do you have to use hardener with wood filler?

Wood filler is a material used to fill holes and cracks in wood. It comes in either a dry powder that you mix with water or as a pre-mixed putty. In order for the wood filler to be set properly, you need to add an additional component called hardener, which is typically sold separately from the wood filler itself.

Even if your wood filler does not come pre-mixed with hardener or has already started setting before adding it, there are ways of getting around this issue so that your project stays on schedule!

What happens if you don’t add hardener to wood filler?

The main difference between using a hardener and not using it is that the filler will not harden. It will also not be as strong as it could be, it will be more difficult to sand and paint, and you’ll have to work with a less-than-ideal product.

However, if you don’t use treated wood filler in the first place (for instance, if your project calls for unpainted wood), then there’s no sense in adding something else just because someone told you to do so.

Do I need wood hardener?

Wood hardener is a liquid added to wood filler to make it stronger. You can add wood hardener when you mix the wood filler or use it as an alternative to using a stain on your wood surface.

The amount of hardener needed depends on the size of your project and whether you are using a brush or roller.

The manufacturer’s instructions will give you specific measurements for different applications, but in general, if you are filling large holes in your wall with this product then less is more; if you want your walls to look like they have been professionally spackled then more might be better (but remember that this will make them darker).

If necessary, repeat this process until all imperfections have been filled and sanded flat until smooth enough for painting/staining depending on what type of surface treatment was done before applying any kind of filler material makes sense.

Can you put wood hardener on wood filler?

You can put wood hardener on wood filler, but you will have to sand it down to the area where you applied the wood hardener. It’s not very thick and won’t take up much space, so it shouldn’t be a problem.

Will fillers be set without a hardener?

Yes, fillers will be set without a hardener. The exact time it takes to set depends on the brand of filler and your current conditions (temperature and humidity).

If you want to speed up the process, use a blow dryer or heating pad to warm up the surface of your object before applying the filler. This helps it cure more quickly and gives you better results.

Why does my wood filler keep cracking?

Wood filler cracking is often caused by too much moisture in the wood. Water expands when it freezes, so if you’re working in a very cold environment and your wood filler doesn’t get enough time to harden completely before the temperature drops, this could cause cracking.

To remedy this issue, try applying another coat of hardener or letting it sit longer before using.

If you don’t have enough moisture in your wood filler, then you might experience some cracking as well. Add more water to thin out or stir until smooth before applying again if needed to fix this problem.

In addition to these issues with moisture content, another common reason for cracked wood filler is not adding enough hardener (or not using an appropriate kind).

If you think this might be the case for any areas that are cracking consistently after each application of new layers of filler/glue-like substance onto them during repairing jobs around your house — particularly when trying different brands — try changing up which brand/type of glue/filler-like stuff works best with

How long does wood filler take to harden?

It can take anywhere from a couple of hours to 24 hours for wood filler to harden. The amount of time it takes depends on several factors, including humidity and temperature.

If you’re working in an area where the humidity is high or the temperature is low, your wood filler will take longer to harden than if you were working in a dryer climate with higher temperatures.

Why is my wood filler not drying?

  • It can take up to 24 hours for the wood filler to dry.
  • If your wood filler is still wet, it will not hold paint. You may need to wait until it fully dries before you paint over it. You can speed up this process by using a blow dryer and/or a heat gun.

How do you seal wood filler?

After you’ve finished applying and sanding the wood filler, it’s time to seal it. There are two ways you can approach this process: use a brush or use a rag.

  • Use a brush for better coverage
  • Use a rag for less mess
  • Make sure the sealer is dry before sanding
  • Seal the filler before applying a finish

How do you mix wood filler and hardener?

The mixing ratio for wood filler and hardener can vary depending on the brand. Generally, it’s a 1:1 mix—one part hardener to one part wood filler.

Make sure you stir the mixture from time to time so that it doesn’t separate. After you’ve mixed the two together, apply your mixture with a putty knife or paintbrush in even strokes across all areas of damage.

You don’t want to leave any gaps between layers because this will cause the surface to become uneven over time.

You want to make sure you give each layer enough time to dry so as not to interfere with the later application of another coat of mixture or further sanding if necessary.


As you can see, there are some instances where a hardener is not necessary when using wood filler. However, it’s important to note that if you are going to use an oil-based filler then it will need a hardener.

In general, most people find that wood fillers work best with or without hardeners so there isn’t a huge difference between them unless you’re working on a project that needs extra strength or durability like repairing cracks in a wooden floorboard.

Photo of author

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.

Leave a Comment