From log... to solid wood!

Hello to everyone! Welcome back on CN's BLOG!
Today's post is about some technical feature: we're going to write about...SOLID WOOD.

What is solid wood? Usually this definition is used to distinguish between ordinary lumber and engineered wood. It is also known as lumber and it is made by the older part of the log, next to the center, that is called heartwood. Sapwood, instead, is used to produce veneer, as we have already seen here and here.

In order to became finished lumber, cutting a log isn't enough: there are special procedures that allow the wood to become more resistant over time and to the weathering.

After debarking, the wood can be sawn in different ways, depending on its size. This process requires a great attention, because the result should appear homogeneous and without cracks and knots. These are often visible in the core, from which the roughest material comes.
What are knots? They simply are what remains of old branches: limbs grow from the center of the log and when it grows too, new layers simply cover the start of these branches and form knots.


The sawing produces lumbers and boards, which measures are different in each country.
In Italy they are divided in different classes:
- Class A: sharp;
- Class B: round edge;
- Class C: chamfer.
Here nearby you can see the different cuts that lumbers and boards usually have.

But, before being sold, these pieces need to be treated.
We must say, indeed, that untreated wood (the log) has a 40-50% of moisture content! When wood is used as a construction material, il will absord or desorb moisture, in order to be in equilibrium with its surroundings. This equilibrium must be controlled to prevent damages: that's why wood must be dried to that equilibrium moisture. There are different ways of drying: natural (or air) or artificial. This process causes the wood to have around 20% of moisture content.
The loss of water causes the wood to become lighter and contract.

At this point, a different treatments start, to protect the wood from insects, fungi and molds. For this purpose, there are special chemical compounds or a particular way of drying, called KVH (Konstruktionvollholz), that, though a drying that reduces the moisture content to 12%, allows the wood to be ready to sell, without any other treatment.

Lumbers and boards are usually smoothed and cut at the edges, there is a selection and then they are marked and bounded.

Solid wood has some advantages:
- it is eco-friendly: it's a renewable material and for this and many other reasons is used in the green building.
- it lasts in time: it properly treated and if you take care of it, the material of first choice has a long life.
- precious: but also... expensive!
- resistant and flexible: wood is a "lining" material and can easily adapt to the surroundings.
On the other hand, you should be attentive to:
- choose very good and high quality material.
- choose a proper treatment.

A big problem of solid wood is due to its dimension: this could be solved thanks to the use of  laminated wood or using a finger joint.