MDF is one of the junk "woods" of the lumber industry, literally it's the left over stuff ground up and bound together with chemicals in sheets to make it usable. It's heavy, it sags, it falls apart when wet, can't hold a nail or screw and generally is a pile of junk. So why is it used so much? Well it's CHEAP and easy to put a veneer on it and call it "wood" and in todays throw away society this is all that matters to some. MDF is used in a lot of cheap furniture, toys, flooring, plywood (which I have a hard time calling it plywood) and other products. Seriously... look at any piece of furniture made with MDF with a veneer and it will be chipped, sagging and falling apart after a couple of years.
What is it?
Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood and/or softwood left overs (unusable parts) into wood fibres and combining it with wax and a resin binder forming it into panels by applying high temperature and pressure.
Advantages
- Consistent size.
- Shapes easily (when cutting small details they can chip out easily).
- Stable dimensions (less expansion and contraction than natural wood) in non humid environments.
- Cheap cost.
- No grain which makes it easy to veneer so it will not telegraph the grain through the veneer.
Drawbacks
- A lot Heavier than plywood and most other real wood.
- MDF will swell and fall apart when saturated with water unless using waterproof type.
- Will warp or expand in humid environments if not sealed.
- May release formaldehyde, which is a known human carcinogen and will cause allergy, eye and lung irritation when cutting and sanding.
- Dulls blades more quickly than many woods: Use of tungsten carbide-edged cutting tools is almost mandatory, as high-speed steel dulls too quickly.
- Doesn't hold screws or nails very well.
- Sags under it's own weight let alone anything you put on it.
Types
- Low Grade: This is usually the only type found at big box stores, this is the least dense, most fragile worst type of product you could ever use for anything. You want cheap this is the one, just don't bother with making anything useful that lasts more then a couple years at most out of it.
- Premium Grade: There is a premium version that is usually available at a lumber yard not your big box store. It features more uniform density throughout the thickness of the panel. This version is more Stable and shapes/cuts better.
- Moisture Resistant: Moisture resistant MDF does exist and can sometimes be hard to find depending on the area. It's far more resistant to moisture due to the binding agents used.
- Fire Retardent: As the name applies it's binder includes fire retardant properties or mixed in with the wood fibers is a fire retardent fiber.