How to Straighten a Bowed Board: Woodworking Woes

Woodworkers are familiar with the fact of bowed wood boards that were straight before. Now, it may seem new to you as an enthusiastic DIY person. Hence, you end up asking yourself how to straighten a bowed board.

Well, the bowing of the board is not an unnatural thing. Rather, changing the shape and form of the wood board is very natural. However, the rate of warping or bowing varies depending on the environment and its humidity. So, you can straighten the boards by following some methods like using pressure or iron. Also, sunlight helps straighten the bowed board gradually.

Nonetheless, there are other many ways and methods of straightening bowed boards. Thus, to have a full-fledged concept about the topic, bear with us till the end.

StepInstructions
1Determine the bow: Lay the board flat on a level surface and check if there is a bow by sighting along the length of the board. Mark the highest point of the bow.
2Secure the board: Clamp the board onto a workbench or sawhorses.
3Make a kerf cut: Use a circular saw or hand saw to make a kerf cut along the length of the board at the highest point of the bow. The cut should be about 1/3 to 1/2 of the board’s thickness.
4Moisten the board: Dampen the concave side of the board with a wet cloth or sponge.
5Apply heat: Use a heat gun to apply heat to the concave side of the board, moving the heat gun back and forth along the length of the board. Keep the heat gun moving to avoid scorching the wood.
6Apply pressure: Use a clamp or weight to press down on the board at the highest point of the bow. Keep the pressure applied until the board cools.
7Check the board: Remove the clamp and check the board for straightness. If the bow is still present, repeat steps 4 to 6 until the board is straight.
8Sand the board: Sand the board to remove any saw marks or rough spots.

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Why Woody Board Bowes?

Before it makes you utterly surprised, you should know the science behind the boards becoming bowed. Otherwise, you would never know the prevention methods as well. As a result, storing wood boards would become difficult for you.

Well, the reason is obvious since wood is supposed to change its shape constantly under humidity. However, the changes depend on the humidity level in the atmosphere. If the air contains high humidity, then the boards absorb the moisture in their surface pores from the air.

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When the wood fibers absorb moisture more than they need, they start to swell. As a result, the board gradually starts to expand and deform its size.

Then again, when the environment is dry, air sucks the moisture from wood pores. This thing is also responsible for changing the shape of the board. As the wood release moisture, the size of the fibers of the board also shrinks. Consequently, you get a bowed and warped board.  

However, the board does not shrink or swell at the same rate always. As we mentioned earlier, it depends on the amount of humidity present in the air. Nonetheless, it also depends on the way of storing and the thickness of the board.

The thinner the board, the more it will bow and warp. Thin boards are less resistant and warp faster. Then again, if you put the board in a way that one part of it is more exposed to moisture than the other part, then you will find the exposed part is bowing by forming a C-shape figure.

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How to Straighten a Bowed Board – Discussion of Methods

How to Straighten a Bowed Board
Woodworking Woes Heres How to Straighten That Bowed Board

You simply cannot work with bowed boards even if it happens in a small place of the entire board. A proper straight board will ensure a great result. Thus, knowing the flattening process when your board is bowed is a must.

  1. Moisture and Steam

This is the most common way of flattening bowed wood boards. Many woodworkers out there follow this method as it is highly effective for bow warp wood. moisture and steam can unwarp wood the same way they warped the board previously.

In this method, first, heat the board slightly for about 12 to 15 minutes. Then add moisture to the board. The hot wood board will absorb the moisture quickly. Hence, make sure you are applying added moisture to the wood.

When the board absorbs moisture, it becomes flexible as well. consequently, the board bent back into its previous straight shape. Now, when the board straightens, clamp it to a flat surface and let it dry straight.

  • Pressure
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You can apply pressure to straighten the bowing board. But you need to create pressure in the right place. It may also take some time to straighten as the process is time-consuming. So, people with enough patience can apply this method by following the below method.

First, moisten some paper towels and cover the board with them. arrange the sheets over the surface where the board is curved inwardly. That means to cover the concave portion very well. It directs the bow portion to flatten like the previous way. However, you can also use thin steaming towels. But make sure they are moistened well.  

