It is a high resistance paper type made of softwood trees such as pine, fir and spruce with long fibers by using the sulphate process. Kraft paper is usually produced in unbleached, i.e. in natural colors.
Kraft paper can be produced as entirely white or by bleaching using white cellulose only on the surfaces as White Top. Their busting values, which show the resistance, may vary between 3,5-5 kPa and their weights may vary between 100-450 gr/m².
These are two or three layer liner paper that is obtained by adding unbleached or white primary or secondary fiber on recycled old paper fiber. It is commonly used in today's world where recycling is of great importance. Their busting values may vary between 2--3,5 kPa and their weights may vary between 90-125 gr/m².
This paper type, which is produced partially mechanically and partially chemically from hardwood short fiber trees such as birch, betula pendula, eucalyptus, is used for producing the fluting layer on corrugated cardboard.