The resistance of corrugated fiberboard shipping containers to damage by moisture is improved by wax treatment, and a common practice involves a light wax saturation applied to the medium and facings, followed by a curtain coating or roll coating operation applying wax to the surface. The functional performance of the board is dependent upon the amount of wax deposited in each operation.

5.1.1 For the wax impregnation within the facing, the principal concern is with the weight of wax used relative to the weight of paperboard present, that is, the weight percent loading or pickup. This method measures that loading and assumes that the loading is distributed uniformly throughout the facing. However, the method does not provide a measure of the weight of impregnating wax per unit area, since not all of the facing fibers are utilized in the testing.

5.1.2 For the wax coating the principal concern is in the weight of wax present on the surface per unit area. This method measures the amount of material applied, and assumes that the major portion of molten coating applied will congeal and remain on the surface, without undue migration into the fibrous structure of the medium.

Note 2-In a typical curtain coating application, a portion of the coating will partially migrate into and become embedded in the fibers of the facing to the extent of about 10 % of the coating applied.

5.1.3 These procedures involve extractions of designated sections of the paperboard and determination of the extractable material reported as wax. This assumes that the nonwax extractables in the paperboard substrate are in negligible amount (for example, about 0.2 weight %).

Note 3-If the application of a correction for nonwax extractables is desired, a suitable unwaxed board specimen may be extracted and appropriate calculations made.