How MDF is made

MDF is wood torn into single fibers, then blown through a pipe that widens from 40 mm to 1,500 mm.

stations: 7
things upstream: 28
raw sources: 8
steps from the ground: 8

The short version

Medium-density fiberboard is wood broken all the way down into fibers, then pressed back together. Chips are steamed soft, torn apart between grooved spinning discs, mixed with wax and resin in a fast-moving pipe, formed into a thick mat and squeezed in a hot press. The result is a smooth, grainless panel.

Chip the logs

Logs are debarked and fed to a chipper with a ring of blades. Sawmill leftovers and thinnings work too. The chips are washed and checked for defects.

Goes in
Timber
Steam the chips soft

A screw feeder packs the chips into plugs, which are heated so the natural glue holding the wood fibers together turns soft.

30 to 120 seconds
Tear them into fibers

Softened chips are fed into the center of two counter-rotating discs with grooves in their faces. Centrifugal force carries them outward, and the grooves, which get finer toward the edge, pull the chips apart into individual fibers.
Blow in wax and resin

The fibers shoot into a pipe that widens from 40 mm to 1500 mm. Wax is sprayed in first to help the board resist moisture, then a resin glue. The fibers dry on the way out and expand into a light, fluffy cloud.

Goes in
Paraffin wax Adhesive
Lay down the mat

The dry fibers are sucked into a machine that spreads them into an even mat, hundreds of millimeters thick. The mat is lightly compressed so it can move on.
Press under heat

A hot press cures the resin and squeezes the mat in stages. The two faces end up denser than the core, which gives the board its strength and a hard, smooth surface.
Cool, trim and sand

Boards cool in a rotating rack, are trimmed to size and are sanded smooth. Some are laminated afterward for extra strength.

End of the lineMDF Next it goes into sofa, treadmill, loudspeaker.

Worth repeating

A typical MDF panel is about 82 percent wood fiber, 9 percent glue, 8 percent water and 1 percent wax.
Large-scale MDF production only began in the 1980s, in both North America and Europe.
MDF has no grain, so a veneer glued to it will not show a texture telegraphing through from below.