Glossary of Terms Related to Paper Making and Strathmore Products


Acid Free Paper

Paper manufactured using alkaline papermaking technology. Acid free papers are buffered with an alkaline reserve, such as calcium carbonate, to neutralize acid compounds absorbed from the atmosphere or formed through natural aging.

Archival Paper
Paper manufactured to provide the ultimate resistance against natural aging. The most important characteristics are: no groundwood or unbleached pulp, a minimum pH of 7.5 and additional alkaline reserve of 2%.


Basis Size
Sizes based on traditions/customs that represent the industry standard for a specific paper grade. For example, the basis size of watercolor paper is 22" x 30".
Basis Weight
The weight in pounds of a ream (500 sheets) of paper in a given basis size. Thus, a 140 lb. watercolor paper will be one in which a ream of 22" x 30" sheets actually weighs 140 pounds.
Artist Bristol generally describes drawing paper that is pasted. Two or more sheets are pasted together to form 2-ply, 3-ply, etc. Sheets are pasted into bristol to achieve stiffness, strength, and to form a sheet with two identical useable (felt or top) sides.


A process that takes place at the end of the papermaking machine. The paper is passed through a stack of steel rollers which gives it more uniform thickness (caliper). By varying the number of rolls used, and the pressure applied, degrees of smoothness can be achieved.
The thickness of a sheet of paper, expressed in thousandths of an inch (.001) or mil.
Center for Resource Solutions
National Non-Profit Organization that administers the Green-e program and whose goal is to increase the amount of renewable energy used world wide.
Cold Press
A term used to describe a moderately textured surface of paper used for watercolor work. 


Deckle Edge
A decorative feathered edge produced during the papermaking process.


Environmental Stewardship
Good stewardship means putting back more than we take from the environment, as well as meeting the demands of the present without compromising the needs of the future.


Felt Side
The side of the paper that does not contact the carrying wire while traveling across the wet end of the papermaking machine. Also known as the "top side", it is considered the preferred working side of a sheet of paper.
The formal name for a papermaking machine that forms a continuous web of paper on a moving wire screen. The vast majority of paper manufactured in this country is made on Fourdrinier machines.


A unit of measure for the weight of paper in the metric system. It is the weight of one square meter expressed in grams. A 140 lb.
22" x 30" watercolor paper is equivalent to 300 g/m2.
Grain Direction
The direction in which the majority of fibers lie in a finished sheet of paper corresponding to the direction the wire travels on a papermaking machine. Handmade papers have no grain direction.
Nation's leading independent certification and verification program for renewable energy and companies that use renewable energy.


A tree-free fiber used in papermaking. Hemp requires less energy to pulp, uses fewer chemicals than wood due to low lignin content and grows faster than trees. Its natural brightness eliminates the need to chlorine bleach and it can be recycled several times.
Hot Press
Used primarily in describing watercolor papers with a very smooth surface.


Laid Finish
Describes a watermarked series of parallel, vertical and horizontal impressed lines in a sheet.
An organic substance which acts as a binder for cellulose fibers in wood and certain plants, adding strength and stiffness to cell walls. Lignin is undesirable in the production of fine, permanent papers because it reacts with light and/or heat to produce henols (alcohols) and acids, which cause deterioration and embrittlement of the paper.


Mould (Mold) Made
Although originally describing a handmade process, today "mould made" papers are produced on a Cylinder machine. Cylinder machines differ from Fourdriniers only in the way the pulp is applied to the wire.


The property of a paper that minimizes or prevents the passage of light through the sheet.


This is a chemical term, defining the acid-alkaline range of any substance. A lower pH indicates acidity, a higher figure shows an alkaline condition. A pH reading of 7.0 indicates neutrality.
Plate/High Surface
For a special, uniformly smooth finish, sheets of paper are interleaved with highly polished metal plates to make a stack, or "book". The "book" is then pressed repeatedly between steel rolls under great pressure, imparting the smoothness of the metal plate to a paper's surface. Plate surface papers
A single thickness (sheet) of paper. Artists’ papers and mounting boards, as well as other grades, are identified as 1-ply, 2-ply, etc. As each ply is pasted together the increased thickness and stiffness is described by the number of plies.


Recycled Fiber
Recycled fiber is made from reprocessing waste paper. Post consumer waste (PCW) refers to paper that was recovered after actually being used by a consumer and discarded.
Renewable Energy
Renewable energy comes from sources that are continuously available, such as wind, solar, hydroelectric, geothermal and ocean tides, as opposed to exhaustible fossil fuels such as coal, oil and gas.
Renewable Energy Certificate (REC)
An authorized document or other representation (electronic, paper, etc.) of the attributes associated with generation of a defined amount of electricity, usually one megawatt-hour (MWH).
Rough Surface
A term used to describe a coarse, textured paper. Often used by artists when discussing the surface characteristics of watercolor paper.


Size (Sizing)
Additive substances such as starch, animal glue or a synthetic product which are applied to the surface of the paper (surface sizing) and/or added to the furnish (internal sizing). Sizing is applied to the paper to improve the drawing, painting or printing qualities such as moisture hold out and paper strength.
Smooth Surface
A paper with a very smooth, hard finish. Ideal for pen and ink, marker, airbrush and mechanical layouts.


Vellum/Medium/Regular/Kid Surface
A term used to describe the finish of a sheet of paper with a minimum to moderate tooth. Ideal for pencil, charcoal, airbrush, pastel, crayon, and pen and ink (not requiring a solid line).
Virgin Fiber
New fiber produced directly from wood fiber or short fibers harvested from cotton plants known as cotton linters.


Wire Side
The reverse of felt side. It is the side of the sheet of paper that comes in contact with the Fourdrinier wire on the wet end of the papermaking machine.