Print-through is a generally undesirable effect that arises in the use of magnetic tape for storing analog information, in particular music, caused by contact transfer of signal patterns from one layer of tape to another as it sits wound concentrically on a reel.
Print-through is a category of noise caused by contact transfer of signal patterns from one layer of tape to another after it is wound onto a reel.
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.
Depending on tape formulation and type, a maximum level will be reached after a certain length of time, if it is not further disturbed physically or magnetically.
Digital tapes can also be affected by contact print effects in a phenomenon known as "bit-shift" when upper or lower layers of tape cause a middle layer to alter the pulses recorded to represent binary information.
While print-through is a form of unwanted noise, contact printing was used deliberately for high-speed recording (duplication, high speed en masse copying) of video tape, instead of having to record thousands of tapes on thousands of VCRs at normal playback speed, or recording the source material repeatedly in real time to large reels (without end caps) of tape (called pancakes) over 48 hours long to be inserted into cassettes.
[2] DuPont[3] in conjunction with Otari[4] invented a form of thermal magnetic duplication ("TMD") by which a high-coercivity metal mother master tape was brought into direct contact with a chromium dioxide copy (slave) tape.