In addition to solid hardwoods and softwoods, J. Gibson McIlvain Lumber proudly carries high-quality plywood. We carry both marine-grade and hardwood plywood for our customers. Why would we carry plywood, when it’s so readily available elsewhere? We carry it as both a convenience and a service to our valued customers, who know that quality is our main focus and finding high-quality plywood can be difficult.
The Truth About Plywood Layers
Some well-meaning lumber customers, in a valiant attempt to gauge quality plywood, reduce it to simply counting the number of plies. Trust us: we wish it were that easy. But it just isn’t. Sure, the number of plies does make a difference, but not quite as clearly as counting them would seem to indicate. More plies means there’s more of something else: glue. And the more glue there is, the more stability a panel will have. Reducing the natural movement of wood, more glue — and more plies — can definitely be a good thing. But it isn’t always.
The Importance of Glue
A more significant factor than how many plies and how much glue is used is the quality of glue that’s used. If more glue is used, but that glue is of inferior quality, than the overall quality of a panel will be inferior as well. Why? Glue actually accounts for approximately ⅓ of whatever you pay for when dealing with plywood. And unlike the cost of the wood itself, which fluctuates like all lumber prices, the price for glue is a constant. In order to reduce production costs and increase profits, a mill can change the quality of glue or the amount of glue used per panel. As a result, glue ends up being the element of the production process that’s manipulated most.
The Differences in Glues
When it comes to evaluating the glue used in a sheet of plywood, the issue isn’t actually as much about the chemical makeup of the glue itself as about the quality of its application. Many mills — particularly those in other countries — use extenders to increase glue coverage; since the amount of glue directly relates to the cost of manufacturing plywood, watering down the glue lowers the price point. But this inferior glue will end up costing you.
Another way that plywood manufacturers lower their overhead expenses is to use automation to reduce the thickness of glue lines. Like using extenders, automating glue application leads to using an overall lower amount of glue per panel. Another potential problem associated with automation is that plants with full automation run the risk of glue vats running completely dry during a run. Believe it or not, it’s not unheard of for a panel to delaminate, revealing that the plies have been held together with only heat and pressure, along with minute amounts of glue residue on the rollers.
Beyond the glue, there are a few other considerations to keep in mind when it comes to evaluating the quality of plywood. To learn more, take a look at Part 2.