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Humidity and its effect on various species of woodFeatured science projectScience project video


This science fair project was conducted to determine the effect of atmospheric moisture on different types of wood. The science fair project was done by comparing the effect of moisture on redwood, teak, black oak and red maple wood.


Humidity will cause different types of wood to expand and shrink at different rates.

Scientific Terms

Moisture, expansion, contraction


Expansion and shrinkage in woods

Trees contain water just like any other living organism. A freshly cut piece of wood has higher moisture content and is not suitable to be used as firewood nor is it suitable for woodworking purposes. These newly cut pieces of wood must first be dried in an oven or in an open space. The ideal condition of the wood is said to be achieved when there is a level of equilibrium in the humidity between the wood and its surrounding environment.
Wood tends to expand and contract. This is actually caused more by the changing humidity surrounding the wood rather than by thermal factors. A higher atmospheric humidity will cause the wood to expand while a lower humidity will cause the wood to shrink.

Changes in the dimensions of the wood are normally higher along its growth rings while the changes in the dimension of the wood along its length are normally negligible.
How much a certain species of wood changes in its dimensions by expanding or shrinking according to the surrounding humidity cannot controlled. Experienced wood workers and carpenters need to effectively understand this behavior of wood in order for them to effectively plan and implement projects.

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Complexity level:
Project cost ($):
Time required:
1 day to prepare, 1 day for observation
Material availability:
Easily found
Safety concerns:

The oven should not be left unattended when the pieces of wood are left to dry in the oven for 24 hours. There is a possibility of the wood catching fire (although it is unlikely, if a proper temperature setting is used). Have fire safety equipment on standby. Be careful when removing the hot wooden blocks from the oven. Use gloves for protection.