Physical characteristics are those that remain unchanged despite changes in the size, form, and chemical makeup of wood.
The physical properties of wood are discussed as under:
Color of wood
From a functional or decorative standpoint, the color of the wood is crucial. Multiple extractives found in the heartwood cell wall give wood its distinctive color. The following factors could alter the color of the wood:
- With time, many kinds of wood turn darker.
- Due to the effects of sunlight, some wood is changing color.
- During kiln seasoning, moist heat is applied, changing the color of the wood from lighter to darker.
- By using various chemicals on wood, the color also changes. For instance, liming lightens the color.
Luster
The quality of wood elements and their contents that tend to reflect light can be described as their luster. Color is significant from a decorative perspective and for identifying wood.
The following elements impact wood’s luster:
- observer’s inclination
- The descending light plane
- the capacity of the cell wall to reflect light.
Odor and Taste
Many types of wood have a distinctive odor, which works best in dry conditions. However, with time, it progressively vanishes. Spicy aroma of sandalwood, deodar, teak, juniper, etc.
The odor and taste of wood are closely connected and most likely derived from the same components.
Density of Wood
The definition of density is “mass per unit volume.”
Weight/mass is often divided by volume to produce density. Defined as: Density = weight / volume
While balance determines weight; length, breadth, and height can be multiplied to determine volume.
The ideal standard size for the wood piece is 5–6 cm by 2 cm by 2 cm.
Density is calculated by:
- Making use of a volume meter
- Using weight, balance, and a beaker.
Hardness
Hardness is described as “the resistance provided by the wood to indentation (to form a dent)”
An electronic gadget known as a Janka, which is made of hard steel, is used to test the resistance. The size of the standardized wood sample is 10 x 2 x 2 cm
Two methods are typically used to determine hardness:
- Janka Method (for determining the composition of wood)
- Brinell Method of Matters
Wood moisture relation
Sound moisture in the cell wall during seasoning has a detrimental effect that results in degeneration, distortion, and degradation (seasoning defects.)
The mechanism is known as case hardening.
When considering moisture contents, we can divide the wood into four categories:
- Oven Dry
- Kiln Dry
- Air Dry
- Greenwood has a moisture content of 25-50%
- Thermal and electrical conductivity
The conductivity of a wood sample refers to its capacity to transfer heat.
Due to its porous nature, wood conducts heat rather slowly, which is one of the reasons why it is used to make building materials, furniture, and other things.
Compared to an iron, concrete, brick, or stone wall, a timber wall allows far less heat to pass through it.
The orientation of the fibers or grains and the density of the wood material both affect how quickly heat moves through it.
Heat/calorific value of wood
It is a process through which a given mass of wood is completely burned, producing a certain amount of heat.
Conversely, wood with a high moisture content has a lower calorific value.
Latent heat of vaporization
It is the bare minimum of heat necessary to vaporize a unit mass of water.
The majority of the heat in wood with excessive moisture contents (EMC) is used to evaporate the moisture, a phenomenon known as reducing the heat of combustion. All of our native species of plants and animals have a calorific heat value between 4500 and 5500 kcal/kg.
