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American Hardboard Association

Today’s Hardboard TheThe Source Source This Introduction to Hardboard is designed to But did you know, for example, that hard- No other industry makes more complete use acquaint you with this most versatile of board is practically a 100% product of this great American natural resource. building materials. converted to fibers which are permanently Hardboard is made almost wholly from bonded under heat and pressure into wood and not just from logs or roundwood. You may be aware of some of the many hard- panel form? Wood chips and board trimmings, once board products around you. And perhaps wastes of the industry, are now rou- you have already worked with hardboard, to Or that hardboard products are available in tinely saved for processing into this most build a birdhouse or install a "storage wall" many forms other than familiar "brown versatile of home building materials. for above your . board" including sophisticated woodgrains and embossed surfaces for exterior and As well as efficiently utilizing the waste prod- interior uses? ucts of related industries, American Hardboard manufacturers main- Or that hardboard has superior physical tain and manage more than one million properties to most materials it has replaced, acres of forest land in soft and . and usually costs less? Look inside and learn many more interesting facts about Today's How hardboard is used. Hardboard. American hardboard manufacturers pro- duce more than 7-billion feet of Making wood even more hardboard every year, for a thousand-and- of a resource... one different products: from prefinished wall panelings to furniture components; "Waste no wood" makes good sense as a bat- from today's widest choice of factory-primed tle cry for all of us concerned with ecology. and factory-finished exterior sidings to a It is also a basic doctrine of hardboard pro- variety of utility boards for home and indus- duction in the U.S. today. try -solid and perforated.

From do-it-yourselfers to professional builders, Today's Hardboard is a "how to" material. It is the happy medium for people who make almost anything. How hardboard is made. Hardboard is made from wood chips con- verted to fibers which are permanently bond- ed under heat and pressure into a panel. The wood fibers are combined with natural and synthetic binders and other additives that improve certain properties. Different hardboards have different fiber formula- tions, accounting for characteristic variations in product density, thickness and finishing properties, for almost unlimited uses.

Hardboard, made from wood fibers, should not be confused with particleboard which is Official Definition... made from wood chips and particles which are not refined into a distinct fiber.

Hardboard is a generic term for a panel manufactured Particleboard production is a "dry" process. primarily from interfelted ligno- fibers consolidat- Hardboards, on the other hand, are pro- ed under heat and pressure in a hot press to a density of duced by both a "wet" or "dry" process. An at least 31 lbs. per cubic foot. The inter-fiber bond is pri- abbreviated and generalized description of marily achieved through the action of the mecha- both processes follows. nism. Other materials may be added during manufacture to improve certain properties, such as stiffness, hardness, finishing properties, resistance to abrasion and moisture, as well as to increase strength, durability and utility. The step-by-step story of hardboard

