Wood defects like warping deform the wood and make it challenging to use for your projects. Bowing is a popular type of wood warping where the wood ends are raised while the center remains depressed. Bent boards affect the shape of furniture, lockers, and more with more difficulty when building with such wood. The problem of aligning the panels is also an issue you’ll face with warped lumber.
When wood bows, it deforms into a C-shape, depending on the angle from which you’re looking. Most woodworkers abandon the board and seek new ones, which can be expensive. It’s why fixing bowed wood is an essential skill every woodworker should possess.
As it becomes clear why repairing bowed wood is vital, more people seek information on techniques, considering mistakes can damage the wood or even cause injuries to the woodworker. Let’s consider ways to fix this now and return the wood to its flat structure.
Table of Contents
Reasons Why Wood Can Become Bowed
Wood can bend for many reasons, with environmental factors among the leading causes. However, the combination of ecological factors and human negligence often makes boards bow. Before considering the various methods to straighten bowed wood, we must know the cause of it all to prevent further damage.
1. Grain Orientation
The grain style and position can cause bowing, especially when this orientation is not considered during cutting and usage. Some cutting tools require specific techniques to shield the grain orientation and prevent bowing.
Different board types also demand specific actions during usage that help its characteristics. One such board is the flat-sawn wood that expands and contracts with environmental changes. So room should be left for such changes when using it for building.
2. Improper Storage
Lumber to stored before use, but the process is the leading cause of the deformity, as most woodworkers employ poor storage techniques. Exposure to sunlight or frequency changes to the humidity is a quick way to a bowed board as the wood struggles with constant expansions and contractions.
3. Growth Pattern
An irregular growth pattern will quickly spiral into warped wood, with this cause often happening before the woodworker gets the wood for use. Some trunks bend while growing as they thrive for air and sunlight and already come with bowed structures. You can avoid defective boards beforehand by paying extra attention when purchasing wood or cutting wood curves.
4. Uneven Drying
Wood must dry evenly and slowly as sudden changes can make it bend and deform shape.
To ensure the boards dry slowly and evenly, keep away from direct sunlight while ensuring the air source for drying is controlled and reaches all parts of the wood equally. Using wet wood will also cause the wood to bow, losing water even after completing the project.
5. Moisture Imbalance
Moisture in wood is a sensitive factor as it can quickly become a problem, so you want to pay extra care with the board’s moisture content. Higher humidity on one side can quickly cause bowing as the dryer side stays the same while the wet wood section expands and then curves.
The same can be said during drying, with moisture content in wood requiring equality for the wood to remain straight. Keep moisture away from already dried straight wood to avoid dealing with moisture imbalance in the lumber.
Age is another factor that is out of your control as wood deforms with age as all the different factors it has been exposed to start to affect it. As wood ages, they naturally shrink or expands in some cases, which can cause bowing in a gradual, often unnoticeable process.
7. Physical Force
When external pressure is applied to wood, it deforms and warps. Even though wood has a strong structure, it can bend when heavy objects are placed on them, mishandled during transportation, or when a bending force is applied without proper preparation.
Preparing The Wood For Straightening
Repairing wood often requires a lot of external pressure, depending on the method employed. By preparing the wood for this force, you’ll make it easier to fix and also prevent injuring yourself or damaging the board. Lack of proper preparation for wood bending will only aggregate the issue with more bowed or even outright cracks.
Identify the type of wood and determine if it is favorable to bending. Flexible woods are easier to fix and have lower chances of splitting. You should also check the bow’s severity, as certain bends are challenging to reverse, and it is better to use new lumber rather than trying to fix the bowed board.
After identifying the wood as suitable for bending and the bow as mild, you can go ahead with softening the wood so it doesn’t break when fixing. Use a combination of heat and moisture on either side of the board to get it ready for straightening. Lightly sprinkle water to one side of the wood and warmth to the other while ensuring an even spread.
Step-by-Step Guide For Straightening Wood
After the preparation, your wood is ready to be fixed; however, the method you choose and its execution will determine its success. Here’s how to straighten bowed wood:
Step 1: Identity Concave And Convex Sides
Start by observing the wood to identify the internally bowed concave and outward convex sides. This information is essential to fixing the curve as it allows you to apply the right amount of pressure to the correct wood face.
Step 2: Apply Heat or Moisture
You can either reduce or increase the moisture content in the wood by applying heat or adding moisture to repair the wood. The idea is to put the wood at an optimal level with a good moisture level which is why heat is applied to wet wood and moisture is used to dry wood.
Remember, an even application is required as heat and moisture can cause bowing without equal distribution. Heat guns and a spray can are the standard tools for this process.
Step 3: Straighten With Clamp or Weight
The wood is ready to be bent with external forces at this stage. You’ll need a straight worktable to provide a guide for the bowed lumber. You’ll also require a means to apply pressure and bend the wood with tools like clamps, straps, or weights preferred.
With the concave side of the board facing up, it is easier to bend without breaking the wood. Use a combination of clamp and weight to fix this by calling the board around various parts and placing even weights on the board. You want to ensure the weight is even on all its sections and is not too much that it causes a depression in the wood.
Ensure gently applying the pressure with the clamps as sudden force applications can splinter wood. Also, slowly add the weights to the wood to aid in straightening.
Step 4: Allow The Wood Structure to Stabilize
With the heat and moisture combination done to soften the wood and the pressure applied using clamps, the wood structure is in disarray and requires stabilizing. After removing the clamps from the now straight lumber, you mustn’t exert any pressure on it yet or use it for any project.
Keep the wood for some days in a location with optimal storage conditions. This period steadies its structure, allowing it to harden. The stabilizing process is essential to prevent the re-bowing of the wood.
Step 5: Assess The Wood
Fixing bowed wood can take up to several weeks and will require constant observation to avoid further damaging the wood. After a few hours, remove the weights and the straps or clamps and observe the board.
For straight boards, move to the next step; however, if it is still bowed, you should replace the clamps and weights for a few more hours before removal. Slowly add force and weight if the wood is not straight after the first try.
Finishing The Wood
Use a sander with a 120-grit sanding capacity to smoothen the wood, as the addition of moisture during its preparation stage has raised its grain. However, you want to only lightly sand the wood as heavy sanding significantly reduces wood thickness.
After achieving a smooth surface, you can apply your desired paint or stain to the wood and use it for projects. Always follow the correct application style to get the best look.
We understand that many woodworkers have questions about the whole process, so we went ahead to compile common questions and answered them.
Ans: Time to straighten bowed wood is flexible and varies depending on the technique employed and the bow level in the wood. Straightening bowed wood could take a few days to several weeks.
Ans: Applying too much pressure can break the wood, mainly if proper preparation to soften the wood is neglected.
Ans: Where wood does not straighten entirely due to a severe bow, you should determine if the now is slight and usable, or you should replace the lumber.
Ans: To prevent the wood from re-bowing after fixing the bow, here are a few tips to follow:
• Store in stable conditions and avoid frequent atmospheric changes
• Dry properly and keep moisture away
• Utilize fastening methods that give room for the board’s expansion and contraction
If you want to fix bowed wood like a pro, you must understand why wood bends so you can prevent a further recurrence. Another process that boosts the success rate and prevents wood damage is the preparation stage, where the wood is softened.
Applying pressure using clamps and weight is the ideal way to fix bows in wood; however, severe warps are challenging to repair and may require an outright board replacement.