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CHAPTER 16 Manufactured Panel Products

Objectives Panel products are typically more stable than solid lumber. They warp less because they are con- After studying this chapter, you should beableto: structed with layers of thin wood or wood fibers. • Describe the materials found in each category There is no continuous grain pattern in a panel. This of manufactured panel products. keeps distortion to a minimum. Some panels are • List the methods used to grade panel products. even moisture resistant. • Explain the advantages of various panel The faces may be rough, textured, smooth, or products for cabinets and fine furniture. finished. See Figure 16-1. The appearance of higher grades is suitable for clear finish. Lower grades contain defects. Veneered panels look like solid-wood Technical Terms appearance panels oriented strand board composite panel (OSB) engineered wood particleboard products performance-rated face veneer structural wood panel fiberboard phenolic resin group number plywood hardboard prefinished plywood panel hardwood plywood prehung wallpaper high-density fiberboard paneling (HDF) simulated wood grain industrial particleboard finish panels low-density fiberboard structural particleboard (LDF) structural plywood lumber-core plywood structural wood panels medium-density fiberboard (MDF) veneer-core plywood Mende particleboard veneer grade waferboard

Manufactured panel products are widely used by cabinetmakers to create large surfaces for case goods. They reduce the need for edge gluing lumber Oleg-F/Shutterstock.com to make wide boards. Production time is reduced Figure 16-1. Wood panels offer many textures and without sacrificing quality. appearances.

/ 234 Section 3 Materials lumber. Those made of wood chips or fibers do not screws can be inserted close to edges without split- resemble real wood. Selection is based on whether ting the panel. the panel is to be hidden or visible. Structural plywood is manufactured from soft- The edges of veneered and nonveneered panel wood. Hardwood plywood has hardwood veneer products reveal their composition. Edges are either over a hardwood or softwood core. Although struc- hidden in the joint or covered with wood tape, plas- turally sound for cabinetry, hardwood plywood is tic strips, or edging. considered an appearance product. There are three categories of panel products. The core for structural plywood varies according These products are structural wood panels, appear- to use. The two most common cores are veneer and ance panels, and engineered board products. lumber.

Veneer-Core Plywood 16.1 Structural Wood Panels Veneer-core plywood is plywood constructed using a core of an odd number of plies, with face and Structural wood panels are selected when sta- back veneers or overlays bonded together with adhe- bility and strength are required. They are typically sive. The number of veneer layers used depends on used for roof, wall, and floor sheathing for building the desired properties of the completed panel. The construction and for cabinetmaking when the prod- thickness of the veneers and the quantity of plies uct requires more stability than beauty. Lamina- used determine the total panel thickness. The veneer tions, such as printed vinyl or high-quality veneer, thickness may vary from 1/50″ to 1/4″ (0.5 mm to enhance the appearance. 6 mm). Thinner veneers become face layers while Structural wood panels are manufactured in var- thicker veneers may make up core plies. Alternat- ious ways. Veneer-core plywood is made by bonding ing the grain direction of successive layers increases layers of wood veneer with adhesive. Waferboard, strength and reduces warpage. composite board, structural particleboard, and ori- Panel thickness of veneer-core plywood ranges ented strand board are all made of wood chips or from 1/8″ to 1 3/16″ (3 mm to 30 mm). Common fibers bonded under heat and pressure. thicknesses range from 1/4″ to 3/4″ (6 mm to 19 mm). Three-layer, or three-ply, panels are made with two 16.1.1 Plywood veneer layers and one core layer. Three-ply panels are usually 1/4″ (6 mm) thick. Front and back faces Plywood is the most common structural panel. are bonded to a single core. SeeFigure 16-3. Five-ply It is manufactured with a core material sandwiched panels have two faces and three cores. They are used between two thin wood sheets, called face veneers. for panels from 5/16″ to 1/2″ (8 mm to 13 mm). Seven The core veneers (all veneer layers between the plies are used for panels up to 3/4″ (19 mm) and nine outside face veneers) are cut on a lathe. This pro- plies are used for thicker panels. The most popular cess involves rotating a debarked log (a peeler block) panel size is 4′ × 8′ (1220 mm × 2440 mm). Smaller against a knife. The veneer is sheared from the log in and larger sizes are available. long sheets that are cut to size. The sheets are sorted Veneer-core plywood is much less expensive according to quality. Defects may be patched later. than lumber core. It also has greater structural value. SeeFigure 16-2. Select veneer plywood when the appearance of the Face veneers are sheets applied over the core edge is not a concern. Veneer-core edges may show material. The core may be lumber, particleboard, or core voids and defects. veneer plies. Glue is applied to the layers, which are Plywood with hardwood face veneers is avail- then clamped under heat and pressure until cured. able with as many as five plies in a 1/8″ (3 mm) thick The panel is then trimmed to size and shipped. panel. American, Finnish, and Russian plywood Pound for pound, plywood is stronger than steel. panels are available with a greater number of plies Unlike solid wood, which is strong along the grain per given thickness than those described in the pre- and weak across the grain, plywood is strong in all vious paragraph. For example, the following sizes directions. The grain direction is rotated 90° for each are available: successive layer of wood, with the grain of both face • Three plies—3 mm (1/8″). veneers oriented in the same direction. These two properties strengthen the panel and equalize ten- • Five plies—6 mm (1/4″). sion from the grain direction. They also give ply- • Seven plies—9 mm (3/8″). wood its resistance to checks and splits. Nails and • Nine plies—12 mm (1/2″).

