Imposition
The laying out of type pages in a press form so that they will be in the correct order after the printed sheet is folded. Imposition planning can help reduce paper waste and make-ready time. The most common imposition approaches are sheetwise, work-and-back, work-and-tumble and work-and-turn. See specific name for definitions.

Impression
Pressure of type of blanket as it comes in contact with paper.

Impression cylinder
In printing, the cylinder on a printing press against which the paper picks up the impression from the inked plate in direct printing, or the blanket in offset printing.

Imprint
To print other information on a previously printed piece by running it through a press again.

Imprinter
An auxiliary printing unit, usually employing rubber letterpress plates. Imprints copy on the top side of the web and permits imprint copy to be changed while the press is running at full speed.

Index paper
A stiff, high-bulk, low-weight paper that is a popular choice for business reply cards. An inexpensive, smooth finish paper; typically comes in the basic size of 25 1/2" x 30 1/2".

Ingredients of paper
Paper is composed of cellulose fibers, such as from wood or cotton, and additives, such as fillers, dyes and sizing.

Ink
Printing inks are made up of pigment, pigment carrier and additives formulated to reduce smudging, picking and other printing problems associated with ink. The choice of ink depends on the type of paper and printing process.

Ink absorption
A paper's capacity to accept or absorb ink.

Ink dot scum
On aluminum plates, a type of oxidation scum characterized by scattered pits that print sharp, dense dots.

Ink drum
A metal drum, either solid or cored. A part of an inking mechanism used to break down the ink and transfer it to the form rollers.

Ink fountain
In printing presses, the device which stores and supplies ink to the inking rollers.

Ink gloss
An ink that contains extra varnish, which makes the ink appear glossy when printed.

Ink holdout
The way the ink pigment sits on the surface of the paper. Strong ink holdout results in a sharp, bright image. An inked image printed on paper with a high degree of ink holdout will dry by oxidation rather than absorption. Also, ink resistance or the ability of paper to resist penetration of the ink.

Inkjet printing
In digital printing, a plateless printing system that produces images directly on paper from digital data using streams of very fine drops of dyes, squirted under pressure from a printhead containing one or more nozzles, which are controlled by digital signals to produce images on paper. The printer's resolutions (often expressed as dots per inch, or dpi) are dependent upon a number of factors, such as the number of nozzles, the frequency of ink droplets, the placement of the droplets and the qualities of the paper used for printing.

Inking mechanism
On a printing press, the ink fountain and all the parts used to meter, transfer, break down, distribute, cool or heat, and supply the ink to the printing members. Also called inking system.

Inside side seam (envelopes)
Single seam construction on open-end envelopes where the seam glues beneath the back panel. Allows full printing on back of envelope. Can be on left or right side (LISS or RISS).

Inside tint (envelopes)
Printed design on the inside of the envelope, used for added opacity and/or graphic interest.

Insert
A printed piece prepared for insertion into a publication or another printed piece.

Intaglio printing
Printing method in which type or design is etched into a metal plate as opposed to raised letters, as in letterpress. Also called Gravure (see definition).

Intensity
The extreme strength, degree or amount of ink.

Interleaves (slip sheets)
Paper inserted between sheets as they come off the printing press to prevent transfer of wet ink from one to the other. Also, accessory sheets between parts in a form.