letting it sit so that the patterns formed by the contact of upper and lower layers begin to erase each other and form new patterns with the repositioning of upper/lower layers after rewinding. This type of contact printing begins immediately after a recording and increases over time at a rate dependent on the temperature of the storage conditions.

Audibility

The audibility of print noise caused by contact printing depends on a number of factors: 1) the amount of print due to conditions of time and storage; 2) the thickness of the base film that acts as magnetic barrier (thin C-90 cassette tapes are more susceptible than studio mastering tapes that use a base film four times thicker); 3) the stability of the magnetic particle used in the tape coating; 4) the speed of the tape (the wavelengths of the prints shift so that higher speeds move printed signal closer to the range where the ear is more sensitive); the dynamics of the musical program (very quiet passages adjacent to sudden loud signals can expose the print signal transferred from the loud signal); and the wind of the tape (A-winds for cassettes with the magnetic layer facing outward have stronger print signals after a loud signal--"post-print"--than B-winds used in modern open-reel recorders that have stronger "pre-print" signals preceding a loud passage. echo.