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• 11 plies—15 mm (5/8″). ers between the core and the back and front faces. • 13 plies—18 mm (3/4″). These are called cross-bands. See Figure 16-4. The cross-band grain is at 90° to the faces. Thicker pan- The core materials have virtually no voids, els are obtained with two lumber cores separated by allowing the edges to be left exposed. American a cross-band. Standard panel size is 4′ × 8′ (1220mm manufacturers will produce these veneer cores in × 2440 mm). Thicknesses can range from 5/8″ to 2″ any popular species. However, maple is the species (15.5mm to 50 mm). normally stocked by distributors. The Finnish and Lumber-core plywood is chosen when solid Russian products are birch. edges are important: Thin veneer, three-ply birch veneer cores, are • On exposed edges. The cut edges of lumber- available in the following thicknesses: 1/64″ (0.4mm), core plywood are solid. 1/32″ (0.8 mm), 3/64″ (1 mm), and 1/16″ (1.5 mm). Versions with five plies are available in thicknesses • On edges that contain jointwork. Machined of 5/64″ (2 mm), 3/32″ (2.5 mm), 1/8″ (3 mm), and edges of lumber-core plywood are solid wood. 5/32″ (4 mm). A nine-ply version is 13/64″ (5 mm). • When hardware will be attached. Lumber core has excellent edge screw-holding properties. Lumber-Core Plywood Lumber-core plywood has a solid wood center and thin veneer faces. The core may be thin, laminated strips of wood or wider boards. There are veneer lay-

3-Ply Core Faces

5-Ply with Core Edge Banding Faces Core Cross-bands Faces

Faces 5-Ply with Cross-bands Laminated Core Laminated core Core Cross-bands Faces Core

5-Ply with 7-Ply, lumber core and railing Two Core Cross-bands

Faces Faces Rails 5-Ply core Core Cross-bands

Goodheart-Willcox Publisher Forest Products Laboratory Figure 16-3. An illustration of veneer-core plywood Figure 16-4. Lumber-core plywood includes layers of showing three-, five-, and seven-ply versions. solid wood and veneer. Banding may be applied to hide edges. Panels with rails permit machining the edges.

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Green Note

Agrifiber products such as wheat, straw, and rice hulls are left behind after harvesting. This residue is often burned, resulting in the release of CO2. Agrifiber provides an alternative to composite based products such as plywood, particleboard, and MDF. It can be used to make cores for doors, as well as panels for cabinets and construction materials.

Particleboard Particleboard is an engineered wood panel composed of small wood flakes, chips, and shavings, bonded together with resin or adhesives. It is the APA—The Engineered Wood Association most stable and least expensive material. However, Figure 16-5. Plywood is stamped with a grade the edges offer poor screw-holding capability. Core trademark from APA—The Engineered Wood Association. The mark provides information on the wood construction can be seen on the edges, but these are species, quality, and recommended use. usually hidden with wood tape. It is approximately the same price as veneer-core plywood, but much less expensive than lumber-core plywood.

Surface Smoothness Standards are established by manufacturers’ The face veneers of plywood may be smoothed. associations such as APA—The Engineered Wood The panel may be sanded on one side (S1S)or both Association and the Hardwood Plywood and Veneer sides (S2S). They may also be touch sanded or fully Association (HPVA). Governmental specifications sanded. When touch sanded, only the rough sec- are made by the National Institute of Standards and tions and wood splinters are removed. Fully sanded Technology (NIST). panels are prepared for finish, but should be lightly The group number in the grade stamp indi- sanded before finish is applied. cates the weakest species used for face veneers. For sanded panels, the group number indicates the exact US Structural Plywood Grades species group. Group 1 contains the strongest and stiffest woods. See Figure 16-6. Structural plywood can be graded for performance or nonperformance. Performance grades The quality of the two faces is given as a veneer classify veneer and nonveneer panels for the con- grade, which refers to the number of defects and the methods by which they are patched. The grades struction industry. They are designed to meet requirements for spanning roof or floor joists. are indicated by letters separated by a hyphen, These grades are discussed later in the chapter. Figure 16-7. For example, a piece of A-C plywood Most plywood applications do not require the means the grade of the front face veneer is A and strength of performance-grade panels. Nonperfor- the grade of the back face veneer is C. If only the mance plywood grades focus mostly on defects. front face will be seen, you might choose an N grade However, they do meet standard strength require- as the front face and a C or D grade as the back face. The recommended environment where the ments. The grade is stamped either on the face or the edge of the plywood panel. SeeFigure 16-5. This panel is used is indicated by either INT (interior) stamp provides important information about the: or EXT (exterior). • Type of wood species of the front and back faces. Canadian Structural Plywood Grades • Quality of the faces. Canadian structural plywood is manufactured according to rules set by the Canadian Standards • Type of adhesive used to bond the plies. Association (CSA). Panels must meet CSA standards • Manufacturer of the product. to be certified by the Council of Forest Industries of • Mill number. British Columbia (COFI).

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Species Group Classification

Group 1 Group 2 Group 3 Group 4 Group 5

Apitong Cedar, Port Orford Maple, Black Alder, Red Aspen Basswood Beech, American Cypress Mengkulang Birch, Paper Bigtooth Poplar, Balsam Birch Douglas Fir 2 Meranti, Red Cedar, Alaska Quaking Sweet Fir Mersawa Fir, Subalpine Cativo Yellow California Red Pine Hemlock, Eastern Cedar Douglas Fir 1 Grand Pond Maple, Bigleaf Incense Kapur Noble Red Pine Western Red Keruing Pacific Silver Virginia Jack Cottonwood Larch, Western White Western White Lodgepole Eastern Maple, Sugar Hemlock, Western Spruce Ponderosa Black (Western Pine Lauan Black Spruce Poplar) Caribbean Almon Red Redwood Pine Ocote Bagtikan Sitka Spruce Eastern White Pine, Southern Mayapis Sweetgum Englemann Sugar Lablolly Red Lauan Tamarack White Longleaf Tangile Yellow-Poplar Shortleaf White Lauan Slash Tanoak

APA—The Engineered Wood Association Figure 16-6. Species used for face veneers of plywood are grouped according to their strength. Group 5 contains the weakest species.

Veneer Grades N Smooth surface ″natural finish″ veneer. Select, all heartwood or all sapwood. Free of open defects. Allows not more that 6 repairs, wood only, per 4 × 8 panel, made parallel to grain and well-matched for grain and color. A Smooth, paintable. Not more that 18 neatly made repairs, boat, sled, or router type, and parallel to grain, permitted. Some minor splits permitted. B Solid surface. Shims, sled or router repairs, and tight knots to 1 inch across grain permitted. Wood or synthetic repairs permitted. Some minor splits permitted. C Improved C veneer with splits limited to 1/8-inch width and knot holes or other open defects limited to 1/4 × 1/2 inch. Wood or synthetic repairs permitted. Admits some broken grain. Plugged C Tight knots to 1-1/2 inch. Knotholes to 1 inch across grain and some to 1-1/2 inch if total width of knots and knotholes is within specified limits. Synthetic or wood repairs. Discoloration and sanding defects that do not impair strength permitted. Limited splits allowed. Stitching permitted. D Knots and knotholes to 2-1/2 inch width across grain and 1/2 inch larger within specified limits. Lim- ited splits are permitted. Stitching permitted. Limited to Exposure 1.

