Composite materials have become widely used for the cores of all types of kitchen cabinets. To understand the differences between composite materials, you need to know the differences between hardwood and softwood. Hardwood comes from deciduous trees (whose leaves fall off once a year), whereas softwood comes from evergreens.
Plywood is made of thin sheets of wood veneer that are laminated in alternating directions. It’s strong and doesn’t pose the warping or shrinking potential of solid wood. Both hardwood plywood and softwood plywood come in a variety of grades. A hardwood plywood panel for a cabinet should have one face graded A and the other graded 2 or better. Softwood plywood has a different system of ratings. It’s rated according to its face veneer (the outermost plies) and should be rated B or better. Used as a core material for kitchen cabinets, softwood plywood can be covered with a plastic laminate or wood-veneer face.
When you look at cabinetry, you can’t assume that a hardwood veneer is necessarily covering a hardwood core, so if you have doubts, ask your designer, dealer, or remodeler to clarify the matter for you.
Hardwood plywood will generally be a higher quality core, although a Medium Density Overlay (MDO) softwood plywood, covered on one or both faces with a thin resin-fiber overlay, is suitable if you intend to paint the cabinets.
There are different grades of hardwood, softwood veneers and composites. Two common varieties of composite materials are used as kitchen cabinet cores.
- Medium-density fiberboard (MDF) is made of very fine wood fibers that are glued and compressed under great pressure. It has a very smooth surface and has greater screw-holding power than particleboard, the other composite material. It is less expensive than plywood, but more expensive than particleboard.
- Particleboard is a combination of wood chips, shavings, fibers, and adhesives. It differs from medium-density fiberboard in appearance, since its larger wood chips are in the core, and smaller, finer chips are on the surface. It’s heavier than plywood, but not as strong.
If a plastic laminate is going to be applied to the core material, the material shouldn’t be of lesser quality than industrial-grade particleboard. Low-grade particleboard won't be able to support the weight of the laminate, and screws and staples won't hold over the long term, resulting in loose cabinets or doors.
One distinct disadvantage of choosing kitchen cabinets constructed with pressed woods like particleboard, hardwood plywood, or medium-density fiberboard is the emission of a gas, formaldehyde, from the adhesives used in their construction. Of all the pressed woods, medium-density fiberboard emits the greatest amount of formaldehyde gas.
According to the U.S. Environmental Protection agency, formaldehyde gas can cause respiratory and other physical ailments in some people exposed to elevated levels of it (above 0.1 parts per million). Although the EPA estimates that most older homes have significantly less concentration of concentrated gases in their kitchen cabinets.
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