Questions related to Paper

What are the Main Characteristics of Paper?
Main characteristics of Paper:- Tensile Strength, Bursting Strength, Tearing Strength, Folding Endurance, Optical Characteristics include Brightness, Opacity, Transparency, Gloss. Structural Properties: Basis Weight and Gram mage, Thickness, Formation, Smoothness, Porosity.

What is Brightness of Paper ?
It indicates the degree of whiteness. It is a measurement of reflectance by White or near White Paper at a single wave-length, 457 nm (blue region of visible spectrum). It is a test to measure effectiveness of bleaching in removing yellowness from pulps and for measuring ageing of paper.

What is Opacity ?
Property of a paper sheet which obstructs the passage of light and prevents one from receiving through the sheet, objects on or in contact with the other side.

What is Porosity and Bursting Strength?
Porosity:- Property of containing connected air voids. It is dependent upon the number of voids and their distribution in size, shape and orientation. It indicates how a sheet will respond to fluid penetration eg. In printing paper how printing inks will penetrate and spread. Greaseproof paper must have a very low air permeability/porosity in order to perform properly. Cigarette paper must have controlled permeability so as to give a uniform burning rate.

Bursting Strength:- A measure of the ability of a sheet to resist rupture when pressure is applied to one of its side. This is one of the oldest tests used by the paper industry and is relatively easy and inexpensive to run for quality control.

What is Grammages/sq.mt. (gsm) ?
Weight of paper of 1 sq. mtr. area in grams, i.e gms per square meter abbreviated as gsm or grammage. In the production and conversion of paper, two characteristics of utmost importance are weight and area.

Is there any difference between paper and cartonboard?
In terms of structure, paper has one layer, whereas cartonboard has several. Furthermore, paper and cartonboard are divided into different categories on the basis of their grammage range and structure. Material with a weight of 180 gsm and above is classified as cartonboard.

What is recycling?
Recycling is the recovery of a product, which, having been through its original life cycle, is then re-processed and transformed into another product.

What is more important-- whiteness or brightness?
If you want to have more impact-- focus on whiteness. Whiteness is more important and accurate with regard to the human perception of quality and uniformity of paper than is brightness. Whiteness is the best descriptor of the appearance of white paper.
Brightness measures a narrow band of colour
Whiteness measures the total colour spectrum.

What is an acid proof paper?
A paper that is not affected by acid physically or chemically. This paper is used with substance containing acid.

In which direction paper is weaker and more sensitive to changes in relative humidity?
In the cross direction paper is weaker.