APA—The Engineered Wood Association Figure 16-7. Face veneers are graded by wood characteristics such as knots and splits. Some defects are patched.

The CSA has adopted the metric system for siz- 400 mm centers. The 1200 mm × 2400 mm panels fit ing panel products. Sizes are comparable to those the new standards. The 1220 mm × 2440 mm pan- of US grades. See Figure 16-8. Most existing struc- els are made for use in structures based on the old tures in Canada were constructed with standards system. similar to those of the United States. Studs were The COFI certification mark contains infor- 16″ (406 mm) on center. Now they are installed on mation necessary when selecting the panel. See

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Sizes and Thicknesses Figure 16-9. The species designation refers to one of CANPLY Exterior Plywood of the two species groups used in COFI plywood: Douglas fir plywood (DFP) or Canadian softwood Thickness Size plywood (CSP). See Figure 16-10. The COFI mark Sanded Grades Sheathing and also indicates mill and CSA standard governing Select Grades manufacture. The COFI mark does not indicate Lengths the veneer-ply grade. It is simply an assurance to 6 mm 19 mm 7.5 mm 20.5 mm Available up the buyer that the plywood meets CSA standards. 8 mm 21 mm 9.5 mm 22.5 mm to 2500 mm 11 mm 24 mm 11 mm 25.5 mm The standards ensure that the panel will perform 14 mm 27 mm 12.5 mm 28.5 mm in a satisfactory and predictable manner. Widths 17 mm 30 mm 15.5 mm 31.5 mm Veneer-ply grades designate the face, back, Available 18.5 mm 30 mm and inner plies. They also note the type of defects from in the panel. The face and back veneers may be All thicknesses are metric, but some 600 mm to sanded, unsanded, or covered with resin-fiber approximate imperial dimensions, 1250 mm e.g. 6 mm (1/4in.) overlay, Figure 16-11.

CANPLY—Canadian Plywood Association Figure 16-8. The CSA adopted the metric system for plywood dimensions in 1978.

Face Stamp on CANPLY EXTERIORPlywood (Unsanded grades)

www.canply .org

Edge Stamp on CANPLY EXTERIORPlywood (Sanded and Unsanded grades)

PLYCO CANADA BC xxx CANPLY EXTERIOR CSP GRADE

INTERNATIONAL CERTIFICATION MARKS:

CANPLY—Canadian Plywood Association Figure 16-9. COFI plywood grade stamp contains information on wood species, glue bond, and CSA standard.

/ 240 Section 3 Materials

Species Permitted in CANPLY Exterior Plywood

Douglas Fir Plywood Canadian Softwood Plywood

Common Name Faces & Backs Inner Plies Faces & Backs Inner Plies Douglas Fir • • • True fir* • • • Western white spruce* • • • Sitka spruce* • • • Lodgepole pine* • • • Western hemlock* • • • Western larch* • • • Trembling aspen • • White birch • • • Balsam fir • • • Eastern spruce • • • Eastern white pine • • • Red pine • • • Jack pine • • • Ponderosa pine • • • Western white pine • • • Eastern hemlock • • • Tamarack • • • Yellow cedar • • • Western red cedar • • Balsam poplar • • Black cottonwood • • *Permitteodn the backs of 6, 8, 11 and 14 mm Good One Side DFP CANPLY—Canadian Plywood Association Figure 16-10. Canadian plywood is divided by species into two areas. Inner plies contain the same species for both DFP and CSP.

Adhesives flexible, and provides an excellent bond. It is often called urea-formaldehyde resin. The adhesive that bonds the layers determines, Formaldehyde is added to the resin to speed in part, how the plywood is used. curing time. However, formaldehyde gas is an • Type I fully waterproof adhesives. Used for eye and respiratory irritant. The US exterior plywood. Type I panels are used for Environmental Protection Agency (EPA) has siding and sheathing. They are installed in recommended that lower levels of formalde- other areas exposed to excessive moisture and hyde be used to prevent outgassing. Interior microorganisms. Type I adhesives include plywood bonded with exterior glue is recom- melamine-resin, phenolic-resin, and resorcinol- mended. The face veneers are interior quality, resin. yet safer glues are used for bonding. • Type II moisture-resistant adhesives. Used for • Type III moisture-resistant adhesives. They interior plywood grades. The bond retains its retain their strength only if occasionally strength when occasionally exposed to wetting subjected to moisture. Thorough wetting of the and drying. Interior plywood is installed where plywood will cause separations of the layers. the moisture content will not exceed 20%. Type III panels are used for industrial applica- • Urea resin. The most widely used interior tions such as crating panels and upholstered plywood adhesive. It is inexpensive, extremely furniture blanks.

/ Chapter 16 Manufactured Panel Products 241

CANPLY Exterior Plywood Grades

Veneer Grades** Grade* Product** Inner Characteristics Typical Applications Face Back Plies Good Two Sides DFP A C A Sanded. Best appear- Furniture, cabinet doors, (G2S) ance both faces. May partitions, shelving, contain neat wood concrete forms and Sanded Poplar patches, inlays or opaque paint finishes. synthetic patching material. Good One Side DFP A C C Sanded. Best appear- Where appearance (G1S) ance one side only. or smooth sanded May contain neat surface of one face is wood patches, inlays important. Cabinets, or synthetic patching shelving, concrete material. forms. Select - Tight Face DFP B*** C C Surface openings shall Underlayment and (SEL TF) be filled and may be combined subfloor and lighted sanded. underlayment. Hoard- ing. Construction use Select (SEL) DFP Aspen B C C Surface openings shall where sanded material Poplar CSP be filled and may be is not required. lighted sanded. Sheathing (SHG) DFP Aspen C C C Unsanded. Face may Roof, wall and floor Poplar CSP contain limited size sheathing. Hoarding. knots, knotholes and Packaging. Construc- other minor defects. tion use where sanded material is not required. High Density DFP Aspen B*** C B*** Smooth, resin-fiber Bins, tanks, boats, fur- Overlaid (HDO) Poplar CSP overlaid surface. niture, signs, displays, Further finishing not forms for architectural required concrete. Medium Density DFP Aspen C*** C C Smooth, resin-fiber Siding, soffits, panel- Overlaid (MDO) Poplar CSP overlaid surface. Best ing, built-in fitments, MDO 1 Side paint base. signs,any use requiring a superior paint MDO 2 Sides DFP Aspen C*** C C*** surface. Poplar CSP *Allgrades and products including overlays bonded with waterproof resin glue. **Forcomplete veneer and panel grade descriptions see CSA O121 (DFP), CSA O151 (CSP) and CSA O153 (Popular). ***Indicateasll openings are filled. CANPLY—Canadian Plywood Association Figure 16-11. Using various veneer-grade combinations, Canadian manufacturers produce panels for a variety of uses.

