Paper

The purpose of this article is to give a brief understanding of paper and how it is important to scrapbook paper and cardstock.

Paper has played a key role in cultural as well as in the industrial advancement of mankind.  Since as early as 3000 BC, having evolved into a number of forms, the Egyptians gave the world the first form of writing paper in form of Papyrus. Modern papermaking was introduced in 105 AD in China by Ts'ai Lun, using macerated bark of trees, hemp waste, old rags and fish nets. Its evolution has brought about different kinds of paper used specifically for various purposes.

The process of papermaking can be broken down into three steps:

• Making the fiber
• Forming the sheet
• Drying

The first step involves making pulp of the component material, a concentrated mixture of fibers in liquid. Once the fibers have been extracted, some artificial ingredients may be added to alter the final appearance of the product such as pigment for color, calcium carbonate for opacity and others to achieve particular qualities. The pulp mixture, once obtained is further diluted with water resulting in thin slurry. This diluted slurry is drained using a fine-mesh moving screen. The idea is to make a fibrous web. A watermark can also be impressed into the paper at that time. This web is continually moved, pressed and then dried into a continuous sheet.

The Mould Process is somewhat different. Here, a quantity of pulp is placed into a form, using a mesh base, such that the fibers form a sheet on the mesh and excess water can be drained. Applying pressure at this point helps to remove additional water. It may then be removed from the mould, wet or dry, and then on to further processing.

When paper is produced in large quantities, typically, a Fourdrinier machine uses a horizontal wire-screen belt to filter the stock. After drying, this continuous web may be cut into rectangular sheets by slicing the web vertically and horizontally to the desired size. The sheet sizes are prescribed by International Organization for Standardization (ISO).  Various standard paper sizes like A4 etc. are cut in specified dimensions as established by ISO.

Paper is qualitatively marked per its physical characteristics, optical properties and other miscellaneous properties such as pH etc. Some of the characteristics that distinguish the qualities are:

Physical Properties:

• Basic Weight or Grammage: The basic weight is the weight per unit area. This can be expressed as the weight in grams per square meter (GSM or g/M2), pounds per 1000 sq. ft. or weight in kgs or pounds per ream (500 sheets).

• Bulk: It indicates volume or thickness in relation to weight. It is defined as the reciprocal of density. It is calculated from caliper and basis weight. Bulk (cubic centimeter/g) = Thickness (mm)* Basis Weight (g/m2) * 1000.

• Caliper: Thickness or Caliper is measured with a micrometer as the perpendicular distance between two circular, planes, parallel surfaces under a pressure of 1 kg. / CM2.

• Curl: This can be defined as a systematic deviation of a sheet from a flat form. 

Optical Properties:

• Brightness, Whiteness and Color: Brightness is defined as the percentage reflectance of blue light only at a wavelength of 457 nm. Whiteness refers to the extent that paper diffusely reflects light of all wave lengths throughout the visible spectrum. Whiteness is an appearance term. Color is basically an aesthetic value.

• Opacity: Opacity is the measure of how much light is kept away from passing through a sheet.

Strength Properties:

• Bursting Strength: Bursting strength tells how much pressure it can tolerate before rupture. It is important for bag paper.

• Hardness: The degree to which it will resist indentation by some other material such as a stylus, pen or printing plate.

All of these characteristics are used to mark the quality of paper. Based on these properties as well as usage, different kinds of paper supplies have evolved for the market. Let’s look at some of them:

Air mail paper

• It is light weight, thin and mainly wood free for writing, used for air mail. It is made in an anaerobic treatment process employing micro-organisms to reduce organic matter in waste water without any oxygen.

Art paper

• This is rather high quality, heavy, two-side coated printing paper with smooth surfaces. The reproduction of fine single and multicolor pictures is possible as it has an even, well closed surface and a uniform ink absorption

Banknote paper

• It is age-resistant suitable for 4-colour printing, with a watermark and other falsification safeguards such as embedded metal strip also. It often contains cotton fibers.

Bible paper

• Is wood free, may also contain rags, and is a specialty printing paper with a low grammage, mostly with high filler content. 

Blotting paper

• It is bulky, highly absorbent, filler-free paper and is mostly produced from pure cotton in the form of bleached linters and from chemical pulp.

Calendered paper

• Smoothed and compacted, it is thus more or less glossy (may be sharp or matt calendered). The specific effect produced in the calendar unit is the result of friction combined with temperature and pressure.

Light-weight printing paper

• Light-weight paper has a low grammage and is made from rags and bleached with craft pulp and is used for advertising material (like catalogues, leaflets, etc.).  It might also be used for commercial jobbing work (like magazines, brochures, instruction leaflets, forms etc.)

Lignin Paper

• The paper yellows in sunlight. Lignin is a natural "adhesive" which binds wood fibers together in the tree and imparts rigidity. Pulp brightness depends on the amount of lignin remaining in the pulp.

     Vellum

• (from the Old French Vélin, for "calfskin") is a sort of parchment characterized by its thin, smooth, durable properties. Strictly speaking, vellum should only be made from calf-skin, but the term early on was used for the best quality of parchment regardless of the animal from which the skin came. There is also modern imitation "vellum" made out of cotton, although a small amount of true vellum is still made.