How to Harden Wood for Painting or Staining? (7 Ways)

hardening rotted wood for painting

While wood is highly popular for many projects, it is also subject to rot, invasion by pests, damage due to moisture, and mold or mildew that may follow.

And when it’s time to refinish, softer and damaged wood won’t take a finish well. If you still try to paint or stain it, the finish won’t look right and will quickly peel. Hence, to avoid this problem, it is necessary to harden the wood so that it can bear heavy brush strokes and other finish elements.

By hardening the old wood before painting, you can restore it to keep it close to its original condition for many years. Not only does the hardened wood looks great upon finishing, but it will also be well-preserved and more resistant to the elements thereby last much longer.

However, the downside is that the wood hardening can only be used for timber that has just begun to soften or rot. So unfortunately it won’t fix pieces of lumber, floor, or furniture that are too far gone, can break apart easily, smell bad, and contain bug infestations.

Different Methods to Harden Wood

There are different methods that can be used to harden the wood. What follows are descriptions of each method and how to apply them.

No matter which one you choose ensure to work in a well-ventilated area and follow the instructions carefully.

1- Polycryl Wood Fortifier

Polycryl is a wood fortifier, an adhesive that forms a strong chemical bond with the wood surface and not the underneath wood fibers.

It’s also inexpensive, readily available, and can be easily used by reading the instructions. You will need the following items to start with:

  • Polycryl
  • Gloves
  • Water & Bowl
  • Old or Disposable Paintbrush

Clean: Start by cleaning the wood surface so that it is free of dust, dirt, and debris. Otherwise, such particles will stick once the Polycryl is applied. Before you proceed ensure the wood is fully dry.

Prepare: Polycryl fortifier is highly concentrated and should be diluted as per the label’s instructions (in a recommended ratio) before it can be applied. Pour the Polycryl into the water bowl and stir until it forms a thick liquid.

Apply: Now spread and apply this thick Polycryl liquid across the surface of the wood in generous portions with a disposable paintbrush. You do not have to highlight weaker areas; simply cover the entire surface as evenly as possible.

Dry & Check: It normally takes about five hours for the Polycryl to dry fully, but check with the manufacturer’s label to get an exact idea. Once dry, check to see if the wood has hardened. If you are not satisfied with the results, apply another coat of Polycryl.

Protective Finish: Use a wood lacquer or varnish to protect the wood that has hardened. Applying the finish right will provide an extra layer that keeps the wood hardened for a long time by protecting it against both water and the UV rays of the sun.

2- Epoxy Resin

One of the more popular methods for hardening wood, especially softwood, is using epoxy resin. This keeps the loose fibers intact and hardens the surface to a considerable degree.

Of the many different types of epoxy resin on the market, you should use the one that is the hardest for the best results, particularly if the wood itself is brittle.

To get started purchase the following:

  • Epoxy resin
  • Water
  • Disposable Applicator or Bristle Brush
  • Safety Mask & Gauntlets
  • Putty Knife

Since epoxy releases toxic fumes, set your wood hardening project up in a well-ventilated area, preferably outside if you can. Or put a fan in the room with open windows if the outside is not an option.

Clean: Clean away all loose dirt, dust, and debris, and use the putty knife to scrape out all the loose wood fibers from the crevices. Take some time to do it well, otherwise, any remaining loose fibers will prevent proper bonding with the epoxy resin.

Mix & Apply: Most epoxy products consist of two separate materials, the epoxy, and the hardener. While there are some epoxies that can be mixed with water. Whichever you choose follow the formulation as part of the manufacturer’s label.

Apply & Drill: Pour the mixture onto your wood surface and use a paintbrush or a putty knife to spread it evenly.

If the wood is either too thick or soft, to get the results you want from the hardener product, drill a hole in the middle of the wood and add the epoxy mixture inside. Performing this extra step will harden the wood to an even greater degree as the epoxy spreads into the wood fibers.

Dry & Reapply: Let the mixture dry for about three to four hours, or follow the drying times listed in the instructions manual of the epoxy strengthener. The smaller the surface is, the faster will be the drying time.

Once dry, reapply with more epoxy layers if the wood project still requires it. You may need to drill more holes as well to ensure full coverage of the epoxy resin. When you have added the last layer of epoxy resin, let it cure for at least three days.

3- Wood Hardener

If you have old rotted wood, you can make it tougher using this simple yet effective chemical treatment product. To use this method you will need:

  • Wood hardener
  • Soap & Water
  • Putty or Carving Knife
  • Gloves and Face Mask
  • Pressure Sprayer or Paint Brush

Liquid wood hardener is available in a variety of colors and stains, including brown, red, yellow, and several others. You may also get clear wood hardener products if you wish to have a more natural finish.

It’s entirely up to you whether or not you buy a product with color; if you do, make sure it matches the surrounding wood; things should match and appear similar.

