Does Wood Filler Harden? + Top Hardeners and Alternatives

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Even for those of us who’ve spent years mastering the art of woodworking, it’s not uncommon to discover exposed joints or nail holes in our final creations. Thankfully, addressing these imperfections is neither complex nor time-consuming when you have wood fillers at your disposal.

Now, if you’re pondering whether wood filler hardens enough to seal cracks or gaps effectively, you’re in the right place. In this guide, I will share my knowledge to ensure you have all the information you need.

Is It Possible To Harden Wood Filler Without a Hardener?

Without a hardener, wood fillers cannot possibly harden. By shielding the wooden surface from external factors like temperature, moisture, and humidity, the wood hardener assists the wood filler in strengthening the integrity of damaged wood. 

However, even without a hardener, ambient oxygen can help the wood filler become more durable. The process can take two to three years to complete and the wood filler won’t dry even after it runs out, instead, it merely settles.

Wood Hardeners That Harden Wood Fillers Fast

Usually, wood filler hardens to a consistency that can be sanded. You should let the wood filler take at least 30 to 60 minutes to harden if you want outstanding results.

putting wood hardener

Here, we’ve included a list of some of the top wood hardeners that work well with wood filler to efficiently patch up wood cracks.

Minwax High-Performance Wood Hardener

Minwax, one of the most reputable companies on the market, developed a superior, high-performance wood hardener that functions in concert with wood filler. It quickly and thoroughly seeps into the wood because of its thin and watery character.

Bondo Rotted Wood Restorer

Bondo manufactures top-notch wood hardeners in addition to items to mend rusted cars. It provides a high degree of convenience, quality, and water resistance, positioning the brand as a premium choice.

LiquidWood Kit

LiquidWood is another wood hardener that works well with wood filler. It is essentially an absorbent epoxy that is graded for structural repairs to bring back the strength of any piece of wood.

The following list of wood hardeners, on the other hand, does not work with the majority of wood fillers.

J-B Weld Original Liquid Hardener

This wood hardener works effectively without requiring the addition of wood filler. Its appearance is milky and watery, which facilitates easy and quick absorption into deteriorated wood.

Additionally, the rapid absorption of the hardener ensures efficient and reliable results for your wood restoration projects.

PC Petrifier Wood Hardener

PC Petrifier Wood Hardener can be used as an outdoor primer in addition to its function as a wood hardener. It has a thick consistency, which makes it much simpler to brush over hard surfaces and somewhat less absorbent.

PC Petrifier Wood Hardener​

Typical Duration For Wood Filler To Harden

The typical time it takes for the wood filler to harden is between 30 and 60 minutes. However, some wood filler does harden quickly based on their type, brand, and base.

An excellent reminder for all woodworkers, especially beginners, is to add wood filler to damaged wood quickly. This prevents it from hardening before you finish applying layers, allowing you to spend more time sanding, painting, or refinishing your wood.

After examining several wood fillers for workability, quality, and adaptability, here are the top 10 wood fillers available in the market today. 

Wood Filler Product

Drying Time

Rust-Oleum Varathane Fill Stick for Wood Repair

10 minutes

FamoWood Wood Filler

15 minutes

Gork’s Goodfilla Water-Based Wood & Grain Filler

15 minutes

3M Bondo Wood Filler

30 minutes

Aqua Coat Grain Filler

1 to 2 hours

DAP Plastic Wood All-Purpose Wood Filler

2 hours

Minwax Color-Matched Wood Filler

2 to 6 hours

Elmer’s Carpenter’s Stainable Wood Filler

up to 8 hours

Elmer’s Carpenter’s Interior Wood Filler 

12 to 24 hours

Coconix Floor and Furniture Repair Kit

up to 24 hours

Recommended Drying Time For Wood Fillers Before Painting And Sanding

The wood filler typically needs 2 to 6 hours to dry completely before you can sand and paint the wood. The kind of wood filler, and the size, depth, and temperature of the cracks, holes, and grooves are still important considerations.

drying wood hardener

Even though the best wood fillers dry in a matter of hours, it’s advisable waiting at least 24 hours before sanding and painting. Also, to achieve the best results, be sure to take into account the manufacturer’s specified estimated drying time. 

However, wood fillers tend to dry so hard that they are difficult to sand. For a more realistic effect, experts recommend using an oscillating sander and sanding the filled area in the same pattern as the wood grain.

How To Make Wood Filler Dry Quickly

As for many woodworkers, the shorter it takes the wood filler to dry and harden, the better. Not only does it complete their project faster but also gives them more time to do other tasks.

Applying wood filler in warm weather is a terrific suggestion from professionals for getting it to dry fast. Summer is the best season to undertake your woodworking projects since they dry quickly.

Still, the drying time of wood fillers is one of the major errors made by woodworkers, which they either underestimate or overestimate. 

There are steps you need to do to speed up the drying process of the wood filler in addition to according to the manufacturer’s guidelines for drying time. Here, we’ve provided 5 simple methods so you may select which wood filler does harden and dry most quickly.

putting wood filler

Step #1: Clean the area

Cleaning the area of the wood you’ll be working on is the first and most crucial step you need to take. To make the wood clear and clean, remove any dust, stains, or paint and scrape away any splinters.

Once you’ve meticulously scrubbed and scraped the entire wooden piece, place it in a warm and dry spot, preferably under sunlight. This setting facilitates quicker drying, allowing you to transition to the subsequent step in your process smoothly.