16.1.2 Composite Panel 16.1.3 Waferboard A composite panel consists of wood chip or Waferboard is made of wood wafers and resin fiber core faced with a veneer. See Figure 16-12. In adhesive, Figure 16-12. Wood wafers are high-qual- addition to veneer, printed vinyl and paper are used. ity chips of wood approximately 1″ to 2″ long and Composite panels are used in both construction and of varying widths. The adhesive is generally a phe- cabinetmaking. Lower grades serve as floor under- nolic resin-based product. Phenolic resin is a ther- layment as well as roof or wall sheathing. Grades mosetting resin of high mechanical strength that is suitable for finishing are installed as wall paneling generally resistant to water, acid, and resin solvents. or used for frame and panel cabinetry. Panels designed for interior use are fabricated with

/ 242 Section 3 Materials

Type III adhesives. The chips and adhesive are mixed Particleboard is typically found in 48″ × 96″ and then formed into panels with heat and pressure. (1220 mm × 2440 mm) sheets. Larger sizes are avail- Edges are trimmed to square the waferboard. able. Thickness varies from 1/4″ to 2 1/4″ (6 mm to Waferboard faces often differ. One side might be 57 mm). smooth and slick. The other could have a screenlike texture. The textured side is suitable for veneer or printed plastic laminations. 16.1.5 Oriented Strand Board Oriented strand board (OSB) is manufactured 16.1.4 Structural Particleboard with strands of wood that are layered perpendicu- lar to each other. OSB is a cross between waferboard Structural particleboard, often called flake- and plywood. Like plywood, layers are in alternat- board, is composed of small wood flakes, chips, and ing directions. However, layers are high-quality shavings bonded together with resins or adhesives. wood chips, not veneer. OSB is similar to wafer- See Figure 16-12. Particleboard is manufactured board, except that chips are arranged in a pattern, much like waferboard. However, the wood chips are not randomly. Refer again to Figure 16-12. Three much smaller. The chips are mixed with glue, then layers of chips are bonded with phenolic resin under pressed into panels. heat and pressure. Structural particleboard is specially made to OSB ranges in thickness from 1/4″ to 23/32″ withstand the stress and environment required for (6 mm to 18 mm). Thinner sheets have many applica- building materials. A common application is floor tions, such as dividers, shelving, and cabinet backs. underlayment. Higher density layers on the sur- Sheets from 3/8″ to 1/2″ (10 mm to 13 mm) serve faces contain smaller wood chips, extra resin, and as roof deck, wall, and subfloor sheathing. Sheets wax. The increased density gives the panel greater thicker than 1/2″ (13 mm) are used for single-layer strength and water repellency. flooring. OSB has excellent dimensional stability and stiffness. It is frequently sanded smooth on both sides unless used for roof sheathing. One side is given a textured, skid-resistant surface. When processing OSB, carbide-tipped blades are necessary. The high Plywood density of the board will quickly dull noncarbide blades.

16.1.6 Performance Ratings Waferboard Performance-rated structural wood panels are designed to span specified distances. Applications include flooring, roof sheathing, and other building Composite panel construction. Any structural wood panels may be performance rated, if they pass test standards. These must meet or exceed US product standards. Standards met by performance-rated panels Structural particleboard require rigid control of strength properties, dimensional stability, and bond durability. These are affected by the following: Oriented • Wood species used to manufacture the panel. strand board • Size, shape, and orientation of wood particles (for nonveneer panels). • Board density. • Adhesive type.

Georgia-Pacific Corp. The performance rating is stamped on the panel. Figure 16-12. Structural wood panels are selected for It indicates certification met through testing desig- stability and strength. They are used in many building nated by the Engineered Wood Association. construction applications.

/ Chapter 16 Manufactured Panel Products 243 16.2 Appearance Panels Manufacturers select hardwood plywood for many purposes. These include cabinets, furniture, Appearance panels may replace lumber in cabi- and wall paneling. There is a wide selection of thick- nets and furniture. They are fabricated to match nesses, veneers, species, and grades. the grain pattern of a particular wood species. The texture may be smooth or patterned. Most modern Face Veneer cabinet construction is done with unfinished hard- The face veneers of hardwood plywood may wood plywood panels. They provide the appearance be cut from a number of wood species. Ash, birch, and strength of solid hardwood, yet are much less cherry, elm, gum, mahogany, maple, oak, hick- expensive. ory, rosewood, teak, and walnut are common. The Other appearance panels are used primarily as appearance is determined by the following: wall covering. They include: • Species. • Prefinished hardwood- and softwood-veneered plywood. • Portion of the tree from which veneer was cut. • Simulated wood grain finish on plywood. • Method of cut. • Simulated wood grain finish on wood-fiber • Method of matching. substrate. These topics will be discussed in the next chapter. • Prehung wallpaper paneling. Core Construction Hardwood plywood cores may be veneer, lum- 16.2.1 Hardwood Plywood ber, particleboard, or fiberboard. Some cores are Manufacturers of hardwood plywood concentrate combinations of veneer and particleboard. Specialty on appearance-grade plywoods. See Figure 16-13. cores include acoustical, fire-resistant, and light- The panels have hardwood face veneers over lumber, weight materials. veneer, particleboard, or specialty cores. Hardwood • Fiberboard cores have a denser core than parti- plywood is manufactured much the same as soft- cleboard cores. The edges can be easily wood. Both use similar cores and adhesives. Hard- machined and closely resemble real wood wood plywood differs in the way face veneers are cut when left exposed. and arranged. The face veneers are matched to create • Acoustical cores deaden sound transmission. a desired appearance. Many acoustical panels are suitable for veneer lamination. • Fire-resistant cores are chemically impregnated or made with mineral materials to resist fire. • Lightweight cores make use of lightweight materials and the honeycomb structure used by bees. Honeycomb cores have large strength to weight ratios. Typical core materials include kraft paper and aluminum. Other lightweight cores are made of wood coils and grids.