Some of the best wood hardeners that I could recommend include:

  1. Elmer’s Rotted Wood Stabilizer
  2. Minwax 41700000 High-Performance Wood Hardener
  3. PC Products PC-Petrifier Water-Based Wood Hardener
  4. J-B Weld 40001 Wood Restore Liquid Hardener
  5. Bondo Rotted Wood Restorer

Once you have your product, here are the steps to follow…

Prep the Wood: Use the carving or putty knife to scrape away the loose debris. Then using soap and water clean out the particles from the decayed part of the wood and let it dry.

Prep & Apply the Wood Hardener: Stir or shake the hardener that normally comes in a can or bottle. Once ready, use an old paintbrush, roller, or pressure sprayer to apply the hardener to the surface until it’s fully saturated.

Dry & Reapply: It normally takes an hour to two for the first layer to dry. Once dry, reapply with a second and third layer. You can add up to five layers if you desire to get the best results with your wood stabilizer product.

Cure & Scrape Gently: Once you have added the final layer, let it fully dry, which may take up to 12 hours. When dry, use a wire brush to scrape away any excess wood hardener gently.

The thing you need to be cautious about is to act fast, as it can start to get hard and set in as little as 60 seconds. Once it has soaked in completely and dried, the deeply sealed wood will be significantly stronger and more resistant to further damage and rot.

4- Fire Hardening

Perhaps the oldest method to harden wood is by using fire treatment.

It may not sound practical at first to harden delicate softwood with firing. But the process itself is quite sound and it tends to work great for small pieces of wood when the heat from the fire removes the excess moisture, which in turn tightens the wood fibers.

However, with this process, you have to be extra careful to stop not only burning the wood but burning yourself in the process. This means having some water or a fire extinguisher nearby just in case the worst should occur. Also, you will need the proper protection, which includes safety gloves and goggles.

To start with get a source of fire which can be charcoal or wood. Plus, a way to ignite it. Here are the steps to follow:

Prepare: Having a fire pit to provide the heat is a must with this method. If you do not have one, dig a firepit about six inches deep and two feet in diameter. Surround it with rocks to prevent the fire from escaping.

Ignite: Put in the wood (or charcoal) and lite it up. Feed the fire until it grows sufficiently to generate enough heat. The flame should be a half-foot in height with a blue center to work.

Heat the Wood: Hold the wood about three inches above the flame and keep it moving for no more than 60 seconds. The goal is to apply the heat to remove the moisture but not scorch or burn the wood. So, it’s essential to check frequently to ensure that the wood is not being burned.

When the wood appears dull and feels tougher, it means the moisture has been removed. but if you are unsatisfied, reapply the heat one more time. Once done, let the hardened wood cool for about ten to fifteen minutes, and it will be ready to use for your project.

5- Wood Infusion with Resin

Many woodworkers and construction workers do not know that acrylic resin can be infused into the wood to harden it which is much safer to use compared to other materials.

The downside however is that the method of infusion can be difficult. But still, if you follow the steps it can be done without creating any mess. You will need the following:

  • Acrylic resin
  • Aluminum Foil
  • Shop Oven
  • Vacuum Pump & Chamber
  • Gloves, Goggles, and Face Mask

Dry in Oven: Use your standard oven to dry the wood by baking it at 250 degrees F for 3-8 hours, according to its size. Keep the temperature steady as increasing the heat can burn the wood in the oven.

Cool & Place in Vacuum: Let the baked wood cool and then place it in the vacuum chamber. If there are many small pieces of timber, ensure they are properly spaced and your vacuum chamber is big enough to accommodate all the pieces.

Add Resin and Create a Vacuum: Pour the resin letting all the pieces submerge completely inside the chamber.

Begin extracting air from the vacuum chamber to create a hermetic seal. You will see some tiny bubbles and froth in the resin as the air escapes the wood. The foaming should diminish as more air disperses away from its host material.

This complete process may take around half an hour or more, depending on the size and thickness of the wood. Once there is not a single air bubble left in the vacuum chamber, that signals the wood has entirely soaked up every bit of resin.

Let the Infused Wood Sit: After the above stage of stabilizing the wood is complete remove the pieces from the vacuum chamber and let it sit for a few minutes. Subsequently, eliminate and dry the resin off the wooden surface with paper towels.

Bake One More Time and Allow it to Cool: Once done, wrap each piece of wood with aluminum foil with the shiny side on the inside and then place it into the oven. The oven should be preheated to 150 to 200 degrees F, and the wood should bake for about an hour or two.

Once that time has passed, pull out the wood pieces from the oven and let them cool to room temperature while the pieces are still wrapped in the foil. After the pieces have cool down, take off the foil and remove the excess resin from your wood. Your pieces are now hardened.

process to harden wood with resin

6- Using Natural Oils

This is one of the simplest methods, but it also takes the longest time. So, if you’re looking for a quick fix and your project is on a fixed deadline, this isn’t the right process for you.

