OCR PAPER
Optical Character Recognition Paper. Similar to MICR Paper, a high-quality bond paper of good surface and dimensional stability for printing with characters for computer recognition.

OFF-MACHINE COATED PAPER
Base paper to which a mineral coating has been applied on a coating machine separate from the papermaking machine.

OFFSET BLANKET
A covering for a cylinder on a printing machine for accepting the ink image and then transferring it to the surface to be printed.

OFFSET LETTERPRESS
See Dry Offset.

OFFSET PRINTING
A method of printing in which the image on the plate is transferred to the final substrate via an intermediate surface.

OFFSIDE LAY
The sidelay opposite to the operating side of a printing machine.

ON-MACHINE COATED PAPER
Paper that has been coated with mineral matter by coating equipment installed as an integral part of the papermaking machine.

ON-MACHINE COATING
The process of covering the surface(s) of a paper with one or more layers of coating slip or other materials in fluid form, without recourse to a separate operation, the necessary equipment being an integral part of the making machine.

OPACITY
The extent to which a paper is capable of obscuring matter printed on the reverse side, an underlying page or other surface.

OPTICAL BLEACHING
See Fluorescent Whitening Agent.

OUT TURN SHEET
A sheet of paper, taken during manufacture, serving as a reference for the mill or client.

OXYGEN BLEACHING
A method of reducing the lignin content of pulp by introducing oxygen in an alkaline environment, thereby reducing the need for other chemicals in final bleaching.

OZONE BLEACHING
A method in which the lignin content of pulp is reduced by means of ozone, a triatomic form of the element oxygen. Used in combination with oxygen and hydrogen peroxide, it can with present-day technology produce almost white pulp without any chlorine chemicals. A toxic gas, it has to be removed from the exhaust gases.