April 15, 2023

Can you use wood glue to fill holes?

Wood glue is a fast-drying adhesive that can bond two pieces of wood together. It is for filling in holes and cracks in the wood. The surface remains uniform as it dries clear and is practically invisible. Use the glue and toothpicks method if the wood has a deep hole.

Some liquid wood glues are too runny, hence the need for more like putty, such as epoxy. If your wood glue is not thick enough, mix sawdust with glue and make your filler.

Whatever wood glue you need is available at any hardware store around. You can find wood glue in the stores where you buy wood filler. Wood glue shrinks as it dries. If the hole you filled is not full once the wood glue or wood filler has dried, add more to the top.

Allow your project twenty-four hours for the wood glue to cure. That way, the wood glue is not disturbed upon moving your project or removing a clamp. Wood glue dries before it cures. Wood glue is a powerful adhesive for strong connections from edge grain to edge grain. Some types of wood glue are waterproof and perfect for outdoor use.

Sand wood glue after it has dried. Sanding wood is an essential part of woodworking, which requires 150-grit sandpaper. Amongst the glue types are epoxy and polyurethane. This article seeks to unpack the types of wood glue and how it is applied for a perfect finish. 

Types of Wood Glue

Epoxy

Epoxy is the best for filling gaps. When it dries, it thickens and becomes more like putty than liquid. Use a 1:1 ratio of wood glue to sawdust. Epoxy is a polymer with a high tensile strength ranging from at least 5,000 PSI to upwards of 10,000 PSI. Most epoxy resins come in two parts and must be mixed to activate.

Epoxy is waterproof, and the cure times vary. Epoxies such as JB WoodWeld Epoxy are set in 6 minutes and cured in one to three hours, whereas other epoxies can take days to cure (Repairing Products.co.uk). Epoxies fill in cracks and voids. It comes in handy when you have a misaligned joint. Mix sawdust and epoxy and rub them into any gaps, blending well into the finished wood. However, epoxies are not affordable and do not work well with acidic woods or when a wood block has remaining moisture.

Polyurethane 

Polyurethane is a synthetic plastic resin that works better in humid conditions since it is motivated by moisture. It is water-resistant and waterproof. It is versatile in many other applications. Polyurethane glue shines in unique scenarios where PVA glues fall flat. It can bond end grain to end grain well. It is ideal for oily woods. 

Water-based wood glues do not perform well bonding oily woods, whereas polyurethane glues excel in this area. Polyurethane glues don’t swell woods as water-based glues can. Polyurethane glues offer long assembly times of up to 30 minutes, with a short clamping time. It performs better for finished wood. However,  polyurethane glue is more toxic than other types of wood glue and is not affordable. They also are more difficult to clean up. 

Polyvinyl acetate glue

Polyvinyl acetate is the most common type of wood glue. It is usually yellow or white. It is more affordable, versatile for indoor and outdoor projects, easy to clean up, and strong. When dried, PVA glue creates a stronger bond than the wood itself. PVA glue is also water-based and water-soluble, which makes for easy cleanup. Apply the glue to your project with a wood glue brush, finger, or a wood glue dispenser, and then wipe with a wet rag to remove any residue (Ptreeusa.com).

Assembly times for PVA glues range from 10-15 minutes, but for some, as long as 20 to 30 minutes. It takes 24 hours to cure and is applied at temperatures of at least 50 to 55 degrees Fahrenheit. Their bonding strength ranges from 3,600 to 4,000 PSI. Some PVA glues are food safe and rated by the FDA for indirect food contact, meaning they can be for cutting boards.

Preparing the Surface

Steps needed to properly prepare the surface of the wood before filling the hole with glue

  1. Gather your tools and materials for the project. Do not forget sandpaper, a shop vacuum, tack cloth, wood glue, a wood stain preconditioner, and a putty knife. 
  2. Sand and clean the wood surface. Prepare the damaged surface by removing any loose wood chunks or flaking paint. Sand any rough edges in. Clear away all dust and debris using a shop vac or moistened tack cloth. If you use a damp cloth, wait for the area to dry before you proceed to the next step.
  3. Use a preconditioner on the damaged area to prevent color discoloration since the surface of the wood in contact with the wood filler is susceptible to absorbing the stain or color of the wood filler. Protect the exposed parts of the wood by applying a wood stain preconditioner to seal the damaged area and surrounding surface. Let the conditioner fully dry.

