How To Use Wood Filler

| Last modified on January 27th, 2022

Many people who are hobbyists and DIYers find themselves needing to fill some gaps or holes in their wood project. If you’re looking for a versatile filler that can be used for both interior and exterior projects, consider using a wood filler. 

How To Use Wood Filler

Wood is porous, so it absorbs moisture easily, which will cause the wood to rot quickly if not sealed with a water-resistant sealer. To use wood filler, you need to mix it first, then apply it to the wood with a putty knife, sand the surface and finally finish the wood. This article explains in detail how to properly use wood filler.

What Is Wood Filler?

Wood filler is used for repairing wood by filling the gaps between wood chunks or holes. It can be applied directly on the surface of your project, without sanding or first receiving pre-treatment.

Deciding on Wood Fillers - Fine Homebuilding

In addition, the filler can be easily mixed, made out of different materials such as epoxy, acrylic, and polyurethane, amongst other materials that are available at your local hardware store.

How To Use Wood Filler: Step-By-Step Guide

Wood filler is easy to use, but it requires some extra preparation steps before applying it to your project. You first have to mix the filler before applying it, and the application cannot be made in a rush. Also, if you don’t follow the instructions correctly, you may end up with a lumpy or uneven surface. Here’s how to use wood filler.

Prepare The Surface

Before applying the wood filler, you need to prepare the surface properly for it. Sanding is required because it will ensure you have a smooth and even surface on which you can apply the primer and wood filler later on. It takes time, but sanding will prevent your project from having unsightly marks once dried.

Mix The Wood Filler

Following the directions from the package, mix the wood filler. It is a two-stage process; if you are using an epoxy filler, you need to combine equal parts of resin and hardener. The mixing will produce heat, so keep mixing until it cools down and forms a smooth surface.

Apply The Filler

Using a putty knife or spatula, apply the filler equally on both sides of the project. Be gentle while applying it because too much pressure will cause lumps or uneven surfaces, making sanding difficult later on.

Sand The Wood Filler

For best results, sand the filler. Again, fine-grit sandpaper works best for this and if you’re using coarse-grit sandpaper, put it in a piece of cloth to prevent your fingers from getting scratched.

Wipe The Surface With A Tack Cloth

You can wipe the surface with a tack cloth to remove dust particles and loose filler particles that may have fallen off while applying it.

Finish The Wood

Seal the surface with an appropriate finish to protect it from moisture. You can apply wax or polyurethane depending on the type of finish you’re using for the project.

Water-Based Vs. Petroleum-based Wood Fillers

If you are wondering what wood fillers are and which ones to choose for your next or current project, here is a guide that provides a comprehensive explanation of the differences and offers a few pro tips.

A water-based wood filler is meant to be less toxic to people and the environment than petroleum-based fillers. A water-based filler usually consists of an adhesive agent mixed with sand or crushed granules of glass fiber or walnut shells. 

The soil retarding properties are much better with these types of fillers as well – they will not swell up in areas where they come into contact with the earth, helping create a strong bond between the two surfaces being joined together. Water-based fillers will also not stick to things other than the materials they are intended for.

Petroleum-based fillers are more likely to swell up and can be a problem when you’re trying to create a strong bond between two surfaces. In addition, petroleum products tend not to stick well or at all to surfaces that aren’t used for working with petroleum. 

The unfiltered burns of petroleum will leave harmful chemicals (such as benzene) behind, which can cause skin irritation and breathing problems. If left in your area over time, this can cause health problems. For these reasons, many people choose water-based fillers over petroleum-based ones and environmental concerns.


How Do You Apply Wood Filler?

The best way to apply wood filler is with a putty knife. First, you knead the material until it feels like dough and then rolls it on the surface of your chosen wood.
There are many variations on just how to apply wood filler, but the most common methods involve either using a putty knife or some variation (e.g., a sponge roller). And while there are lots of different variations, one thing that most people would agree on is that you should always try and blend in the filler as much as you can within about 12-24 hours after application- while waiting for the glue to dry properly.

Do You Use Wood Filler Before Or After Sanding?

Wood filler is a topical application that can be applied after the surface has been scraped or ground to remove any high spots. Sometimes, it is possible to get away with only using wood filler without having to sand, but when there are deep gouges or scratches on the surface of the wood, sanding will almost always be required afterward.

How Long Should Wood Filler Dry Before Sanding?

To make the best use of your time, you should wait for your wood filler to be dry within 3-4 hours. If you choose to sand before it has completely dried, the wood filler will be removed in some areas and won’t provide the desired effect. It will also weaken the bond between each layer, leaving you with a soft finish on top of a smooth substrate.

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