Seasoning of timber: Types, advantages and disadvantages

Before wood is utilised, it is allowed to dry out under controlled conditions during a process called seasoning of timber.

In addition to enhancing the strength of wood and preventing wood rot, seasoning of timber also prevents changes in the size and shape of the wooden objects it is used to make. The primary purpose of seasoning of timber is to lower the moisture content to a level suitable for the usage of the products manufactured from it.

 

What is seasoning of timber?

Timber seasoning is a crucial construction process, ensuring wood undergoes controlled drying before use to mitigate moisture-related issues. This method targets a specific moisture content, eliminating sap to prevent decay. Seasoning enhances timber durability, reducing susceptibility to decay and playing a vital role in maintaining the quality of timber structures.

 

Seasoning of timber: Types

There are two techniques for seasoning timber, which are described here.

Natural seasoning

The process of ageing wood by exposing it to the elements of nature, such as air or water is called the natural seasoning of timber.

There are three types of natural seasoning of timber.

Air seasoning

• The earliest, most conventional, and easiest way to season wood is with air. In the process of air seasoning of timber, wood is stacked in the air, and the remaining work is left to be completed by ambient heat and natural air movement.
• It is important to have enough space between each component to allow air to flow through and around the stack. 

Water seasoning

• For the goal of seasoning of timber with water, logs are submerged in rivers with their thicker ends pointed upstream. 
• Logs are stacked in stacks and secured to a standing tree or other sturdy structure to prevent them from being swept away by the river.
• For two to four weeks, the river water washes the sap from the wood. After that, the logs are removed for additional processing to finish the seasoning of the timber. The last stage involves stacking the identical items in a dry location.

Solar seasoning

• The solar seasoning technique is a substitute for the quick operation of a kiln and the low energy need of air drying. 
• Solar seasoning of timber offers a compromise for several disadvantages of traditional seasoning processes.
• One may describe solar seasoning as a slower, more delicate version of kiln drying. Compared to air dryers, timber solar dryers dramatically lowers drying time and flaws.

Artificial seasoning

Natural seasoning produces good results, although it is time-consuming. Therefore, artificial seasoning of timber is presently being researched. It takes around four to five days for the artificial seasoning of timber.

There are five methods for the artificial seasoning of timber.

Boiling

• Boiling the timber before utilisation gives it the necessary character traits for its particular use. 
• Using this technique, wood is submerged in water and cooked for three to four hours while being watched. The needed amount of sap in the water is removed during boiling.
• Instead of boiling, this procedure might be carried out by running the stream over the wood. Although boiling is a quick procedure, the energy it requires drains the economy. As a result, the procedure saves time but is expensive.

Kiln seasoning

• One of the popular methods used in the numerous industrial procedures for seasoning of timber is kiln drying. 
• Using external energy speeds up the driving out of moisture in this process, which speeds up the seasoning of the wood.
• The lumber is stacked here in a manner like that used in the air-drying process, and it is then put inside a chamber with the ability to change the environment to get the optimum seasoning results. 
• Depending on the need for seasoning, the kiln’s conditions can be modified.

Chemical seasoning

• This chemical seasoning procedure seasons the timber using high-value applications. Rifle butts, golf club heads, and carvings can all benefit from this treatment if the wood is fully free of surface checks.
• Chemical seasoning of timber, which involves dipping wood in sodium chloride or sodium nitrate solution, is often referred to as salt seasoning. 
• Salts like sodium chloride or sodium nitrate can pull moisture from a wood’s interior.

Electrical seasoning

• High-frequency alternating current is used electrically in the seasoning of timber by passing it through the wood. 
• When an electrical current is applied to wood, heat may be produced, which kickstarts the drying process.
• This process of drying lumber is done under the guidance of professionals to assure security. 
• The moisture content of wood decreases significantly, and electrical resistance rises as seasoning progresses.

Microwave seasoning

• Although it is not a common practice, microwave seasoning of timber can be used as an alternate tool to air dryers to assist and assure quicker and amazing wood quality drying.
• Pulsed microwave radiation is used to microwave season wood. It is directed into layers of wood to be seasoned to remove moisture from the wood at a frequency that preserves the seasoning.

 

Seasoning of timber: Significance

 

1. After seasoning, timber usually becomes stronger.
2. Timber that has undergone artificial seasoning will have sap that does not support the growth of fungus and parasites.
3. It is common knowledge that dry timber is less likely to rot.
4. The reduction in moisture gives seasoned wood various advantages.
5. When used in machinery, seasoned timber is safer.
6. Seasoned wood is considerably simpler to deal with since it has less of a propensity to split, tremble, or distort.
7. The weight of timber is greatly reduced after seasoning, making it easier to carry.

 

Seasoning of timber: Objectives

 

1. After the timber has been “seasoned,” its goal is to make it more durable so that the component’s design life will last for a long time.
2. Seasoning of timber is a cost-effective strategy for lowering shipping costs.
3. Having a check on insect damage and preventing rot before the timber is used is one of the crucial benefits of seasoning of timber.
4. Timber must have moisture to rot, period. The principle of seasoning may be used to keep wood or timber dry, which reduces the likelihood of rot.
5. The seasoning process prepares the wood for further industrial uses and the injection of preservatives.
6. Timber should not contract more than a certain amount after it is used for safety reasons. Timber that has been seasoned tends to shrink less.

