About panel, plywood, MDF and other wood derivatives

We all like houses in bușteni or those clad with planks, furniture and solid wood flooring or beams and the support posts, also made of wood, in the attic. We think anything solid wood is both beautiful and strong. We forget, however, that there are many other derivatives of wood that, while not equalling the natural and sometimes wild beauty of wood, are more stable and resilient. I'm thinking of solid wood panels, laminated wood, paneling and plywood, but also those sometimes looked upon with reluctance, such as MDF or chipboard, but which are present in most homes (sometimes without our even knowing it). We've talked about some of them before, telling about the history of their appearance or how to finish them. This time I will briefly present all these wood blanks, trying to highlight both their pluses and minuses.

Massive panel is made of even pieces of solid wood, properly dried and cut to size, which are glued together both lengthwise and widthwise to form a panel. First, elements of the desired length are obtained by gluing several pieces of wood together toothed or straight.

Then, on one side, lengthwise, apply adhesive. The pieces of wood thus prepared are placed side by side in presses and held there until the glue hardens (cold hardening, i.e. at room temperature). Finally the panel is sanded to remove the excess hardened adhesive and then calibrated.

The advantages of such panels are better stability and much larger dimensions compared to planks cut from logs.

Disadvantages: discontinuity of the wood design, possibility of peeling, problems of non-uniformity in staining or highlighting of glue lines.

The panel is obtained from a middle, a core, made of solid wood strips, placed between 2 sheets of technical veneer (thick veneer, 3-7 mm). Usually the inner lamellas are of a lower quality wood than the upper one or lighter than it. For example, a panel can be made with a softwood core and oak faces. This way the panels will look like oak panels, but will be much lighter. Another advantage is the continuity of the design. The veneered rather than solid wood look is the main disadvantage.

Plywoodis a wood derivative consisting of an odd number of technical veneers laid perpendicular to each other. They are glued together using hot glue in special presses. It is possible to obtain 3, 5, 7 veneer sheets. Originally plywood was used more for the back of furniture or for poor quality work. Over time, because of their stability, they began to be used in production (especially thick ones with a large number of veneers glued together). Panels can also be veneered with aesthetic veneers and can be used without problems in furniture making. However, as with all blanks using gluing adhesives, care must be taken when formaldehyde emission.

Apart from this type of plywood, where the sheets are laid perpendicular, there is also plywood made of sheets laid parallel called laminated plywood.The product obtained is elastic and resistant, and is widely used to obtain support beams (glulam), but also in the seating industry. About the emergence of plywood, its evolution over time and its use in various fields (including aeronautics), find more here.

Laminated woodis a semi-finished product made from layers of solid wood. Such blanks are used for getting parchment or for double glazed window frames. Overlapping layers of wood results in increased stability. The production of laminated timber and the comparison with solid wood will be the subject of a separate article.

Wood chip boards (chipboard)are made by hot pressing wood chips mixed with adhesive resins. The most commonly used resins are ureoformaldehyde resins. During the process of obtaining the chipboard a small part of the formaldehyde in the adhesive remains free and is released over time. This is that pungent smell characteristic of new furniture. The classification of formaldehyde as a health hazard has led to the development of countless methods and products to reduce emissions, emission limits and classes have been imposed to classify PAL according to formaldehyde emission. Using the new adhesives or special products called formaldehyde scavengers, it has been possible to obtain panels with very low or even zero emissions.

Chipboard is rarely used as such. In general, they are covered with aesthetic veneer, paper (khaki), melamine, etc. They are used extensively in office and domestic furniture. We said at the beginning that we might not know we have chipboard in the house. In order to reduce production costs, veneered chipboard is often used with solid edging. A person less familiar with wood may be convinced that they have solid wood furniture in their home.

The advantage of chipboard is its low price. Disadvantages - impossibility of deep processing, formaldehyde emission (especially in cheap variants), weight.

The panels in MDF (or PAF, as it used to be called - wood chip and fibreboard) are made by hot-pressing wood fibre mixed with resins. Wood fibre is obtained by partially removing lignin from the wood. The result is a product very similar to wool. Compared to chipboard, wood fibre panels can also be used without veneer or other materials. The most popular are MDF (medium density board) and HDS (high density board). HDS is produced by the 'wet' process at high temperature and pressure. The bonding of the fibres is mainly achieved with naturally occurring resins.

MDF is obtained by the "dry" process, using low temperature and low pressure. Synthetic resins are added for gluing. MDF panels are produced with different densities or surface treatments: fire resistant, water resistant or weather resistant.

Advantages: deep machining possibilities, use as veneer or panel, stability. Disadvantages: weight, emission, price (compared to chipboard)

Aesthetic furnace,like the technical one, is obtained by unwinding or cutting the log into "slices" of wood. Unlike technical veneers, aesthetic veneers are much thinner, with a thickness of 0.5-0.8 mm. Both the quality of the wood and the machinery used are important for producing a quality veneer. Poor knife quality means veneers with defects that may not be immediately visible, but which will show up during finishing.

Depending on the cut, the design of the wood is also obtained. For example, cutting parallel to the annual rings (friz) will produce a parallel line pattern, while cutting across the rings (flader) will produce curved lines forming sequential patterns.

There is a lot to be said about each of these individual semi-finished products. Some of them have been dealt with separately, others follow. But put together they can be compared more easily, making the choice simpler.