But if you can wait, natural oils like Tung or Linseed oil works quite well in hardening softwoods naturally. All you need to do is saturate the wood with the oil and let it sit for at least a month or more.

The oil will seep inside the wood pores and create a hard polymer (upon reacting with oxygen) that will form a barrier to moisture. This will also harden the wood considerably and for a long time.

7- Wood Epoxy Consolidant

Abatron’s LiquidWood® epoxy wood consolidant is an easy-to-use product that is known to produce fast permanent results when it comes to fixing deteriorated wood, floors, and structural damages.

By penetrating wood fibers from deep, it helps to structurally harden the decayed and weathered wood surfaces permanently.

The good thing about this product is it can be used to restore the wood both indoors (for your floors, panels, furniture, artwork, etc.) and outdoors (for your decks, beams, columns, windows, boats, etc.).

With this product at hand, you can literally fix any kind of wooden architectural element that has undergone wear and tear due to age, extreme weather conditions, or insects.

Ingredients:100% epoxy solids
Color:Translucent amber color liquid resin
Nature:Waterproof, Pourable, GREENGUARD® Certified with virtually no VOCs
Application Method:Apply by brushing, pouring, or injecting directly onto dry, bare wood
Application temperature range:50-90° F; cold weather formulation is also available for application temperatures as low as 35° F
Coverage:231 cubic inches per gallon, effective coverage, however, can vary based on the porosity of the wood.
epoxy wood consolidant

Homemade Wood Hardener and Consolidant

Old softened wooden surfaces can also be given a makeover by creating your own DIY wood hardener with just salt, water, cornstarch, and an egg white.

If you are too wary of using chemical-based substances in your home for minor repairs, you can use this method without any worry.

  • Start by combining the liter of water with 350g of salt until it’s fully dissolved.
  • Then add some cornstarch to thicken things up
  • Finally, stir in one egg white for that perfect consistency – you’ll know it’s ready when it’s spreadable using an applicator brush.

Not only on the old timber, but you can also add durability to your new boards with just a few coats of this homemade wood hardener. Applying this wood consolidant beforehand keep your wooden surfaces from becoming warped or damaged due to moisture damage.

Can Wood Stabilizer Be Applied to Wet Wood?

Irrespective of what wood-hardening product you choose – the short answer is no, you should never apply it to wet timber.

Wood hardeners or wood stabilizers are products that are designed to be applied to slightly moisturized wood or dry wood. This is because the product needs to be able to penetrate the wood in order to work properly.

Attempting to apply the product to wet wood will likely result in a poor bond, as well as a waste of the product. Moreover, it can continue to rot the wood from the inside out. So, if you’re working with wet wood, make sure to allow it to dry thoroughly before beginning your project.

Additional Ways to Reinforce the Wood and Keep it Strong

If you have aged and deteriorated wood that needs some extra support, maybe you will require to reinforce the wood and keep it strong for a long time. This is especially important if the wood is used around children or pets or if it’s under the force of gravity and a lot of use.

Here are a few different ways to fortify it…

1- Use wood glue

Wood glue works wonders for wood surfaces, forming a hard shell that fortifies the wood and seals its edges from harsh elements. It can also be used to repair rotten parts of wooden structures as well as bind pieces together.

The unparalleled protective qualities of this adhesive make it ideal for any DIY job. You can use it in a combination with wood filler to strengthen the wood even further.

2- Dry the wood and store it properly

Extracting the moisture from wood is crucial to preserving its strength and preventing warping if you plan to store it for a long somewhere safe. You can do this at home or in a factory with a kiln, and drying oven. But where you store your spare wooden pieces plays an important role in their longevity as well.

Keep them safe by storing them away from direct sunlight and dampness, putting racks below for elevation which will also prevent overly close contact of different slats with each other.

Then cover it all up securely during winter months when temperatures tend to fluctuate wildly. Otherwise, the wood may expand more than expected leading to permanent damage.

3- Use metal plates, brackets, and braces

If you have weak, rotten, or softer wood spots on a piece of furniture, reinforce it with metal plates. It may not be the most aesthetically pleasing solution but is highly effective – simply screw the plate onto solid wood joining both pieces and eliminating any potential weaknesses.

Alternatively, install braces or brackets to enhance delicate parts; attach them to the back of your item for additional structural strength without ruining its outward appearance.

Other than the above, you can also use plywood, 2×4 dimensional lumber or any other type of hardwood, special screws, and a combination of both to further fortify the wood.

The best part is that you don’t need to be an experienced DIYer or a professional carpenter or woodworker to make use of these techniques. All you need is the appropriate tools and materials for the job, some patience, and a bit of know-how.

Once you are done with the reinforcing process you can then paint, stain, or varnish the wood as per your preference. Your workpiece will look as good as new and be just as strong.

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