Fiberboards - 2869 



tempered and then sanded on the back side to assure thickness control. Some 

 embossed boards are overlaid with printed paper mated to the textured surface; 

 most, however, are printed only on the high spots. 



Molding. — Dry-formed fiber mats can be molded during pressing (fig. 23-95 

 bottom) into corrugated panels or into door surfaces that simulate frame and 

 panel construction. Flat sheets formed either wet or dry can be molded after 

 pressing, but to a much lesser depth of draw. 



HARDBOARD FINISHING 



Finishing is a significant, capital- and energy-intensive phase of manufactur- 

 ing hardboard siding, decorative board, and paneling. The ratio of finished to 

 unfinished board can be as high as 9 to 1 in some operations. The finishing 

 department may be an extension of the board manufacturing process, or inde- 

 pendent and serving more than one board manufacturing plant. Categories of 

 finished hardboard products are as follows: 



• Interior paneling is typically printed with wood grain and grooved for 

 plank appearance, or embossed and painted to simulate brick or stone 

 walls. The substrate is usually !/4-inch SIS board with specific gravity of 

 about 0.73. The ^A-inch thickness provides stiffness needed when the 

 panels are mounted directly on 2- by 4-inch stud walls without the added 

 support of gypsum-board dry wall. Wall paneling '/s-inch thick is made at 

 higher densities. 



• Decorative board is paneling — normally not grooved — finished in solid 

 colors or printed with designs other than wood grain. Such paneling 

 includes vinyl overlaid boards with wall paper appearance, and tile 

 boards — the latter used on bathroom walls and as shower enclosures, a 

 demanding application. Light solid colors and high-gloss surfaces pre- 

 clude use of SIS substrates because their screen backs release particles 

 onto the wet finish; S2S substrates are therefore used. A board thickness 

 of !/8-inch is sufficient, since decorative boards are generally applied 

 over gypsum dry wall. 



• Siding is manufactured for application as panels or as lap siding. It can be 

 smooth, or embossed to simulate rough-cut lumber. Siding boards are 

 7/16-inch thick and of relatively low density (about 1,500 pounds per 

 thousand square feet). Both SIS and S2S hardboards are used. 



Embossed boards for paneling and siding require base coat application with a 

 pile roll to reach into embossed crevices; these applicator rolls are covered with 

 a sleeve of soft material similar to pile carpeting. For two-tone effects, the high 

 spots are then coated with the smooth roll of a precision roll coater (fig. 23-96). 

 Embossed boards can usually tolerate more surface imperfections because de- 

 fects are obscured by the embossed profile. 



Finishing materials. — All hardboard finishes have three principal 

 components: 



• Resin or binder develops necessary adhesive and cohesive forces to 

 form the film and bond it to the substrate, controlling water resistance. 



