Is Wood a Pure Substance?

Wood is possibly the most versatile material. It can be made into homes, furniture, and other wooden items. It is raw material for many products and can be processed to make clothes, packaging materials, paper and more. But what is wood really? Is it a pure substance? This guide will tell you exactly what wood is.

Is wood a substance?

Wood is a mixture or better yet, a heterogeneous mixture. This is because all the elements and compounds found in a piece of wood are not evenly distributed throughout the body of the wood.

If you were to get a sample of wood from different parts of a tree, you will find that one sample is different from another.

A sample may have more water or oxygen than another area. Another sample may have tree sap while some may have none. Different elements and compounds are found in varying levels in a mixture and this is what happens in wood.

What is wood made of exactly?

Wood is comprised of cells and only the cell walls have specific gravity. Cell matrices inside wood vary in shape, size, and arrangement. Similar to a sponge made of lignocellulose which has lower specific gravity than the theoretical maximum due to the amount of space in the matrix which is filled with air and water.

Wood is very similar to sponge because most kinds of woods are able to float in water and have specific gravities with values less than 1.0. There are a few tropical hardwoods that are heavier than water and will sink.

The known heaviest wood in the world is lignum vitae (Guaiacum officinale) with a specific gravity of 1.05 when it is still green. However green wood has a moisture content from 30% to over 200%. Because there is a lot of water inside the wood chambers, this wood is unfit for burning and even for construction. Wood has to be seasoned or dried well before it can be used completely.

Comparing earlywood and latewood

Wood undergoes developmental stages in its lifetime thus it can be called earlywood or wood that is in its early stages of development and latewood or wood during its later stages. Wood retains its physical and chemical makeup throughout its lifetime but there are stark differences in moisture levels.

When wood is earlywood its cells are created during the fast-growing early weeks of its development. This is when moisture is at its peak levels and is higher with thinner cell walls. This allows improved flow volume of different minerals in and out the wood. But as wood enters its late stage of development, its growth slows down as well and wood takes on a denser form with thicker cell walls and smaller cell lumina.

The weight of wood

Wood is a mixture of organic materials, air, and water. As mentioned, it is a homogeneous mixture because the materials or components are found in varying concentrations in the wood body.

So with this information, how do you find the actual weight of wood or only the wood’s organic body?

It’s quite complicated to measure the exact weight of wood because of the specific gravity of wood changes with its moisture content. Once the moisture of wood goes below 30% then it starts to become lighter. It is at 30% the fiber saturation point of wood happens. Higher than this percentage and you get wood that is full of water with water slowly bonding with the material of the wood.

When moisture content in wood becomes less than 30%, all the free water has evaporated and the bound water starts to be removed from the material. The cells of the wood start to shrink which is actually what happens in a sponge out of the water. The specific gravity of the wood also increases and the wood begins to stiffen. Wood still retains its homogenous mixture state despite moisture leaving the wood at a rapid rate.

Conclusion

Wood is not a substance but a homogenous mixture. It is a combination of different minerals, organic material, and water but in varying levels all over the wood body. Wood has a high percentage of moisture during its early stages and slowly, moisture escapes the material as it enters its late stage. But despite this, wood retains its homogenous characteristics.

  • December 29, 2018
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