Thickness The most popular thicknesses in hardwood plywood are 1/4″ (6 mm) and 3/4″ (19 mm). Thicker plywood is for casework. Thinner sheets are for backs and drawer bottoms. You can buy 3/8″ (10 mm) panels. However, these panels are made with top-grade veneer and are more expensive.

jocic/Shutterstock.com Hardwood Plywood Grading Figure 16-13. Hardwood plywood is fabricated with hardwood face veneers, for use where appearance is Standards for hardwood plywood are set by important. the HPVA. The grade is established by the quality

/ 244 Section 3 Materials of the two face veneers. Face veneers are graded method of matching the veneer may also be by the number of defects. The best veneer has few specified. Specialty plywoods are ordered for defects. The worst can contain many defects. See architectural purposes. The grade is usually Figure 16-14. stamped on the edge of the panel. • Specialty hardwood plywoods refer to special • Premium A-1 and Premium A-2 are the finest orders between manufacturers and purchasers. stock grades of hardwood plywood. Premium- Special cuts of veneer can be ordered. The grade veneer is applied to the front face and to the back face, Figure 16-15. The grading range for faces goes from AA to E. Standard Surfaced Thicknesses • The back veneer is usually the same wood Face Quality General Description species as the front, but has some defects. The Grade grading range for backs goes from 1 to 4. AA A premium face grade for exclu- Unless specified, a veneer core of any species of sive uses such as architectural wood will be used. It may not be entirely paneling and interiors, case sound inner plies frequently have knotholes goods, and quality furniture. that show as voids in edges of cut panels. Voids A Suitable for areas where AA is can be filled with wood putty or plugged. not required but excellent • Shop grades are assigned to panels that do not appearance is still important. meet the grading criteria. These panels have B Used where natural characteris- often been damaged in transport or have tics and appearance of the manufacturing defects. To qualify as Shop Best to species are desirable. grade, they must have 80% usable surface area. Worst C Allows for unlimited color and Any grade combination of face and back increased natural characteristics. veneers can be obtained for hardwood plywood. Perfect for applications where See Figure 16-16. Dealer stocks are often limited, and economical panel is needed. but specialty orders can be made. D and E Provide sound surfaces but allow unlimited color variation allow repairs in increasing size ranges. 16.2.2 Ordering Hardwood Recommended uses: areas where surface will be hidden or a Plywood more rustic character is desired. The types of plywood stocked by lumber dealers Back varies according to region. A variety of cores, veneer General Description Grade species, veneer cuts, and veneer matches are available. Check with your supplier for the panels they 1 Grades 1 and 2 provide sound have or can order. When ordering, include the fol- surfaces with all openings in the 2 veneer repaired except for verti- lowing specifications: cal worm holes not larger than • Number of panels (not square or board feet). 1/16″ (1.6 mm). • Width, length, and thickness. 3 Grades 3 and 4 permit some • Number of plies (for veneer core if choice is Best to open defects provided they are given). Worst 4 repaired to achieve a sound • Core construction (if other than veneer). surface. These include splits, joints, bark pockets, laps, and • Species of front face veneer. knot holes. Grade 4 permits knot • Method used to cut front face veneer (if choice holes up to 4″ (102 mm) in diam- is given). eter and open splits and joints • Method of matching front face veneer (if choice limited by width and length. is given). Hardwood Plywood Handbook • Grade (if grade is G1S, specify wood species of Figure 16-14. Hardwood plywoods are specified back veneer). according to the ANSI/HPVA HP-1 standards. Faces use a number system and backs use a letter system. Grades • Adhesive type. are species dependent. The above chart is a broad overview of the grades used.

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FACE GRADE CHARACTERISTICS: RED AND WHTE OAK (Plain Sliced, Quarter-Cut, Rift and Comb Grain, Rotary Cut), According to ANSI/HPVA HP-1 2009 © Table 3.3

Natural Characteristics (Except as limited below, Natural characteristics are not restricted)

Grade AA Grade A Grade B Grade C Grade D Grade E Grade Description Small Conspicuous Burls 8 per 4 × 8′ 12 per 4 × 8′ 24 per 4 × 8′ No limit No limit No limit and Pin Knots—Comb. panel panel panel Avg. Number Conspicuous Burls— 1/4″ 3/8″ 1/2″ No limit No limit No limit Max. Size Conspicuous Pin Knots No 1 per 3 sq ft 1 per 2 sq ft No limit No limit No limit Average No 10 per 4 × 8′ 16 per 4 × 8′ Number panel panel Max. Size: Dark Part N/A 1/8″ 1/8″ Max. Size: Total N/A 1/4″ 1/4″ Scattered Sound and 1 per 8 sq ft 1 per 4 sq ft 1 per 3 sq ft 1 per 4 sq ft Repaired Knots Combined Average 4 per 4 × 8′ 8 per 4 × 8′ 10 per 4 × 8′ 8 per 4 × 8′ Number panel panel panel panel

Max. Size—Sound No No 3/8″ 1/2″ 1″ 1 1/2″ Max. Size—Repaired 1/8″ 1/2″ 3/4″ 1″

Avg. 1 per 8 sq ft 1 per 8 sq ft 1 per 6 sq ft 1 per 2 sq ft Number—Repaired

Mineral Streaks No Slight, Few to 12″ Yes Yes Yes Blending Bark Pockets No No Few to 1/8″ × 1′ Few to 1/4″ × 2′ Yes 1/4″ × 2′ Worm Tracks No No Slight Few Yes Yes Vine Marks Slight Slight Yes Yes Yes Yes Cross Bars Slight Slight Yes Yes Yes Yes

For other characteristics including color and matching, manufacturing characteristics, and other special characteristics, and other species, see: ANSI/HPVA HP-1 American National Standard for Hardwood and Decorative Plywood© www.hpva.org Hardwood Plywood and Veneer Association Figure 16-15. Face grades are species dependent. More and larger characteristics are allowed progressively with the alphabetical grade designation. This table shows specific information on natural characteristics from the ANSI/HPVA HP-1 standard for Red and White Oak.

