The appearance properties are related to the visual impression of the paperboard surface.
One of the essential requirements of the paperboard is that it should be printable. This means that it must be capable of meeting specific targets in terms of its appearance and performance during, and as a result of, the printing process.
In this manual the term printability refers to the visual impact from the images printed on the paperboard. The term print runnability is used to describe the performance of the paperboard during printing and converting.
The following is discussed in this chapter:
• coating contents
• surface structure and smoothness
• unwanted surface defects
• printability and varnishability
• absorption, setting, drying
• rub resistance
• surface strength.
The measurable properties listed below are those which are usually used when providing a technical description of a paperboard grade. The methods described are those in common use. They are also used by Iggesund Paperboard.
For further information about specific apparatus, please see the manufacturers’ product catalogue (e.g. Lorentzen & Wettre).
The test methods for the properties listed are described in the following pages:
• surface strength
• IGT Surface strength
• Dennison number
• surface tension
• whiteness and brightness
• surface roughness
• surface pH
• ink absorption
• L*, a*, b* coordinates.