How is hardboard made?

[sailor]

I have a basic understanding of different wood-based board products. Plywood is made of veneers glued at right angles. Particle board is made of small particles, almost like sawdust, glued together. Wafer board is made of wafers a few inches in diameter glued together. In all of these the structure is quite obvious to the naked eye but then we have hardboard which is dark brown and often used to make pegboard. It is harder than the other wood products and the structure is not obvious. I have a piece in my hands and it has a smooth and very hard side and the other side is textured and feels like cardboard. It is about 3/16" thick and I have always seen it in this type of thickness, never in the thicker dimensions common to the other wood boards. It is often used as backing for cheap furniture and for the bottom of drawers and may be painted white or other colors.

How is this hardboard made? The page I linked to does not give much information. When was it invented?

And while we are here, that site also mentions fiberboard (MDF for short) and I am not sure what this product is. Maybe it is something I am familiar with and just don’t know the name or maybe I have never seen it. Can anyone clarify what is fiberboard?

[Desmostylus]

HARDBOARD (Masonite) What is it?

MANUFACTURING PROCESSES
Fiberizing of the wood is accomplished by a variety of methods but basically they consist of steaming chips to soften them followed by grinding between abrading discs to tear the fibers apart. Green wood is about 50% water. This water plus any added in the process must be removed before hardboard manufacture is complete. The method and time of water removal is what distinguishes the various hardboard manufacturing
processes.
• WET PROCESS MANUFACTURE •
The wet process was the one first invented by Mason. In it water is added during the fiberizing process to make a pumpable slurry of wood fiber. This slurry is delivered to a screen where water is drained from the fiber leaving a soft mushy mat. More water is removed by vacuum and pressing between rolls. The wet mat, now able to support it-self, is cut to length and placed on another screen which carries it into a hot press. These hot presses usually have 20 or more “decks” or openings. They are capable of applying several thousand tons of pressure to the wet mats while heating it to a temperature of 35OºF or more.
When fully loaded the press is closed and quickly brought to high pressure, A torrent of water is squeezed out of the mat thru the carrying screens and cascades over the edge of the platens.
In a few seconds, water remaining in the mat is heated to steam. Press pressure is reduced and held for several minutes while the rest of the water is evaporated, the board is reduced to the desired thickness, and the chemical reaction to reconstitute the lignin bond is completed. The press is unloaded, the screens peeled off and we have S1S (smooth one side) hardboard, or traditional “Masonite”: smooth on the face with a screen pattern on the back. Additional operations are necessary to make it practically usable, but the process of “making hardboard” is complete at this point.

Amazing what Google and 20 seconds will do.

[sailor]

>> Amazing what Google and 20 seconds will do.

Well, yeah, if you know what you are looking for. I did not even know what the stuff was called when I started googling for pegboard and it took me close to 20 mins just to find out that the stuff was called hardboard. I then googled for “hardboard” and read dozen of pages, among them the ones I linked to in the OP, but did not find any which described the manufacturing process in detail. I hope you will find it in your heart to forgive my audacity in posting before I had searched for a full six hours and I apologize for any distress I may have caused you.

[Desmostylus]

You defined the problem very well, so no time was wasted in asking things like "do you really mean x?.

At the same time, I was genuinely surprised that that you didn’t find what you were looking for. As I said, it only took me 20 seconds.

As a bonus, here’s the manufacturing process for MDF.