Second, wrap plastic wrap layers over the paper towels very tightly. The plastic will not allow evaporation from the towels and board for a long period.

Now, place your board in a clamp. Over-tighten the clamp so that the bowed place of the wood starts to flatten slightly. Again, be careful with the tightening process. If you tighten the clamp too much, it may end up splitting the board.

Then, leave the board clamped for at least a week. However, make sure you keep the board in a warm area of around 65 degrees Celsius if possible. Again, you can use a heat lamp or electric blanket to create the optimum temperatures. You should allow the heat for about 6 to 8 hours a day.

Finally, after one week when the board straightens, remove the clamp, plastic wrap, and paper towels from the wood. Then let the board dry.

  • Sunlight

Sunlight intensity can also flatten a bowed board. However, this is another slow process and is usually not recommended. Yet, it works somehow if you follow the right method.

For this method, you also need moistened towels to wrap the wood board. Use large towels to cover the entire board. Then place the board in a place where it will get direct sunlight.

Keep the inwardly bent or the concave side opposite the sunlight whereas, keep the outwardly bent or convex side facing the sun.

Make sure to adopt this method only when the weather is warm and dry during the day. This method will not work in aa cloudy, cool, or wet environment.

Keep the board under sunlight for about two to four days. Meanwhile, keep spraying the towels with water so that they remain moistened throughout the whole time. Keep the board under sunlight until it straightens completely.

  • Ironing
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Using a pressing iron is another way of straightening a warped wood frame. For obtaining this method, however, you will need towel or cloth pieces that are wet, an ironing table, and obviously, an iron.

So, first, soak the towel or cloth pieces with water and squeeze them properly so that they are not drenched anymore. Now, cover the bowed area of the wood frames entirely with damp pieces of clothing.

Then place the frames on the ironing table. Now, heat the iron and press it over the moistened towels that are covering the frames. Press properly and moisten the clothes properly if they dry in the process. Keep continuing the process until the wood frames get straightened properly.

  • Jack Plane

Using the jack plane is another method but it may bring some risks. Also, it may not that much effective on the bowed board. However, if the board is bowed in a small portion, then you may apply this method.

Nonetheless, the method includes removing the bowed part from the board by using the jack plane. Removing the part will straighten the surface. But many get overwhelmed with the process and cut a large part of the board making it weak. So, you have to be careful with this process.

Preventing Wood Board from Bowing

However, there are some ways to prevent your boards from bowing in the first place. So, you can follow them to lessen any hassle.

  1. Inspecting Wood

This is the first thing to do when buying wood because wood quality matters a lot. If the wood quality is poor, it will surely bow in no time. Hence, make sure you are buying wood of the best quality.

Again, make sure the wood is containing the right amount of moisture in it. You can also use a moisture content detector to inspect its moisture level.

  • Storing Properly

As we mentioned earlier, improper storage is one of the reasons why wood bends or wraps. However, the best way to store wood is to lay it flat. Keeping wood standing may induce its bending.

  • Make the Wood Moisture-proof

We know that moisture is mostly responsible for the bowing of the wood. Hence, to overcome this problem, making the wood moisture-proof may help.

However, the best way to make the board moisture-proof is to coat the wood surface with a polyurethane finish. Again, you can use any oil-based paint. These finishes create a layer over the wood surface and work as an insulator. Hence, moisture cannot get into the wood and affect it.

  • Do Not Dry Out the Wood

Yes, the wood should contain a certain amount of moisture in it. Thus, let’s not dry the wood board completely. Otherwise, the fibers of the wood will dry out and make the board bend.

FAQ

Can you straighten bowed wood?

Well, it is possible to straighten bowed wood even if a large area has bent. You just have to pick the right method. Pick any of the methods we have stated above and follow them carefully.

How do you straighten a warped 2×4 board?

You can straighten a warped 2×4 board by following the ironing method. Keep pressing the iron over the damp cloth that is coving the board until it gets straightened.

Can you straighten a twisted board?

Twist warping of the board can take place due to storage issues. However, you can straighten a twisted board if you ensure an even dry out of the moisture the board has absorbed.