The following orders are examples that would be 16.2.3 Prefinished Plywood understood by any plywood dealer. • 5 pcs. 3/4″ × 48″ × 96″, lumber core, plain sliced Paneling walnut, slip matched, A-1, Ext. Prefinished plywood panels are used primar- • 3 pcs. 1/4″ × 48″ × 96″, 3 ply, half-round sliced ily as wall covering and are offered in a variety of red oak, B-2—Sound red oak back, Int. styles, colors, and textures. See Figure 16-17. Both hardwood and softwood veneers are used.

/ 246 Section 3 Materials

Natural Characteristics (Except as limited below, Natural characteristics are not restricted) Grade 1 Back 2 Back 3 Back 4 Back Description Sapwood Yes Yes Yes Yes Discoloration and Stain Yes Yes Yes Yes Mineral Streaks Yes Yes Yes Yes Sound Tight Burls Yes Yes Yes Yes Sound Tight Knots Max. diameter 3/8″ Max. diameter 3/4″ Max. diameter 11/2″ Yes Maximum Number of Tight 16 S216 Unlimited to 1/2″ Unlimited Knots No more than 16 from 1/2″ to 11/2″ Knotholes No 1/2″ Repaired 1″ 4″ Maximum Combined Number All repaired Unlimited to 3/8″ Unlimited of Knotholes and Repaired Unlimited to 3/8″ No more than 10 None* Knots No more than 8 from 3/8″ to 1″ from 3/8″ to 1/2″ Wormholes Filled** Filled** 1″ 4″ Splits or Open Joints Yes, 3/8″ × 1/4″ 1″ to 1/4 LOP, Yes, Six 1/8″ × 12″ Six 3/16″ × 12″ Length of Panel 1/2″ to 1/2 LOP, repaired repaired (LOP) 1/4″ to Full LOP Doze and Decay Areas of doze and decay provided Firm areas of doze Firm areas of doze Firm areas of doze serviceability of panel is not impaired Rough Cut/Ruptured Grain Two 8″ diameter 5 % of panel Yes Yes areas Bark Pockets 1/8″ wide repaired 1/4″ wide repaired Yes Yes Laps No Repaired Yes Yes *repairepdin knots and pin knots allowed **unfillewdormholes shall be a maximum of 1/6″ in diameter For other back grade requirements, see section 3.4 BACK GRADES in ANSI/HPVA HP-1 American National Standard for Hardwood and Decorative Plywood© www.hpva.org Hardwood Plywood and Veneer Association Figure 16-16. Back grades are designated by number and are more generic than face grades, though some species have specific grading rules. Grades 1 and 2 require sound surfaces, with all openings repaired except small vertical wormholes.

Prefinished panels range from 5/32″ (4 mm) to 16.2.4 Simulated Wood Grain 3/4″ (19mm) thick. Thin panels are usually applied over gypsum board covered walls. Thicker panels are Finish Paneling sturdy enough to be attached directly to wall studs. Face veneers are either rotary cut or plain sliced. Simulated wood grain finish panels are plas- Commonly used species are pine, fir, oak, birch, and tic laminates over either plywood or wood fiber walnut. The face veneers are finished with a topcoat substrate. Examples include hardboard, MDF, and to protect against moisture and wear. particleboard. The appearance is much the same as Prefinished plywood panels are sometimes tex- prefinished plywood panels. See Figure 16-18. The tured, with grooves running the length of the panel. panel is coated with acrylic finish for moisture pro- The panel looks like multiple boards of varying widths. tection and wear resistance.

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Patrick A. Molzahn Figure 16-18. Simulated wood grain paneling is designed to look like real wood.

Engineered board products are manufactured rj lerich/Shutterstock.com by various methods. For medium- and high-density Figure 16-17. Prefinished paneling is used for wall fiberboard, wood fibers are mixed with resin. They decoration. are then bonded by either radio frequency (RF) adhesion or heat. Low-density fiberboard and particleboard are manufactured using heat and pressure. The wood fiber substrate used on some simu- The fiber and resin mixture and amount of pressure lated finish panels can be damaged by moisture and determine the strength of the board. heat. Do not install them in hot or moist areas. 16.3.1 Fiberboard 16.2.5 Prehung Wallpaper Fiberboard is a very dense, strong, and dura- Paneling ble material that is commonly used for case goods, Figure 16-19. Fiberboard is manufactured from Prehung wallpaper paneling combines the refined wood fibers separated by either steam or ease of panel installation with the design appeal chemicals. The fibers are randomly arranged into of patterned wallpaper. The paper is laminated a continuous mat that is cut into sheets called onto a plywood or a wood fiber substrate. Grooves wetlaps. The sheets are cured under pressure by add texture to the appearance of the panel. Like heat or radio frequency (RF) bonding. RF bonding other panels, finish may be applied to the surface works like a microwave oven. The panel is cooked for protection. from the inside out. This provides uniform density throughout its thickness. The amount of pres- 16.3 Engineered Wood sure determines panel density. Cured sheets are trimmed to dimension and packaged for shipping. Products Fiberboard is classified into three densities. Each has specific applications in the furniture industry. Engineered wood products are designed and manufactured to meet specific purposes. They may be installed for strength, appearance, or cost criteria High-Density Fiberboard (Hardboard) not available in other natural wood products. Many High-density fiberboard (HDF), commonly engineered wood products have applications in the called hardboard, is an extremely rugged material. furniture industry for strong and durable panels. Advantages over less dense panels include increased