1. Removing bark change in pressure between the inside and hardboard. Multiple hydraulic presses are the outside of the chip causes it to explode heated by hot water, hot oil or steam. The Some hardboard manufacturers begin with into fiber bundles. This reduces the need combination of applied heat and pressure roundwood or logs. Others start “one step for further refining. welds the fibers back together and produces ahead” with mill wood residues (which properties unattainable in natural wood. need no “debarking”). Still others begin the The amount of press time, temperatures manufacturing process “two steps ahead” by 4. Refining and pressures vary widely, depending on the using prechipped wood from other sources. The softened chips are fed into refiners process and physical properties of the In all cases, the sequence is the same, where opposite rotating grinding disks board being produced. “Smooth one side” regardless of the locations in which these shred them into fibers. Small amounts of board is delivered to the presses on a wire preparatory processes occur. chemicals may be added at this stage to improve strength and impart improved mesh screen (hence the familiar “weave” moisture resistance to the finished product. pattern found on the reverse side of the “Barking” of logs is usually desirable to Fiber leaving the refiners is conveyed by air S1S hardboard). “Smooth two sides” board insure quality control and uniformity of or water depending on the type of forming (S2S) is hot-pressed between two smooth appearance in the finished product. It is that is used. plates. All boards emerge from the hot achieved either (1) mechanically by cutting presses with an extremely low moisture con- (2) hydraulically by high speed jets of water, 5. Forming hardboard tent. Some are next tempered-roll coated or (3) by tumbling logs together in a large, with oil, and baked at 290˚-340˚ F. The formation of felting of the fibers to rotating steel drum. Tempering increases hardboard's hardness, form a mat can be achieved by either a wet strength and water resistance. 2. Reduction and preparation or a dry process. Debarked roundwood or wood residues are 7. Humidifying The wet process employs a continuously next sent to the “chipper”, where they are To prevent -press warping or buckling, traveling mesh screen, onto which the reduced by whirling knives into uniform the boards are conveyed through a humidi- soupy flows rapidly and smoothly. chips about the size of a man's thumbnail. (A fier or stored on racks in a humidity cham- Water is drawn off through the screen and common chip size is 5/8" wide by 3/4" long.) ber. This raises the moisture content to then through a series of press rolls with approximate atmospheric humidity. wringing action similar to that of an old- Chips must be screened to prepare them Although hardboards are humidified, they fashioned washing machine. for defibration. Oversized chips are should be allowed to adjust to local atmos- returned for re-chipping. and other pheric conditions before being installed. fine particles are sifted and saved for use as In the dry felting process, comparatively dry fuel in the power plant. Acceptable chips fibers are laid out in much the same way 8. Trimming (ready for defibration) are conveyed to stor- but using air instead of a water medium. Tungsten carbide tipped trim boards to age bins. Nothing is wasted. Air-formed mats emerge much thicker and standard sizes. (True to the hardboard softer than wetformed ones, and require industry's “No Waste” philosophy, even these 3. Cooking more care in loading them into the press. trimmings are recycled for useful purpose.) Wood chips are cooked under heat and Sheets may be cut to any size a customer pressure to soften them and dissolve some 6. Pressing in hydraulic wants. Also, hardboard can be fabricated of the natural in the wood. This allows presses and finished in a variety of ways. the chips to be more easily reduced to From this point on, wet and dry process pro- After all operations and final inspection fibers in the refining process. In the “explo- duction procedures are virtually identical. have been completed, the boards are sion” method of digestion, the pressure is wrapped and sent to the warehouse for built up to high levels and then released Pressing under heat (380˚-550˚ F.) and pres- shipment to customers. through a quick release valve. The sudden sure (500-1500 P.S.I.) puts the “hard” in

The step-by-step story of hardboard

1. Removing bark 2. Reduction/ 3. Cooking 5. Forming hardboard 6. Pressing 7. Humidifying 8. Trimming preparation 4. Refining Hardboard: an extremely versatile material

It's . It's paneling. And things you'd never suspect!

Of the products shown here, how many had As a wood-base product, it follows that hard- Finishes can be applied in many ways: knife you already associated with hardboard? board can be sawed, routed, shaped and coat, roller coat, spray, curtain coat or dip. drilled with standard tools. Clear or pigmented finishes include stains, Durability, strength, surface smoothness, Indeed, because of its grainless uniformity penetrating sealer, shellac, latex base , superb machining and finishing qualities-all of texture, working with hardboard is usual- oil base paints, textured or water-thinned help account for hardboard's unique versa- ly easier than working with lumber. paints, lacquer, synthetics and wax. tility that helps make it the preferred base material for so many and diverse products. Hardboard can be securely glued or fas- No other material is so readily available in tened with screws, staples or nails. the range of wood-grain finishes, custom Hardboard is grainless, with uniform thick- Hardboard can also be laminated with plas- patterns and mix-or-match colors that hard- ness, density and appearance. It resists mar- tic films, high-pressure laminates and board users today take for granted. ring, scuffing, and abrasion, as well as veneers. It can even be bent, depending on changes in temperature and humidity. the type of board, thickness and the radius of curvature desired.