 

How does seasoning of timber work?

Timber seasoning can happen outdoors or in specialised wood-drying kilns, providing optimal heat and airflow for effective drying—an essential aspect of the process. Timber is cut to size and stacked in these structures or in open spaces, ensuring adequate air circulation around each board. Depending on the environment, seasoning time varies. Outdoor drying takes 6 to 9 months to reach 25% moisture content, while kiln drying achieves this in a much shorter span, ranging from 2 days to a week.

 

Seasoning of timber: Precautions

 

1. Moisture content should be eliminated during the seasoning of timber.
2. Given that varied levels of dryness result in irregularly shaped logs, moisture should be removed from each one of them approximately equally.
3. During air seasoning of timber, seasoned wood should be kept safe from rain and extreme humidity.
4. A suitable space should be maintained between the logs during the seasoning of timber to allow for consistent and ample air, water, or hot air flow.

 

Qualities improved by seasoning of timber

Seasoning of timber improves following wood properties.

Hardness

When wet, the seasoning of timber makes it much tougher than it is. As flooring and furniture grow more resilient to damage from bumping and banging, it is advantageous even if it has drawbacks if you want to drive nails into seasoned hardwood.

Strength

After the seasoning of timber, a rise in strength is seen, particularly in tensile, compressive, and bending strength. Seasoning of timber also has an impact on stiffness.

This leads to the conclusion that structures built using wood with high service strength ratings get stronger over time.

Durability

Timber with a moisture level of at least 24% is more prone to develop rotting and staining fungus. It further softens the wood and resulting in unsightly stains.

Therefore, to preserve its life and prevent the look of the timber from degrading, it is seasoned and stored at a moisture content below 24% in a controlled environment.

 

Weight

An effective weight reduction is achieved by lowering the water content of timber from its initial green value to 10 to 15 percent. It helps with handling and brings down the price of transportation.

Adhesive

The quality of the wood also affects how well adhesives adhere to it. When the wood has been adequately seasoned, adhesives will form the strongest bonding. Bonding strength reduces because of moisture from a separating layer between the wood and the glue.

Finishing and painting

To achieve successful results, timber must first be “seasoned” before being painted, varnished, or polished. Due to the moisture concentration on the surface, failing to adhere to the seasoning routine may cause the surface coating to peel, crack, or blister.

Resistance to electricity

Seasoned wood has an approximately one in a million increase in electrical resistance. Undoubtedly, green wood with high moisture content is an excellent conductor of electricity, but dried wood acts as an insulator.

Resistance to pest-attack

In the case of unseasoned timber, insect attack is more prevalent. The variety of insect species that may attack wood is constrained in mature wood.

Insects are given preservation to help them fend off predators. In certain situations, partial seasoning of timber could be necessary to carry out such a process.

Heat Content

Certain types of wood are utilised for ignition, and for those woods to burn quickly, they must have a high calorific value.

Timber that has been season-treated has a calorific value of around 16 to 19 MJjk g, which makes it easier to ignite wood and burn it more efficiently while producing less smoke and reducing pollution.

 

Seasoning of timber: Advantages

1. Lower money investment is required in the seasoning of timber.
2. In Situations where market demands are uneven and weak, seasoning of timber can be a fruitful business.
3. Natural seasoning of timber does not require specialised work.
4. The regular seasoning of timber can significantly reduce flaws in the wood, like shrinkage, cracks, and wrapping.
5. The process of seasoning of timber is more efficient as it removes moisture content from the wood.
6. Pest attacks can be reduced using the seasoning of timber.
7. Finishing and painting wood can be done more effectively with the seasoning of timber.

 

Seasoning of timber: Disadvantages

1. Seasoning of timber needs large land for its processing.
2. Sometimes it is difficult to reach the desired amount of moisture content during the seasoning of timber.
3. Air seasoning of timber is a very long process that often takes 2-4 years since it depends on natural air over which we have no control.
4. Insect and fungus attacks cannot be prevented while the procedure is underway.
5. Processing costs are considerably high during the seasoning of timber.
6. Occasionally, trained staff is required for the seasoning of timber.
7. If there is less market demand for timber, seasoning of timber might be unprofitable.

 

Conclusion

The process of reducing the moisture content of the wood to the desired amount is known as the seasoning of timber. Strength, elasticity, and durability qualities are generated by lowering the moisture level in wood. A well-seasoned piece of wood has 15% moisture as compared to an ordinary log.

 

FAQs

Why is the seasoning of timber required?

Seasoning of timber before use is always a preferable option since it has the power to increase its strength, get rid of wood rot, and keep the timber's dimensions and form from changing.

What are the categories of classification of timber for seasoning?

Timber may be divided into the three groups depending on how it behaves in terms of cracking, splitting, and drying rate. Class A: High refractory woods, Class B: Moderately refractory woods and Class C: Non-refractory woods.