A typewriter ribbon or ink ribbon is an expendable module serving the function of transferring pigment to paper in various devices for

impact printing In computing, a printer is a peripheral machine which makes a persistent representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Differ ...

. Such ribbons are part of standard designs for hand- or motor-driven

typewriter A typewriter is a mechanical or electromechanical machine for typing characters. Typically, a typewriter has an array of keys, and each one causes a different single character to be produced on paper by striking an inked ribbon selectivel ...

teleprinter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Init ...

s, stenotype machines, computer-driven printers and many

mechanical calculator A mechanical calculator, or calculating machine, is a mechanical device used to perform the basic operations of arithmetic automatically, or (historically) a simulation such as an analog computer or a slide rule. Most mechanical calculators we ...

s. The module consists of a length of a medium, either pigment-impregnated woven ribbon or pigment-coated

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

tape, and a transport mechanism involving two axles. At any given moment, most of the length of the medium is wound as a close-spaced spiral around one axle or the other, tight enough for friction among turns to make it behave mostly like a solid cylinder. Rotation of the axles moves the ribbon or tape after each impact and usually aids in maintaining tension along the roughly straight-line path of the medium between the axles. The module may itself include mechanisms that control the tension in the temporarily unwound portion of the medium. Some typewriter ribbons have two different coloured pigments (usually black and red) which could be selected if the typewriter had a switch to allow for words or sentences to be written in a different colour when required.

Reversing ribbons

Woven typewriter ribbons were the earlier variant. With them, the pigment is an

ink Ink is a gel, sol, or solution that contains at least one colorant, such as a dye or pigment, and is used to color a surface to produce an image, text, or design. Ink is used for drawing or writing with a pen, brush, reed pen, or quill. Thicker ...

that dries on typing paper but not on the ribbon, and the ribbon is mounted at each end to a

flange A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength (as the flange of an iron beam such as an I-beam or a T-beam); for easy attachment/transfer of contact force with another object (as the f ...

d reel whose hub engages with one of the axles. Only the axle onto which the ribbon is winding is driven, and the ribbon module is intended to work with an axle-driving mechanism that reverses the direction of rotation when the undriven axle reaches the point where there is no ribbon left wound around it. Thus, the full length of the ribbon shuttles back and forth between reels, and each position along it is struck twice in each cycle of the ribbon's motion (once in the right-to-left phase and once in the left-to-right). An operator who judges a ribbon's ink supply to be depleted to a point of marginal acceptability typically manually winds the whole ribbon onto the fuller reel, releasing it from the empty one, discarding the ribbon the reel it is wound on, and replaces them with a new ribbon that is purchased already wound on a single compatible reel. Typically the attachment between reel and ribbon involves one

grommet Curtain grommets, used among others in shower curtains. A grommet is a ring or edge strip inserted into a hole through thin material, typically a sheet of textile fabric, sheet metal or composite of carbon fiber, wood or honeycomb. Grommets ar ...

at each end of the ribbon that pierces the ribbon and engages with a hook on the hub of the corresponding reel.

One-time ribbons

The

IBM Selectric typewriter The IBM Selectric typewriter was a highly successful line of electric typewriters introduced by IBM on 31 July 1961. Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a typical typewriter of the peri ...

required ribbons of polymer tape and made them common. With them, the entire impacted area of the pigment coating adheres to the paper and peels off of the ribbon, producing typed copy with greater uniformity of character shape, reflecting sharper contrast between the unmarked paper and the pigmented characters compared to cloth ribbons. This full-depth shedding of the pigment renders multiple passes over the length of the ribbon unworkable, and the module is discarded after a single pass through its length. Deducing what has been typed by inspection of the ribbon is far more practicable and reliable than with a cloth ribbon, so some users ensure destruction of discarded one-time ribbons in order to prevent unintended disclosure. {{Authority control Typewriters