/ 248 Section 3 Materials durability, strength, and resistance to abrasion. It is • Striated. Closely spaced grooves are applied for widely installed for drawer bottoms, cabinet backs, texture. and paneling. • Embossed. Textured patterns, such as basket The strength of hardboard permits thin pan- weave, are pressed into the board. els—1/8″, 3/16″, and 1/4″ (3 mm, 5 mm, and 6 mm)— • Grooved. V or channel grooves are cut into the to be used in places normally requiring thicker pan- board for appearance purposes. els. Panel measurements are typically 4′ wide by 8′, 10′, 12′, or 16′ long. Panels can be surfaced on one • Laminated. Used as the wood fiber substrate (S1S)or two sides (S2S).The unsurfaced side of S1S for simulated wood grain appearance panels. has a screen-like texture. Medium-Density Fiberboard Types of Hardboard Medium-density fiberboard (MDF) is manufac- Hardboard is classified into three types. These tured in much the same way as hardboard, but in types are standard, tempered, and service. greater thickness. Materials used for the construc- • Standard hardboard. The strongest of the tion of MDF are small particles of hardwoods, soft- three. It has good finishing qualities. woods, or a combination of both. Some manufac- • Tempered hardboard. Standard hardboard with turers now use recycled paper. MDF is also formed a chemical treatment applied to the surface to with less pressure. The added thickness, lack of increase strength, stiffness, and moisture resis- grain pattern, and smooth texture of MDF make it tance. This treatment makes it darker in color. ideal for replacing solid lumber. Surface stability • Service hardboard. Weaker and lighter than and resistance to cracking due to the elimination of standard hardboard, it is used in lightweight joints are added advantages. It is often used as a base applications. In addition to normal 4′ × 8′ size, material for stained, painted, printed, or laminated service hardboard is often available in smaller applications. MDF is commonly used for furniture sizes. tops, drawer fronts, mouldings, cabinet construction, shelving, and various millwork. Specialty Panels The random orientation of fibers in MDF means Hardboard can also be purchased as specialty it is equally strong in all directions. There are no panels. These include perforated, striated, embossed, issues associated with grain orientation as with solid grooved, and laminated. lumber and plywood. The lack of fiber direction also • Perforated. Round, evenly spaced holes are improves other factors. Warp is virtually eliminated. drilled or punched. See Figure 16-20. Sawing or machining MDF produces fairly smooth Perforated hardboard is often called pegboard. edges. Careful surface preparation is still required, Metal hangers (pegs) can fit into the holes to however, for high-grade products. hold tools and utensils. It then serves as a wall covering and storage panel.

Sever180/Shutterstock.com Panel Processing, Inc. Figure 16-19. Clamps being used to glue fiberboard Figure 16-20. Perforated hardboards are available with workpiece. multiple overlays or as standard hardboard.

/ Chapter 16 Manufactured Panel Products 249

MDF is available in thicknesses ranging from 3/8″ 97″ to 121″ (2464 mm to 3073 mm), in increments of 24″ (10 mm) to 1 3/4″ (44 mm). Standard sizes are either (610mm). Some manufacturers provide the industry 49″ (1245mm) or 61″ (1549mm) wide, with lengths with panels as large as 5′ × 24′ (1245mm × 7341 mm). 97″ to 193″ (2464 mm to 4902 mm), in 24″ (610 mm) Besides these large sheets, shelving and countertop increments. Some manufacturers provide industry- panels are available in 13″ (330 mm), 17″ (432 mm), requested panels with nominal sizes as large as 25″ (635 mm), and 31″ (787 mm) widths. Indus- 5′ × 24′ (1245 mm × 7341 mm). MDF is manufactured trial particleboard is available in 1/8″ (3 mm), 1/4″ approximately one inch larger than the nominal size (6 mm), 1/2″ (13 mm), 5/8″ (16 mm), 3/4″ (19 mm), to allow for trimming to finished dimensions. For 1″ (25 mm), 1 1/8″ (29 mm), 1 1/4″ (32 mm), and example a 4′ wide panel measures 49″. 1 1/2″ (38 mm) thicknesses. Industrial particleboard is manufactured 1″ Low-Density Fiberboard (25 mm) larger than the nominal dimension to allow Low-density fiberboard (LDF) is a lightweight for trimming to finished dimensions. Beware of panel commonly found in the upholstery industry. using particleboard for long-span shelving. It has It provides more bulk than strength. It is approxi- a tendency to sag, especially in locations with high mately half the weight of MDF. Panel sizes are typi- heat or humidity. cally 1″ × 49″ × 97″ (25 mm × 1245 mm × 2464 mm). 16.3.3 Mende Particleboard 16.3.2 Industrial Particleboard Mende particleboard is a low cost alternative Industrial particleboard is composed of either to fiberboard. It is less dense than hardboard. It is small wood flakes and chips, or fibers. These are manufactured in 5/32″ (4 mm) to 1/4″ (6 mm) thick bonded together with resins or adhesives. See sheets. These are suitable for use as drawer bottoms, Figure 16-21. Three layers of wood chips are used. cabinet backs, picture frame backs, and as substrate The two surface layers have smaller chips for a for simulated wood grain paneling. Refer again to smoother texture and increased impact resistance. Figure 16-21. It is available in 97″ (2464 mm) sheets High-quality manufacturing ensures dimensional that are 49″ (1245 mm) or 61″ (1549 mm) wide. stability and machinable edges. Because of its smooth surface, industrial par- 16.4 Working with Panel ticleboard is often used as substrate material for laminations. Cabinets, furniture parts, countertops, Products tabletops, and drawer fronts are commonly made of particleboard. It is not as dense as hardboard or Panel products are used in place of solid wood MDF. However, it adequately resists denting, crack- for many applications. They provide superior perfor- ing, and chipping. It is also less expensive. mance qualities in many situations. However, when Industrial particleboard is fabricated in dimen- working with panel products, special considerations sions suited to cabinetmaking. Standard panels are are required. 49″ (1245mm) or 61″ (1549mm) wide, in lengths from 16.4.1 Storing Panel Products Panels should be stored flat, never upright. Lean- ing the panel against a wall causes it to warp. The edges might also be damaged. Industrial Panels are subject to moisture just like solid wood. particleboard A conditioned environment will reduce dimensional changes of the panel that could cause warping.

