Paper that has not been specifically treated to produce wet strength possesses from about 4 to about 8 percent of its dry strength when completely wetted.
By treating paper as described above, wet strength can be raised to about 40 percent of the dry strength.bursting test, or Mullen test.
Sizing paper with vegetable materials and rosinlike substances has already been described.
When paper began to be used for wrapping, consumers demanded sizing treatments that could protect the contents of the package from the effects of fluid transfer through the paper wrapping.
Even at the same weight there is a considerable difference in stiffness, chiefly due to the compactness and the amount of bonding of the sheet.porosity.
Thus, the ability of fluids, both liquid and gaseous, to penetrate the structure is a property both highly significant to the use of paper and capable of being widely varied by the conditions of manufacture.
Oil and grease resistance is attained, in fact, by reduction in porosity.
So-called greaseproof paper is made by beating an easily hydrated pulp to extremely low freeness, which results in a dense sheet with very little void space.
has a strong affinity for water), absorbent papers have a minimum of foreign materials associated with the fibre.
Of particular importance are the wood rosins that may be present in pulp and produce a self-sizing effect, especially upon aging. This reflectance is measured by an instrument that illuminates paper at an average angle of incidence of 45° and a wavelength of 457μ (microns).