Hardboad: A Closer Look

The uses for hardboard are diverse. It can material to be used in more ways at less cost A knowledge of the meaning of hardboard, be used wherever a dense, hard panel mate- for application and finishing, and to permit its physical and mechanical properties, and rial in the thickness as manufactured will industrial users a saving in the final prod- an awareness of the influence of these prop- satisfy a performance or economical uct. By the selection of fiber content and erties on its performance characteristics are requirement better than any other material. advanced engineering and production tech- important to those persons specifying and niques, the industry's objective is to pro- working with hardboard. More and more effort is being expended by duce a hardboard that will meet and per- the industry to provide modifications and form for a specific end use. hardboard finishing that will permit the Hardboard: a closer look

Density and specific gravity under sudden localized load applied against the face of a panel held between supports. This value is usually determined by drop- Hardness ping a 2-inch diameter steel ball from increasing heights at the same point, the center, in the panel, until the panel fails. The height of drop in inches that produces (Density: weight per cubic foot.) (Hardness: testing for dent-resistance.) visible failure on the opposite face is record- Hardness is determined by the modified By formula, density is expressed as: ed as the index of resistance to impact. Density (lb/ft3) = Janka ball test: The load in pounds required to imbed a steel “ball” 0.444-inch in diame- Weight of sample (lbs.) x 12 Tensile strength ter to a depth of one-half its diameter, is the Area (ft2) x caliper of sample (in.) hardness value. When density is increased without any other changes, it tends to improve the following: a. Strength-improved bending, impact, (Pulling product apart laterally.) tensile, internal bond, stiffness and Abrasion screw holding properties. Tensile strength is the resistance of a material to being pulled apart laterally. The total b. Moisture resistance-An increase in den- applied force at the time of fracture (mea- sity reduces the rate at which moisture Abrasion resistance is resistance afforded by sured on a machine) is divided by the cross- can be absorbed. a material to wear by friction. AR is not nor- mally measured on unfinished hardboard, sectional area of the sample to give ultimate c. Hardness and resistance to abrasion. but can be determined by means of a Taber tensile strength in pounds per square inch. d. Machining qualities of edges and Abraser. This machine measures wear by Tensile strength = surfaces. standard filled wheels, and mea- Total Breaking Load A decrease in density tends to: sures resistance to scratching under a Width (in.) x Caliper (in.) a. Reduce weight, resulting in lower han- known load. The weight of the abrased sam- dling and shipping costs. ple is subtracted from the initial weight of b. Reduce manufacturing costs on hard- the sample to give the average weight loss in Internal bond strength boards of equal caliper. Less fiber and grams-per-number-of-cycles. resin are required. c. Improve nailing and stapling. Water absorption and thickness swelling Specific gravity is the ratio of the density of a material compared to the density of water. (Pulling product apart perpendicularly.) Specific Gravity = Bond strength is the force that it takes to pull Density of material (lb/ft3) a material apart in a direction perpendicu- Water absorption lar to its surface. Expressed in pounds per Density of water (lb/ft3) square inch, it is the force required to frac- 3 (a test for resistance to moisture) is the Approximate density of water = 62.5 lb/ft amount of water absorbed by a submerged ture a 2" x 2" specimen perpendicular to The density of hardboard is usually given as sample of hardboard in 24 hours. It is the surface: specific gravity for convenience of compari- expressed by “percentage weight increase,” Internal bond strength is an important proper- son with other materials. Because of its den- according to this formula: ty of hardboard. Products with high bond sity hardboard is harder than most natural Water Absorption (%) = strengths are manufactured for specific wood and because of its grainless character uses. Bond Strength = it has nearly equal properties in all direc- (Wet Weight-Initial Weight) x 100 Breaking load, lbs. tions in the of the board. It is not so Initial Weight stiff nor as strong as natural wood along the Thickness Swelling is the thickness increase 4 grain, but it is substantially stronger and (%) of a material after submersion in water stiffer than wood across the grain. for 24 hours. The caliper of the test sample Modulus of elasticity is measured before and after submersion, Modulus of rupture after which the figures are applied to this formula: % Swelling = (Wet Caliper-Initial Caliper) x 100 (Stiffness or resistance to bending.) Initial Caliper Modules of elasticity is a test of hardboard's Modulus of rupture, the ultimate unit Thickness swelling is critical where hard- ability to resist bending. It is determined by strength of a material in flexure or bend- board is subjected to large variations in applying a known concentrated load mid- ing, has become a common measurement humidity or long exposure to high humidity way between two supports and measuring of hardboard strength. Even though the fig- or water. the deflection that occurs. ME is then deter- ure obtained is not mathematically correct, mined by the following formula: ME = it is valuable in that it combines tensile, Total Load (lbs.) x Span3 (in.) compressive and bending properties. It is Impact 3 frequently used in comparing one material Strength 4 x Width (in.) x Caliper (in.) x Deflection (in.) with another. MOR = 3 x Total Breaking Load (lbs.) x span (in.) (Testing resistance to impact.) Impact Strength is resistance to fracture 2 x Width of Sample (in.) Caliper2 (in.) Classification of hardboard by thickness and physical properties

