What Is Block Board?
Block boards are not recent invention. In fact the Egyptians had conceived and built furniture with block boards in their pyramids dated back thousands of years ago.
Block board (also known as lumber core) is a man-made board similar to plywood but the center layer or core is made from strips of softwood.The strips are put edge to edge and sandwiched between veneers of softwood, hardwood, particleboard or MDF (medium-density fiberboard), pasted under high pressure and heat with glue.
In terms of construction, there are three main types of block board , i.e. 3-ply, 5-ply and 7-ply.
A 3-ply block board consists of a core sandwiched between two layers of veneers whereas a 5-ply and 7-ply block boards are made of a core and covered with 2 layers and six layers of veneers on each side respectively.
The first one is normally used for hidden application. The second is preferred to build furniture that requires decorative quality. The last is utilized more in manufacturing doors and construction.
The picture below shows an example of block boards.
An exploited view of a 5-layer blockboard is illustrated below.
The following pictures show some good examples of what block boards can be utilized for so far as furniture are concerned.
Depending on the market, the most common sizes are: 2070x5200mm (German), 1850x3660mm (Italian), and 1220x2440mm (Chinese). Thickness varies from 13mm to 60mm.
Manufacturers can fabricate a variety of applied finishes for block board such as plastic laminate surfaces, wood veneers and melamine papers.
Classification Of Blockboards
Basically block boards can be classified based on: (1) types of wood used i.e. softwood and hardwood, and (2) composition and quality, i.e. grades.
(1) Classification Based On Core:
The cores, which consist of softwood strips placed adjacent to each other lengthwise, are sandwiched with one or more hardwood veneers.
The cores and veneers are both made of hardwood. Not only are they heavier, they are more expensive in general.
(2) Classification Based On Grade:
Moisture-Resistant (MR) grade block boards are used to fabricate furniture and doors.
Comparing to MR grade block boards, Boiling-Water-Resistant grade ones provide superior quality for exterior applications.
Advantages Of Block Boards
Besides being a poor conductor of sound, heat and electricity, block boards are light, stable, easy to cut, reclaim and to preserve in sea water than most competitive materials. In addition, these boards are cheaper, lighter, stronger and more resistant to warpage as compare to raw wooden planks. Owing to their light weight, block boards extend furniture and door life span as they exert less stress onto hinges.
Basically there are 6 steps in fabricating block boards:
1. Mixing glue using a glue mixer with water and powder resin proportionally.
2. Spreading the glue on core and veneer by using a glue spreader.
3. Setting different layers of core and vaneers on wooden batten frame and followed by compressing under high pressure and temperature with a hydraulic press.
4, Drying the boards.
5. Using a saw cutting machine to perform side cutting.
6. Finally, top layer finishing is done by a sanding machine.
As this article is meant for the general public, I have skipped the technical aspects such as mechanical/physical properties, specifications and quality standards.