Key characteristics of copy paper include thickness, moisture content, opacity and brightness.
Paper thickness is defined as the perpendicular distance between two opposite surfaces of a sheet. Thickness is one of the most important properties and affects many things, including bending resistance. In turn, bending stiffness influences the passage of paper through the printer. Thin paper often shows low resistance. It runs the risk of jamming while paper passes through the office equipment.
High thickness paper is more rigid. Its relative stiffness also increases the risk of jams, since paper cannot bend properly when it goes around shafts, drums, photoreceptors, rollers and turning areas. For standard 80 g office paper, sufficient thickness is at least 100 microns.
The moisture content is the amount of water in the paper. Moisture content is an important factor as moisture affects processing, printing and copying.
With the electrographic (xerographic) printing method, the paper is heated when toner is fixed. Therefore, if the moisture content exceeds 5.3%, the paper tends to curl and wave. It prevents double-sided printing and negatively impacts the quality of printed documents.
Moisture content also directly affects the electrical conductivity of paper. and influences its resilience. 4.0–5.2% is the best moisture content range for office papers.
Opacity. Double-sided printing requires opaque paper. The opacity of paper should be at least 90% to ensure the desired result, i.e. to let through almost no light, so that the text or other visual elements on one side of a sheet are not visible on the reverse side.
Brightness. Brightness refers to the capacity of paper to reflect equally all the colors of the spectrum. Paper is supposed to reflect light from all wavelengths of the entire visible spectrum. If a sheet of paper is really white, it has high reflectivity. In this case, it absorbs waves of different length equally.
The whiteness value is determined in accordance with the requirements of the International Commission on Illumination (CIE) and corresponds to the visual perception of white paper, whether or not it contains fluorescent whitening substances observed with a daylight source (for example, C / 2 ° or D65 / 10 °).
All measurements of optical characteristics are directly dependent on the light source and the observer. The light source is standardized according to temperature value (“temperature of light”) defined in Kelvins (K). Since natural daylight is characterized by a non-constant spectrum, which depends on time, place, weather, and other case-specific factors, standard daylight sources have been designed to ensure compliance with reproducible conditions.