Mende 16.4.2 Sawing particleboard Panels with veneer cores may be sawn using either a handsaw or a power saw. When using a stationary Georgia-Pacific Corp. table saw or handsaw, make sure the good face of the Figure 16-21. Particleboard is common in cabinets and panel is facing up. The bottom will tend to chip. This furniture. It is often covered with a plastic laminate. will prevent splintering of the face veneer. If you are

/ 250 Section 3 Materials using a portable circular saw, this rule is reversed— plywood, waferboard, oriented strand board, or par- place the good face down. This is because splitting ticleboard is minimal. Higher density fiberboards occurs as the teeth exit the panel. Good quality, sharp have only slightly better edge strength. saw blades with proper tooth design will greatly The face of a panel has good to excellent screw- reduce chipping. holding strength, but also depends on the type of panel. For example, Mende particleboard is limited in screw-holding power. It should only be used 16.4.3 Planing when strong joints are not needed. Reinforcement Rarely do panel products need to be planed. with solid lumber may be required. Faces are manufactured to be smooth, with a uni- The nail or screw you use should be proportional form thickness. If panels are sawn properly, the in size to the panel. As a rule of thumb, the length of edges should be straight. If you have to straighten the fastener should be at least three times as long as the edges, use a panel saw, straightedge with a router, the thickness of the panel. For example, when attach- or a jointer equipped with carbide knives. Watch ing 3/4″ plywood onto a frame, use a 2 1/4″ fastener. for and remove any staples in the edges. Staples To reduce splitting, predrill the hole. For a nail, are placed in the edges of panels at several stages use a bit slightly smaller than the nail’s diameter. between the factory and the shop to attach inventory For screws, more than one hole size may be needed. papers, routing tags, and delivery slips. Refer to Chapter 20. Nails and screws should be countersunk into the face material. A plug, button, or wood putty may be 16.4.4 Machining put over the fastener to hide it. When using wood Hardboard, medium-density fiberboard, and putty, apply it slightly higher than the panel sur- particleboard are often machined for use as counter- face. The putty will shrink slightly as it dries. Sand it top or moulding. These materials are shaped in the flush with the panel when it is dry. same way as solid wood. Since there is no grain in these panels, they will machine very smoothly and will not splinter. 16.4.7 Applying Edge Treatments When shaping an edge that will be exposed, The edges of panel products are usually covered remember to leave room for edge treatment. Wood- to hide the core composition. There are a variety veneer tape and most plastic laminates are 1/32″ to of edging materials that can be used. You can use 1/8″ (0.8 mm to 3 mm) thick. Plastic and solid wood wood, metal, and plastic. The form of the edging and edges are also applied that are up to 3 mm or more the method of bonding will differ. Common applica- in thickness. tions are shown in Figure 16-22.

16.4.5 Sanding Most unfinished panel products are relatively smooth before they reach you. However, they are not ready for finishing. Depending on the applica- Metal Edge Self–Edge tion, you may want to sand the panels before assem- bly. If you machine an edge, this will also require sanding. The same methods of sanding are used on both solid wood and panel products. However, use caution when sanding plywood or other veneer face All Wood Edge Front Wood Edge panels the veneer is very thin. Removing too much wood will expose the core.

16.4.6 Using Screws or Nails Edge Banding Plastic or Metal “T” Insert Edge The nail or screw holding ability of a panel Goodheart-Willcox Publisher is related to its density. Panels that are light and Figure 16-22. Plastic, wood, or metal edging is applied weak will not hold fasteners as well as heavier and to the edges of panel products. It hides the composition stronger panels. The weakest part of a panel is its of the panel. Do not use metal edging of this type where edge. The ability for screws to hold in the edges of food is prepared.

/ Chapter 16 Manufactured Panel Products 251 Summary Test Your Knowledge • Manufactured panel products are commonly Answer the following questionsusing the information used for case goods and furniture. These man- provided in this chapter. ufactured panels are stronger than solid lumber 1. Which of the following statements regarding and offer increased stability. structural wood panels is true? • The three types of manufactured panel prod- A. They are selected when stability and ucts are structural wood panels, appearance strength are required. panels, and engineered board products. B. They are used for roof, wall, and floor sheathing. • Most structural wood panels are used in build- C. There are a variety of ways to manufacture ing construction. These are performance-rated the panels. panels. D. All of the above. • Other structural wood panels are used in cabi- 2. Explain the manufacture of plywood. netmaking or in assembling case goods. 3. What are face veneers? • Structural wood panels include plywood, com- 4. True or False?Structural plywood is considered posite panels, structural particleboard, and ori- an appearance product. ented strand board. 5. _____ plywood has a solid wood center and • Most interior woodwork is made with appear- thin veneer faces. ance panels. 6. The edges on _____ have poor screw-holding • Hardwood plywood is commonly used for cab- capabilities. inetry and furniture. It has the appearance, 7. List the information found on a plywood grad- strength, and durability of solid lumber, yet is ing stamp. much less expensive. 8. _____ refers to the number of face veneer • Other appearance panels, such as prefinished defects and the methods by which they are plywood, simulated wood grain, and prehung patched. wallpaper paneling, make good wall covering A. Group number material. B. Veneer grade • Engineered board products are fabricated for C. Core grade special purposes. D. None of the above. • Hardboard and Mende particleboard are used 9. Name four commonly used adhesives used to as drawer bottoms, cabinet backs, and other bond the layers of plywood. applications requiring thin panels. 10. Waferboard and oriented strand board are bonded by _____ adhesive. • Medium-density fiberboard is often used as a A. melamine substitute for solid wood mouldings, drawer B. phenolic resin fronts, and various millwork. C. resorcinol • Industrial grade particleboard is used for coun- D. urea formaldehyde tertops and tabletops. Its smooth surface allows 11. _____ structural wood panels are designed to high-quality laminates to be applied. span specified distances. 12. List four materials used for hardwood plywood cores. 13. Grades for hardwood plywood are based on the quality of the two _____. 14. _____ grades are assigned to panels that do not meet the grading criteria. A. Premium A-1 B. Special C. Premium A-2 D. Shop

/ 252 Section 3 Materials 15. Plastic laminates over either plywood or wood Suggested Activities fiber substrate are known as _____. A. simulated wood grain finish panels 1. Obtain at least three different panel types such B. prefinished plywood paneling as plywood, particleboard, MDF, or OSB. Cut C. prehung wallpaper paneling each panel into a 12″ square. Carefully weigh D. engineered wood products each sample, and calculate the weight of each 16. Name a common use for fiberboard. panel per cubic foot (ft3). Note that you will need to take into account the thickness of each 17. List three advantages of hardboard over less panel when determining the number of panels dense panels. per cubic foot. Ask your instructor to review 18. Name applications for the following manufac- your answers. tured products. 2. Describe the physical appearance of the panels A. MDF you used in the previous exercise. Which do B. low-density fiberboard you prefer and why? Share your observations C. industrial particleboard with your class. D. Mende particleboard 3. Obtain 12″ × 42″ pieces of three different panel products, and one solid board, all of equal thickness. Place a brick or narrow board at each end of the sample. Ask a classmate to stand in the middle of the span and measure the deflection of the material. Repeat for each sample. Which material had the most deflection? Which had the least? Share your observations with your class.