Tensile strength Water resistance Molulus of (max av per panel) (min av per panel) Class Nominal rupture thickness Water absorption Thickness (min av Parallel to Perpendicular based on weight swelling per panel) surface to surface inch percent percent psi psi psi 1/12 30 25 1/10 1 1/8 25 20 6000 3000 130 Tempered 3/16 1/4 20 15 5/16 15 10 3/8 10 9 1/12 40 30 1/10 2 1/8 35 25 4500 2200 90 Standard 3/16 1/4 25 20 5/16 20 15 3/8 15 10 1/8 35 30 3 3/16 30 30 Service- 1/4 30 25 4500 2000 75 Tempered 3/8 20 15 1/8 45 35 3/16 40 35 1/4 40 30 3/8 35 25 7/16 35 25 1/2 30 20 4 5/8 25 20 3000 1500 50 Service 11/16 25 20 3/4 13/16 7/8 20 15 1 1-1/8 1/4 50 30 3/8 40 25 7/16 40 25 1/2 35 25 5/8 30 20 5 11/16 30 20 2000 1000 25 Industrialite 3/4 13/16 7/8 25 20 1 1-1/8

Thickness tolerances for hardboard panels Nominal Thickness Thickness Range (min.-max.) Nominal Thickness Thickness Range (min.-max.) inch inch inch inch 1/12 (0.083) 0.070 -0.090 1/2 (.500) .475 - .525 1/10 (.100) .091 - .110 5/8 (.625) .600 - .650 1/8 (.125) .115 - .155 11/16 (.688) .660 - .710 3/16 (.188) .165 - .205 3/4 (.750) .725 - .775 1/4 (.250) .210 - .265 13/16(.812) .785 - .835 5/16 (.312) .290 - .335 7/8 (.875) .850 - .900 3/8 (.375) .350 - .400 1 (1.000) .975 - 1.025 7/16 (.438) .410 - .460 1 1/8 (1.125) 1.115 - 1.155 Physical Properties of Hardboard Siding

Property Requirement Thickness Water absorption, percent based on weight 12 (max av per panel) tolerances for Thickness swelling, percent 8 (max av per panel) Hardboard Siding Weatherability of substrate 20 (max percent residual swell) Nominal Thickness (min-max.) Weatherability of primed substrate No checking, erosion, flaking or objectionable fiber raising. Adhesion less than inch inch 0. 125 inch of coating "picked up" 1/4 (0.250) 0.220- 0.265 Thickness Maximum Linear 3/8 (0.375) 0.325- 0.375 Linear Expansion 30-90% RH range expansion 7/16 (0.438) 0.376- 0.450 (max percent) 0.220-0.324 0.36 1/2 (0.500) 0.451- 0.525 0.325-0.375 0.38 0.378-0.450 0.40 over 0.451 0.40

Nail-head pull-through, lb. 150 (min av per panel)

Lateral resistance, lb. 150 (min av per panel)

1800 for 3/8 & 7/16 & 1/2 inch thick Modulus of rupture, psi 3000 for 1/4 inch thick (min av per panel)

Hardness, lb. 450 (min av per panel)

Impact, In. 9 (min av per panel)