Step #2: Combine Wood Filler And Hardener

The next step is to get the wood filler ready. On a piece of wood board, blend wood filler and hardener using a putty knife. The ingredients should be well blended after kneading them back and forth. 

Also, it helps when you warm the wood filler first before the application method. Do this using a thermostat or heat gun to shorten the time it will take for the wood filler to dry and harden.

Step #3: Apply And Layer Wood Filler

After combining the wood filler and hardener, take a sizable portion of the mixture and spread it over the wood’s damaged area. To ensure that there is ample room for moisture to escape and speed up drying, apply thin coats of wood filler layer by layer.

mixing wood hardener and wood filler

Applying a little coating of wood filler at a time and waiting for it to cure and dry before adding further coats are key.

Step #4: Keep The Wood Warm

After applying many coats of wood filler to the board, the drying process must be completed by warming the wood for around 15 to 30 minutes. To hasten the wood filler’s hardening and drying, it’s advisable to expose the wood to sunshine. 

You may also use a hair dryer or a fan to blow air into your woodworking area. This increases air circulation while decreasing humidity and the drying and hardening time of the wood filler.

Step #5: Sanding

Sanding can then be done once the wood has completely cured. The wood may now be stained or painted to give it a polished, tidy, and smooth appearance. Wear a dust mask while sanding the wood for your protection because wood may be damaging to your respiration.

Once you’ve finished sanding, dry the wood in the sun or with a hairdryer before applying a stain or paint to complete your woodworking projects.

sanding wood filler

Reasons Why Wood Fillers Tend to Crack

Wood fillers frequently break because they have not yet fully dried and set. Additionally, wood fillers may fracture as a result of temperature fluctuations [1] in the area when they contract or expand. 

It’s recommended to maintain the wood in a warm, dry environment and wait until the wood surface is dried before applying another coat or moving on to the next phase.

Methods To Fix Cracked Wood FIllers

It’s crucial to know how deep or large the region you will be working on is and the quality of the wood is finished before you fill in those fractures. With this, you can choose where to start and how much wood filler to use.

Thankfully, there are two ways to repair cracked wood filler without further harming the wood.

  1. The first technique involves totally removing the old wood fillings and beginning anew. After that, apply a thin coating of wood filler in the proper quantity to the crack and allow it to cure.
  2. The second involves applying varnish to the wood fillers used to repair cracks. It is a simple and effective way to keep the fracture in place and conceal it. 

Wood Hardener Alternatives

There are several alternatives to the conventional chemical-based wood hardeners that you might employ in your next woodworking projects. These substitutes for wood hardeners are durable, dependable, and, most importantly, successful in hardening wood.

acrylic resin

The following are some of the greatest alternatives to wood hardeners.

Acrylic Resin

Try acrylic resin if you are sensitive to wood hardeners made of chemicals. It is water-based, contains tough polymer emulsions, and is effective on wood.

In addition, acrylic resin is a popular choice among woodworkers because of its quick-drying capabilities, ease of production, powerful protection, and attractive decorating.

Epoxy Resin

Despite being chemically based, epoxy resin is a fantastic substitute for wood hardeners since it strengthens fragile wood. The strength of the wood fiber will be more effectively embodied if the acrylic resin is poured into the drill hole.

Epoxy resin is waterproof, making it a great wood sealer for preserving the natural look of furniture, floors, and tabletops while preventing cracking, peeling, and rotting. But is epoxy resin food-safe? Let’s find out next. 

Natural Oils

To provide a barrier against entering moisture or water and harden and tighten your wood, utilize natural oils like linseed or Tung. Although it could be a simple and natural procedure, the curing process might take some time.

natural oil

What’s nice about utilizing natural oils is that they act as a protective barrier that soaks in while leaving the natural texture and color of the wood alone.

Pentacryl Hardener

Although using a pentacryl hardener may cost more, after the wood has dried, it cannot be easily broken. All that is required is to place a plastic bag over the wood, let the hardener soak, and then allow the wood to dry. 

Furthermore, when exposed to varying degrees of temperature and humidity, pentacryl does not discolor, degrade, or oxidize the wood.

Polycryl Wood Fortifier

Lastly, a Polycryl wood fortifier is a wood hardener alternative that can harden the surface of the wood yet does not penetrate deeply into the wood fiber. 

However, a generous amount of this wood hardener alternative can close the wood pores, provide a shiny surface, and prevent wood damage for a long time.


Does Wood Filler Get Hard Like The Wood?

Indeed, once wood filler has fully cured and dried, it attains a hardness comparable to wood itself. While numerous wood fillers on the market promise to dry and solidify within mere minutes, allow a window of 30 to 60 minutes to ensure optimal results. 

Given its capacity to harden like wood, wood filler proves to be an outstanding option for repairing damage and restoring the integrity of your wooden items or structures.

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Wood fillers offer a wealth of knowledge yet to be uncovered, and in this post, let me demystify the notion, confirming that wood filler indeed hardens. 

Moreover, integrating top-tier wood fillers and hardeners, paired with the application of proper techniques, paves the way for more effective and gratifying experiences in your future woodworking ventures!

Robert Johnson is a passionate furniture maker & carpenter, sought after for his knowledge on the craft.
You've probably seen his down-to-earth wisdom in USA Today, Bobvila, Family Handyman, and The Spruce, where he has shared commentary and guidance on various woodworking topics.

Robert is the brain behind Sawinery, where he aims to share tips, tricks, and a passion for all things carpentry.
Robert Johnson

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