A

Acid Free (Neutral pH):

Papers that are without acid in the pulp. Acid free papers have a pH of 7.0. If prepared properly, papers made from any fiber can be acid free.

Antique:

A printing paper with a rough finish but good printing surface, valued in book printing for its high volume characteristics.

Archival Paper:

A paper with long-standing qualities, acid free, lignin free, usually with good color retention.

B

Buffering:

The neutralizing of acids in paper by adding an alkaline substance (usually calcium carbonate or magnesium carbonate) into the paper pulp. The buffer acts as a protection from the acid in the paper or from pollution in the environment.

C

Cellulose:

The chief constituent of the cell walls of all plants. All plants contain tissue that, when properly processed, will yield cellulose. Cotton in its raw state contains about 91% and is the purest form of natural cellulose. Other sources for papermaking include hemp (77%), softwoods & hardwoods (57% to 65%), and kozo (66% to 77%).

Cold Pressed:

A paper surface with slight texture produced by pressing the finished sheet between cold cylinders.

Cotton Linters:

Fibers that adhere to cottonseed after ginning. Used as raw material to produce pulp for cotton fiber content papers.

D

Deckle Edge:

The feathery edge which is the result of the natural run-off of wet pulp when making handmade and mouldmade paper, or the result of sheets being torn when wet. The edge is simulated in machine made papers by cutting them with a stream of water when still wet.

E

Embossed:

Many art and watercolor papers have a raised in relief logo or identifying name pressed into one corner of the parent sheet.

G

Grain:

Direction of fibers in a sheet of paper. Long grain describes fibers running parallel to the longest side of a sheet. short grain running parallel to the short side.

Grams per square meter (Grs/m²):

The gram weight of a hypothetical square meter of a particular type of paper, a good comparative measure because it does not vary with sheet size, sometimes abbreviated as just "gsm" or "g/sm."

H

Handmade Paper:

Paper made by hand using a mould (a frame covered with a flat, rigid screen or flexible screen). In both cases the mould is covered by a flat frame called a deckle, to contain the run-off of wet pulp, dipped into a vat of wet pulp, shaken to distribute the fibers evenly and drained of its excess water. The wet mat of fibers remaining in the newly formed sheet is then dried against blankets & may be hot pressed, cold pressed, or air dried.

Hot Pressed:

A paper surface that is smooth, produced by pressing a finished sheet through hot cylinders.

High Alpha Cellulose:

A very pure form of wood pulp which is considered to have the same longevity as cotton or other plant fibers.

L

Laid Papers:

Papers with a "grid" pattern in the sheet, resulting from the pulp resting against wires on the papermaking mould screen. "Laid" lines are closely spaced while "chain" lines are farther apart & run parallel with the grain direction of the sheet, important when folding papers, especially to bookbinders.

Lignin:

A component of the cell walls of plants that occurs naturally, along with cellulose. Lignin is largely responsible for the strength and rigidity of plants, but its presence in paper is believed to contribute to chemical degradation. To a large extent, Lignin can be removed during manufacturing.

M

Machinemade Paper:

Paper made on a very rapid running machine called a "Fourdrinier", producing consistent quantities of sheets or rolls.

Mouldmade Paper:

Paper made by a slowly rotating machine called a cylinder mould that simulates the hand-papermaking process. Fibers become more randomly intertwined than in machinemade papers, producing a stronger, more flexible sheet or roll.

P

Parent sheet:

The original sheet size that comes off the mould machine, from which can be cut smaller sheet sizes. Most watercolor and art papers have a 22x30" parent sheet size.

Ply:

A single layer of paper. A term used when several sheets of paper are laminated together to form a board.

Pulp:

Any cellulose plant fiber cleaned and beaten into a wet mixture used to form sheets of paper.

pH:

In chemistry, pH is a measure of the concentration of hydrogen ions in a solution, which is a measure of acidity or alkalinity. The pH scale runs from 0 to 14 and each number indicates a ten fold increase. Seven is pH neutral: numbers below 7 indicate increasing acidity, with 1 being the most acid. Numbers above 7 indicate increased alkalinity with 14 being the most alkaline. Paper with a pH below 5 is considered highly acidic. Buffered papers typically have a pH between 8.5 and 9.5.

R

Rag:

Formerly the principal raw material used in the making process; often meaning cotton rags. Rag content describes the amount of cotton fiber relative to the total amount of material used in the pulp. "Rag content" is not widely used (or is a misnomer) today as more and more high quality paper is made not from rag but from linters.

Rice Paper:

A common misnomer used to describe Oriental papers. There are no papers made from rice, although rice starch was traditionally used to size papers made of Kozo (mulberry plant), Gampi, or Mitsumata.

Rough:

A heavily textured paper surface produced by placing wet sheets of paper against textured blankets or air drying (or both).

S

Size or Sizing:

The process by which gelatin rosin, starch or other synthetic substance is added to paper to provide resistence to the absorption of moisture or eliminating ink feathering and bleed through. Sizing added to the beater or vat of pulp is known as internal sizing. After a sheet is formed, it may be either surface sized (painted or brushed on the surface), or tub sized (immersed in a bath).

Sulphite:

Sulphite pulp is produced from the wood of coniferous trees. Wood chips are cooked in calcium bisulphate or sodium sulphite, and bleached, producing fairly long strong fibers. Since the end of the 1860's until recent years, it has been the most widely used pulp in America. In fact, the term"sulphite" has become generic and is still accurately used to describe any paper made from wood in distinction from papers made from cotton or other fibers. Sulphite pulp is available in a range of grades up to pure alpha cellulose.

V

Vellum:

A paper surface that is finely textural. Vellum is also used to designate heavy weight, translucent drawing of drafting papers.

W

Watermark:

The translucent design or name easily visible when a sheet is held to the light. A design is sewn onto the papermaking screen with raised wire. When the sheet is formed, the pulp settles in a thinner layer over the wire design.

Wove paper:

Papers which show no fine "laid" lines running through the sheet when held to the light.