Moisture content, percent 4-9 incl., and not more than 3 percent variance between any two boards in any one shipment or order. Glossary of Terms Standard Grade–high strength and water Other Terms Decorative Overlaid–on which a film or resistance. Substantially same form as when sheet has been laminated; solid color, wood- it comes from press, except for humidifica- Patterned–has texture of pattern pressed, grain or other design. tion and trimming to size. punched or machined into surface; may be produced from basic hardboard. Core–for high-pressure decorative plastic Tempered Grade–impregnated with sicca- laminates, or for low-pressure plastic or tive material, stabilized by heat or processed Embossed–pattern impressed on one sur- veneer laminates. Characterized by good with special additives, to impart substantially face, such as simulated leather, wood-grain, perpendicular tensile strength, machinabili- improved properties of stiffness, strength, basket weave, etc. ty, smooth surface. Usually sanded for uni- hardness and resistance to water and abra- Grooved–uniform or random scoring or form thickness. sion, as compared with Standard. grooving. Die-Formed–hardboard molded between Service Grade–good strength, but somewhat Perforated–with factory-punched holes; may male and female dies. less strong than Standard. Substantially same be used for displays or to provide decorative Surface High Density–usually in density form as from press, except for humidifica- wall-mounted storage facility, or for acousti- ranges of 80-90 lb/cu. ft. Available in heav- tion and trimming size. cal purposes. ier thickness and in single or multiple plies Service-Tempered Grade–impregnated with Thickness–shown in accompanying tables. laminated with reinforced thermosetting siccative material, stabilized by heat or bond. Usually S2S and treated for special Face Dimensions–panels generally are 4 and processed with special additives, to impart electrical and machining properties. 5 ft. wide. Lengths are generally up to 16 ft. substantially improved properties of stiffness, Generally has hard surface, low water strength, hardness and resistance to water Other Commercial Products absorption, high modulus of rupture. and abrasion, as compared with Service. Lap Siding–after installation, yields a pattern Laminated–using an between mul- Industrialite Grade (Medium Density of horizontal planks. This siding may be tiple plies to obtain greater thickness. Hardboard)–moderate strength, lower unit embossed, grooved, and/or smooth on the weight than other types. Primed or Coated–with or other coat- face. Normally available in strips 16 feet long. ing applied to discernible film thickness for Smooth-one-side (S1S)–with impression of Panel Siding–after installation, yields a flush decorative purpose or as base for further screen on one side. surface. This siding may be either finishing. Smooth-two-sides (S2S)–produced from sub- embossed, grooved, and/or smooth on the Factory-Sealed (or Factory-Filled)–with seal- stantially dry fiber mat pressed between two face. Panels normally available sized 4 feet er (or filler) incorporated in board surface smooth platens. by 8 feet. for improved smoothness, finishing charac- teristics and/or decorative purposes. Publications AHA list of publications includes the following:

* Today's Hardboard ANSI Standard ANSI/AHA A135.4

* Recommended Basic Application Basic Hardboard-$4.00 and Painting Instructions for ANSI Standard ANSI/AHA A135.5 Hardboard Siding Hardboard Paneling-$4.00 * Maintenance Tips for Hardboard Siding ANSI Standard ANSI/AHA A135.6 * Basic Hardboard Products Hardboard Siding-$6.00

About The American Hardboard Association

The American Hardboard Association is the national trade organization repre- senting manufacturers of hardboard products used for exterior siding, interior wall paneling, household and commercial furniture, and industrial and com- mercial products. AHA serves as the central clearing house on industry and technical information for architects, builders, contractors, distributors, dealers, government agencies and the general public. The Association is concerned with statistical reports, standard/specification programs, research activities, building codes, environmental affairs, educational publications, manufacturing and safety activities and governmental relations. The Association also adminis- ters a quality conformance program for hardboard siding.

For additional information and literature, contact: American Hardboard Members: Association ABTco Inc. Stimson Lumber Company 1210 W. Northwest Highway 10115 Kincey Ave., Suite 150 Hardboard Operations Palatine, Illinois 60067 Huntersville, NC 28078 P.O. Box 68 Telephone: (847) 934-8800 Telephone: (800) 566-2282 Forest Grove, Oregon 97116 Fax: (847) 934-8803 Fax: (704) 875-1680 Telephone: (503) 357-2131 Email: aha hardboard.org @ Fax: (503) 359-3400 www.hardboard.org Collins Products LLC P.O. Box 16 Temple Klamath Falls, Oregon 97601 P.O. Drawer N Telephone: (800) 417-3674 Diboll, Texas 75941 Fax: (541) 884-7282 Telephone: (936) 829-5511 Fax: (936) 829-1730 Corporation One South Wacker Drive Chicago, Illinois 60606 Telephone: (312) 750-0900 Fax: (312) 750-1233

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