The issue of warped wood is something that concerns those who work with wood at all levels. When wood warps after being installed the wood can become misshapen, leading to a lot of extra work and complaints. Warping in the case of structural wood can even be a safety hazard. It is important to understand why wood warps and what you can do to prevent it from occurring.
In this post, we have identified the most-common wood warping FAQs and compiled them here. You can use this information as a ready-reckoner to help you with your woodworking projects. Once you understand the dynamics of wood warping, you can take due precautions to minimize this occurrence
- Wood Warping FAQs
- What is wood warping?
- What are the types of wood warping?
- What are the factors that affect wood warping?
- How can we prevent the wood from warping?
- Is it possible to fix warped wood?
- Can we use warped wood?
Wood Warping FAQs
What is wood warping?
Wood warping occurs when the wood dries unevenly, giving off different levels of moisture at different spots. The result is that the shrinkage in the part that dries faster tends to distort the shape of the wood. The flat surface of the wood becomes twisted or curved. We call the process of distortion of wood, warping. Wood warping is a common issue amongst all those who deal with wood and affects all varieties of wood products from furniture to musical instruments.
What are the types of wood warping?
There are five types of wood warping:
- Bow: The wood bends along its length curving the thinnest face.
- Crook: The wood bends along its length curving the thicker face.
- Kink: The warp occurs along the width of the lumber creating a kink
- Cup: The wood warps in a cup-shaped curvature.
- Twist/wind: The corners of the wood get twisted so that they are not on the same plane.
What are the factors that affect wood warping?
There are a few factors that cause wood to warp. A few of them are as follows:
Equilibrium Moisture Content (EMC)
If the wood has absorbed moisture to its full capacity, it will neither release moisture nor take in moisture. In this condition, it will have a stable shape and will be ready to use or ship.
The temperature has a direct impact on the way wood takes in moisture. Hence, wood tends to acclimatize faster in hot weather and the process slows down when it’s cold.
Thicker wood is less prone to warping and vice-versa.
Some wood species are more prone to others. You can get a lot of information from the United States Department of Agriculture (USDA) wood handbooks.
Grain orientation refers to where the wood was sawn. For instance, wood that comes from the heart of the tree has the tightest grain structure and has the least tendency to warp.
How can we prevent the wood from warping?
This is the easiest and most straightforward step to take. Try to select wood with a straight grain and of course, wood that isn’t warped already.
You need to stack your lumber correctly and provide enough ventilation. You can use “stickers” which maintain a gap between boards. Store your lumber on a flat surface to prevent wood from warping.
Understanding wood grain is a bit complicated and needs experience. Wood has less or more tendency to warp depending on the way it is cut. Rift sawn wood has the least tendency to warp but creates more wastage than flat sawn wood, which is more prone to warping. Flatsawn wood is, however, the commonest form of lumber.
Is it possible to fix warped wood?
It isn’t easy to fix warped wood, but yet, it is possible. The basic principle behind rectifying warped wood is in two steps. First, moisture is re-introduced into the wood. Then, the wood is clamped and made to dry in a flat orientation.
To add moisture, we spray or soak the wood with water. Later the wood is clamped and we need to let it dry. We can dry the wood by applying heat or it can be left to dry naturally. There are a few devices that we use for fixing warped wood.
The first is a regular iron. A paper or cloth is dipped in water and placed on the warped section. Then, wood clamped on a flat surface and iron is placed on it. This process is repeated for as many times as it takes to remove the warping.
The other device is the steam machine. The steam machine is specially designed to straighten warped wood. It contains a tank in which water is boiled and steam generated. The steam is directed onto the warped surface once the wood is clamped to a flat surface.
A third device is the ironing machine. It involves using a similar process employed with the steam machine, but in this case, the machine heats the wood directly. During the heating process, we put a wet piece of lumber on top of the heated metal surface. The wet lumber creates steam and helps the wood to relax.
Can we use warped wood?
Sometimes it isn’t required to fix warped wood, because it doesn’t matter too much if it is warped or not. But this depends on what you intend to use the wood for. For example, if you have warped wood but you will screw it to other parts, then perhaps it doesn’t matter whether the wood is warped or not.
Also, if the warped sections are rather long, then it is possible to cut off the warped sections or cut it in such a way that the warping doesn’t show too much. You will probably find a use for your cut bits in the future.
Wood warping can have a major impact on a woodworking project. Even end-users face the issue of wood warping. I remember once when I was a young boy, I left a guitar out in the sun for a few hours. The wood became warped beyond repair. At the time, it bewildered me. How could such a thing happen? But you can easily see why it happened by using the information we have provided here.
Wood warping can occur at any stage of wood processing – from the lumber yard to the finished product. Although we can’t always prevent warping, we can minimize it by taking adequate precautions. Now hopefully, your questions regarding wood warping should be answered. You should be in a better position to deal with wood in your woodworking projects with regards to warping.
Featured image by JerzyGorecki