Q: For a variety of reasons, we are considering using MDF for some of our products with a veneer overlay. My question is "What is MDF and what should we be aware of?"

A: Medium density fiberboard is a fiber product. That is, the wood is defiberized, making the wood into individual fibers or clumps of several fibers. The fibers are then glued back together using heat and pressure. Wax is oftentimes added to the fibers before gluing. By controlling what goes into the product and the pressures and temperatures used, MDF will have a fairly wide range of properties. In other words, not all MDF is the same.

MDF began being used in large quantities in the 1980s. Two relatives of this product are low density fiberboard (without adhesive and without much pressure) which is used for ceiling tiles, and high density fiberboard, which uses high heat and high pressure without adhesive (which is known to many as Masonite).

Here are a few items to consider about MDF:

It may be less expensive than solid wood; may be easier to work with; is consistent in size and properties from piece to piece; expands and shrinks a little in all directions with humidity changes (compared to wood that moves much more, primarily across the grain); and is very smooth. On the other hand, MDF is heavier (more dense); is not usually used with transparent finishes as there is no grain; may have wax that interferes with gluing unless sanded before gluing; is especially sensitive to liquid water; and the adhesive may dull knives more rapidly than solid wood. In the past, there was also concern about the formaldehyde in the adhesive, but different adhesives are being used to eliminate this problem. Another major concern with MDF is fastening with nails and screws, especially on the edges; special fasteners should be used to obtain the needed strength. As a shelf, MDF is not as strong and stiff as solid wood. Overall, there will be a learning curve, but it should not be hard to learn what you require. Remember, there are many people who are satisfied using MDF instead of solid wood.

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