What happens if you use wood filler without a hardener?

Wood filler is a great tool for repairing and restoring your wood projects. It’s easy to use, looks relatively nice, doesn’t cost much, and comes in dozens of colors.

The only downside is that wood filler sometimes has a mind of its own. If you’ve ever tried using wood filler without hardener and then found yourself cursing under your breath as it kept cracking or pulling away from the wood before it dried, don’t worry!

In this article, we’ll talk about what causes this problem in the first place so that you can avoid it in the future!

Can I use wood filler without a hardener?

Yes, you can use wood filler without a hardener.

So what’s the difference between wood filler and wood putty? The main difference is that putties are generally softer than fillers and more malleable.

They’re best suited for filling dents in softer woods like pine, whereas fillers should be used on harder woods like maple and oak.

What is the purpose of non hardening wood filler?

  • Non-hardening wood filler is used to fill small gaps in wood.
  • It is used to fill nail holes in wood.
  • It is used to fill cracks in wood.

Do I need a wood hardener?

You don’t need a wood hardener, but you can use wood filler without it. Wood filler and wood putty are different products, although they’re often used interchangeably and sometimes called by the same name.

While they’ll both do the job of filling in cracks and holes, their properties are quite different: wood putty has more pigment than filler, which makes it darker in color.

Putty also comes in a wider variety of colors than filler does (although there are still fewer choices than paint).

Wood putty is also softer than most types of fillers used for home repairs because it contains mineral oil as a binder agent instead of polyvinyl acetate (PVA) like most other fillers do; this makes it easier to work with by hand but less durable over time because its porous nature allows water to seep into any gaps between grains within the particle size range during rainstorms or even just from humidity alone over time if not properly sealed after application.”

Does wood filler strengthen wood?

Wood filler is not a structural material, and it can’t be used to replace wood. It’s meant only to fill holes and cracks in wood. It won’t add any strength to your project.

Wood filler comes in two different types: one that hardens with age (polymer-based), and one that hardens instantly when you apply heat (epoxy).

The polymer type requires the use of a separate hardener, while the epoxy type already has its own hardening agent built in.

Why does my wood filler keep cracking?

It’s not always easy to pinpoint the exact cause of a problem, and wood filler is no exception. But here are some things to look for:

  • Too much moisture in the wood. If you have a lot of moisture in your project, it can cause the sealer and/or primer on top of your filler to crack. The best way to know if this might be an issue is by checking with other projects you may have done—if they all seem fine, then it’s likely not an issue with your product or materials (but definitely keep an eye out for any new projects).
  • The wood filler was too thick when applied. Wood fillers should be applied very thin so they don’t sag while drying—this can help prevent cracking issues as well as ensure proper adhesion between layers.
  • The wood filler wasn’t dry enough before applying another coat over top (for example, another coat of primer). This will also lead to cracking problems because layers aren’t adhering properly together due to excess moisture in between them.

How do you stop wood filler from cracking?

If you’re trying to use wood filler as an adhesive, it will likely fail. Wood filler is generally used to fill small gaps and holes in wood. It fills the space between two pieces of wood and leaves no trace of a seam once it dries.

Wood hardener is the liquid that makes the glue-like consistency turn into concrete when mixed with water.

The hardener prevents cracking in your project by allowing for extra drying time, allowing the mixture to be properly set up before being exposed to moisture again.

To use a wood hardener:

  • Mix equal parts of hardener and water together until they are well combined; then add them slowly into your mix of glue/wood filler while stirring constantly so that they don’t separate from each other
  • You can also use a wood hardener as glue if you want more strength than just filling small gaps with standard white school glue

How big of a gap can wood filler fill?

So what happens if you use wood filler without a hardener? Well, it depends on how big of a gap you’re trying to fill.

  • You can fill a gap that’s 1/8″ or less with no problem at all. If your gap is larger than this size, go ahead and add some hardener to the mix before filling it!
  • For gaps between 1/4″ and 3/8″, try using two applications of filler without any hardener—that should do it!
  • Gaps between 3/8″ and 1/2″ don’t take too much effort to fix with regular wood filler without any added chemicals. A second application might be needed for bigger gaps though!
  • Larger gaps between 1/2″ and 1″? You’ll probably want to use some sort of special compound made specifically for filling holes that are larger than those mentioned above (and you may also need something like an epoxy).

Should I use wood putty or wood filler?

Understanding the difference between wood putty and wood filler can be a little confusing. While they are both designed to fill gaps and holes in wood, they do so in different ways.

Wood putty is used to fill small cracks and holes in the surface of your project, while wood filler is used for larger gaps or voids.

Wood putty usually comes with an applicator that allows you to apply it into the crevices you want to fill before sanding down with fine grit sandpaper or steel wool.

Wood filler is generally easier than using wood putty but doesn’t always provide as nice of results because it tends to shrink when drying out, leaving visible lines where you applied it on your project


Hopefully, we have answered some of your questions about wood filler and hardener. If you still have some questions, please feel free to leave them below. We’d love to hear from you!

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Martin Flood

Martin Flood has been working in the construction industry for over 20 years as a general contractor with expertise in remodeling projects that are large or small. He has furthered his career by specializing in epoxy resin flooring, providing excellent service to both commercial and residential clients. Martin’s experience enables him to offer professional advice on how to choose the right type of project based on your needs and budget.

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