How to Harden Wood for Painting or Staining?

some methods to harden wood

Wood that can be protected will last for many years.

While wood is still 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.

By hardening the wood, you can keep it close to its original condition for many years.

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

Methods to Harden Wood for Painting or Staining

There are a few methods to harden wood for painting :

1- Polycryl Wood Fortifier

The policy is a wood fortifier, an adhesive that forms a strong chemical bond with the wood surface.

It’s also inexpensive, readily available, and can be easily used simply by reading the instructions. You will need the following items, which begin with the Polycryl.

1- Old or Disposable Paintbrush

2- Gloves

3- Water & Bowl

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. Be sure the wood is fully dry before taking the next step.

Prepare: Dilute the Polycryl in a bowl of water as per the label’s instructions. You’ll need to pour the Polycryl into the water bowl and stir until it forms a thick liquid.

Apply: Apply the Polycryl across the surface of the wood in generous portions. Spread it evenly with the paintbrush.

You do not have to highlight weaker areas; simply cover the entire surface as evenly as possible. You’ll likely have to dispose of the paintbrush once you have applied the Polycryl.

Dry & Check: It normally takes about five hours for the Polycryl to dry fully, but you will need to check with the manufacturer’s label.

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: You will need to use a wood lacquer or varnish to protect the Polycryl.

Either lacquer or varnish should protect against both water and the UV rays of the sun.

The finish will provide an extra layer that keeps the wood hardened for a long time.

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, you will need to purchase the epoxy resin and have the following.

1- Disposable Applicator or Bristle Brush

2- Safety Mask & Gauntlets

3- Putty Knife

4- Water

You will need to set up in a well-ventilated area, preferably outside if you can. 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. Use the putty knife to scrape out all the loose wood fibers from the crevices.

Otherwise, any remaining loose fibers will prevent proper bonding with the epoxy resin.

Mix & Apply: Many epoxy products consist of two separate materials, the epoxy, and the hardener.

While some epoxies can be mixed with water, you will need to follow the formulation as part of the manufacturer’s label.

Pour the mixture onto your wood surface and use a paintbrush to spread it evenly. Use the paintbrush to spread the mixture, or you can use the putty knife.

Drill: If the wood is either too thick or soft to get the results you want from the epoxy, drill a hole in the middle of the wood and add the epoxy inside.

This will harden the wood to an even greater degree as the epoxy spreads into the wood fibers.

Dry & Reapply: You will need to let the mixture dry for about three to four hours, although there should be drying times listed in the instructions.

The smaller the surface, the faster the drying time.

Once dry, reapply with more epoxy layers. 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

This is a simple, effective chemical treatment for wood that does harden it considerably, particularly wood that has experienced rot.

If you have old wood, you can make it tougher using this product. What you will need starts with the wood hardener and includes the following.

1- Soap & Water

2- Putty or Carving Knife

3- Gloves and Face Mask

4- Pressure Sprayer or Paint Brush

Ensure to work in a well-ventilated area.

Prep the Wood: Use the carving or putty knife to scrape away the loose debris, then soap and water to clean out the particles from the decayed part of the wood. Let it dry before you add the hardener.

Prep & Apply the Wood Hardener: Stir or shake the hardener that normally comes in a can or bottle.

Once ready, use an old paintbrush or pressure sprayer to apply the hardener to the surface.

Please make sure the surface is saturated before you let it dry.

Dry & Reapply: It normally takes an hour to two hours 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.

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

process to harden wood for painting

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, but the process itself is quite sound.

The heat from the fire removes the excess moisture, which in turn tightens the wood fibers.

You have to be extra careful to stop not only burning the wood but burning yourself in the process.

You should have some water or a fire extinguisher nearby just in case the worst should occur. This method tends to only work for small pieces of wood.

You will need the proper protection, which includes safety gloves and goggles. You will also need a source of fire which can be charcoal or wood. Plus, a way to ignite it.

Prepare: You will need a fire pit to provide the heat. If you do not have one, dig a firepit about six inches deep and two feet in diameter.

Surround the firepit 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 the heat that you desire.

The flame should be a half-foot in height with a blue center.

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. Check frequently to ensure that the wood is not being burned.

When the wood appears dull and feels tougher, then the moisture has been removed. If you are not satisfied with it, then reapply the heat.

Once done, let the wood cool for about five minutes, and it will be ready.

5- Infusion

Acrylic resin can be infused into the wood to harden it. While the resin itself is much safer to use compared to other materials, the downside is that the method of infusion can be difficult.

You will need the acrylic resin and the following.

1- Vacuum Pump & Chamber

2- Shop Oven

3- Gloves, Goggles, and Face Mask

4- Aluminum Foil

Dry: Use the oven to dry the wood by baking it at 250 degrees F for up to 8 hours, according to its size.

Cool & Place in Vacuum: Let the wood cool and place it in the vacuum chamber. Be sure the wood is properly spaced.

Add Resin: Add the resin and allow the process to last long enough for it to be fully absorbed into the wood.

This may take upwards of two hours, depending on the size of the wood. You can tell once all the air bubbles have ceased forming on the wood.

Sit & Bake: Remove the wood from the vacuum chamber and let it sit for a few minutes.

Once it has sat, 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 the wood from the oven and let it cool to room temperature.

6- Natural Oils

This is one of the simplest methods, but it also takes the longest. Linseed or Tung oil works quite well in hardening softwoods.

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 and create a hard polymer that will form a barrier to moisture.

This will also harden the wood considerably.

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