A decade after emergency trailers meant to shelter Hurricane Katrina victims instead caused burning eyes, sore throats and other more serious ailments, the Environmental Protection Agency is on the verge of regulating the culprit: formaldehyde, a chemical that can be found in commonplace things like clothes and furniture (Lipton & Abrams, 2015, para. 1).
Plywood, commonly found in building construction sites, is a composite panel made of thin slices of wood bonded by glue (Hoadley, 2000, p. 229). The Canadian government declared formaldehyde a toxic material (Government of Canada, 2014, p. 236) and pointed that the glue used in plywood as a source of formaldehyde (Health Canada, 2012, para. 4). With those health risk warnings, some may wonder why the government does not completely ban plywood production. In pursuit of understanding formaldehyde danger, I found the other side of plywood. Plywood is not just a cheap and harmful substitute of solid wood; it is strong, stable, and sustainable.
First, plywood is used for construction and furniture-making not only because of its low price, but because of its strength. Compared to solid wood, which is strong in vertical direction but weak in horizontal direction, plywood is strong both in longitudinal and latitudinal directions due to its cross layering structure. Even more, in certain cases, “pound for pound, plywood is stronger than steel” (Umstattd et al., 2016, p. 234). Thanks to the equalized strength, plywood can be made lighter in weight than solid wood with the same strength. The weight of the plywood panel can be reduced even more by smart design of core structure. By using a honeycomb structure, which is a hexagonal shape found in honey bee nests, one company is producing a light weight panel that does not increase the weight at the same rate as the thickness is increased (Panolite, n.d., para. 1). Builders and cabinetmakers prefer plywood because it is strong in strength, and it is light in weight as well.
The second reason why plywood is used for construction and cabinet making is its dimensional stability. Wood does not stand still like steel or plastic. Actually, wood expands and contracts according to relative humidity of the environment. Generally speaking, wood changes its size 8% in width and 4% in thickness with moisture change (Hoadley, 2000, p. 118). This is why a wooden door or a window is tight in the summer but loose in the winter. It is an even bigger problem in large wood panels for the walls of the house. If the wall is 10 feet wide, dimensional change could be up to 9.6 inches. It is quite challenging to cope with. Plywood is a solution for this dimensional instability. Douglas-fir plywood has only 0.5% of size change in width with environmental moisture. Compared to 7.8% in solid wood form, the size change of douglas-fir plywood is 1/15 of solid wood’s swing (p. 236).
Another problem of solid wood caused by environmental moisture change is the warpage. Due to the unbalanced shrinkage rate between width and thickness, wide boards made of solid wood tend to warp. To solve this distortion problem, it is common to break down to several smaller width boards and to glue them together with alternating growth ring direction (Umstattd et al., 2016, p.584). Plywood, however, is free from warpage due to its constructional nature. Cross layering of slices of wood neutralize the difference of directional shrinkage rate and make plywood plat even in a wide board form. For example, standard plywood is produced as the 4-ft. by 8-ft. sheet in one piece that is hard to get in natural solid board form (Hoadley, 2000, p. 229). Plywood makes woodworkers free from expansion and warpage problems of wood.
The third reason why plywood is superior to solid wood is that it is sustainable. As Umstattd et al. (2000) states, “a tree can cover 30 to 50 times more surface area when used to produce veneer than when producing solid lumber” (p.257). Veneer is the face material in plywood, so plywood, providing the same quality of surface, can cover far more area than solid wood, which reduces the demand of forest resources for good quality wood. Another advantage of plywood is thorough utilization of the tree. The usable portion of the tree for cabinet making is actually not so large. In the process of sawmilling, only the major stem of a tree is cut to lumber; other parts of a tree, including small branches, are not used, and a substantial amount of wood is turned to saw dust. In addition to that, the usable area of lumber for furniture making is only 65% in No. 1 Common grade that is the commonly used grade for the average woodworker (Hoadley, 2000, p. 222). Instead of dumping or burning the materials thrown out by the process, those waste materials can be used for the core of plywood; this also reduces the number of trees that need to be cut down.
Even though those merits of plywood are prominent, no one would gladly use plywood for their home as a form of furniture, floor, and wall if it produces harmful gas: formaldehyde. In order to meet customer requests and government guidelines on the formaldehyde level, the industry has been developing new glue technology. One plywood company recently developed a new glue that does not produce formaldehyde gas into the air (Colombia Forest Product, n.d., para. 2). The newly developed glue is a natural substance-based one that is not related to formaldehyde. Industry association is not an exception; the Canadian Plywood Association devised a certification program that guarantees nearly undetectable level of formaldehyde emission for their exterior grade plywood (Canadian Plywood Association, 2011, para. 8). Formaldehyde detection testing and bond specification are part of the program, so customers can easily check whether it is certified or not by finding the program’s logo.
In conclusion, plywood is a useful form of wood because it is strong, stable, and sustainable. The way that plywood is made makes it stronger than solid wood. The nature of plywood structure also resolves its shrinkage problem induced by moisture change and makes it dimensionally stable. Even more, the thin slice of wood used in plywood, which covers far larger surface than solid wood, and re-utilization of wood waste for plywood core contributes to forest conservation. With all merits of plywood and the advancement of non-toxic glue technology, there is no reason to refrain from using plywood.
Canadian Plywood Association (2011). Formaldehyde Emissions [Technical Note TN02-2011]. Retrieved November 22, 2015, from http://www.canply.org/pdf/main/tech_notes/tn02-2011.pdf
Columbia Forest Product (n.d.). PureBond Hardwood Plywood. Retrieved November 22, 2015, from http://www.columbiaforestproducts.com/product/purebond-classic-core
Government of Canada (2014). The Canadian Environmental Protection Act, 1999. Retrieved November 29, 2015, from http://www.ec.gc.ca/lcpe-cepa/26A03BFA-C67E-4322-AFCA-2C40015E741C/lcpe-cepa_201310125_loi-bill.pdf
Health Canada (2012). Formaldehyde. Retrieved November 22, 2015, from http://www.hc-sc.gc.ca/ewh-semt/air/in/poll/construction/formaldehyde-eng.php
Hoadley, R. B. (2000). Understanding Wood: a craftsman’s guide to wood technology. Newtown, United States: The Taunton Press.
Lipton, E., & Abrams, R. (2015, May 3). The Uphill Battle to Better Regulate Formaldehyde. The New York Times. Retrieved November 24, 2015, from http://www.nytimes.com/2015/05/04/business/energy-environment/the-uphill-battle-to-better-regulate-formaldehyde.html
Panolite (n.d.). Panolite Specifications, Retrieved November 29, 2015, from http://www.panolite.com/media/upload/PANOLITE_SPECIFICATIONS_18-9-2012_IIDEX.pdf
Umstattd, W. D., Davis, C. W., & Molzahn, P. A. (2016). Modern Cabinetmaking (5th ed.). Tinley Park, United States: The Goodheart-Willcox Company.