Discuss the importance of cleaning, sanding, and conditioning the wood.

Cleaning helps the surface come smooth without pimples. Sanding ensures that all the defects on the wooden surface are eliminated. Sandpaper can easily remove defects, such as cut marks, burns, indentations, stains, scratches, glue spots, and raised grains. Conditioning helps even out the color when working with bare wood. It penetrates and seals the wood to even out the absorption rate. That is how you end up with a uniform stain coat.

Applying the Glue

The process of filling a hole with wood glue, including the tools and equipment needed

  1. Use PVA glue, toothpicks, a hammer, a knife, and fine-grit sandpaper. 
  2. Put together the required number of toothpicks that will fit into the hole tightly. Dip the toothpicks in PVA glue and insert them into the hole. You can partly fill the wood hole with wood glue and then stick the toothpicks into the hole until no void is left.
  3. Hammer the toothpicks into the hole to ensure the fill is compact. Let the glue dry and cure before trimming the extra toothpick length.
  4. Use a hacksaw or clerical knife to cut the toothpick edges from the wood surface.
  5. Use fine-grit sandpaper to sand the area until it is even with the rest of the wood. Clean up the dust and finish the wooden surface.

Tips and tricks for achieving the best results 

  • Use a putty knife.
  • Clamp the wood.
  • Clean the hole as best as you can.
  • Add sawdust from your wood.
  • Let the filler dry completely.

Finishing the Repair

Steps needed to finish the repair once the glue has dried.

  1. Remove excess glue from your workpiece by rubbing sawdust all over the joint. The sawdust will mix with the glue and clamp together, making cleanup a breeze. Avoid using a wet towel or sponge, as moisture causes wood to swell, and too much might deform your work. 
  2. Clean up the extra glue as soon as possible since wood that absorbs glue will stain differently than the rest.
  3. Sand it down to achieve a smooth, even finish so that the wood filler matches the rest of the wooden surface. When wiping the surface, there should not be a clear difference between the wood and the filler.

Different options for sanding and staining the wood to match the surrounding area

Sanding to grit

When using wood stain, sand to the right grit. Sanding wood too coarsely will create a darker appearance since larger pores and a rougher surface in the wood.

Color match samples

Before staining onto the wood, make sure you have the right mix. If you are unsure how the stain turns out, use samples. Grab some similar wood samples and test your stain formula on them. Sand and clean them the same as your workpiece so that they will yield the same results.

Find a wood sample of the same grain and species

Use a sample for comparison to find a more accurate match. The wood’s grain and species can affect how the stain will appear once dry. If you have any excess material in that same grain and species, use that as the sample.

Conclusion

In summary, several types of wood glue are used to fill holes in your wood. They are epoxy, polyurethane, and polyvinyl acetate glue. Polyvinyl acetate glue is the best wood glue because it is less expensive, versatile, easy to clean, and strong. Wood glue can be an effective solution for filling holes in wood. Experiment with different types of glue and techniques to find the best solution for your project.

FAQs

Can I use wood filler instead of wood glue to fill holes?

While wood putty can be used to fill gaps, cracks, or holes in wood, it is important to know that wood putty and wood glue serve different purposes and are not interchangeable in all situations. Wood glue creates a strong and permanent bond between two pieces of wood, while wood filler is designed to fill gaps and imperfections. While wood glue may be necessary for certain repairs, such as joining two pieces of wood together, a wood filler may be better for other repairs, especially if the wood glue is not strong enough to hold the repair. Therefore, whether wood filler or wood glue is, the better choice depends on the type of repair and the condition of the wood. It is recommended to carefully assess the damage and choose the appropriate product for the job to ensure a strong and durable repair.

How long does it take for wood glue to dry?

While some types of wood glue can dry in as little as ten to thirty minutes, the actual drying time depends on several factors. For example, the type of wood glue, the temperature and humidity of the environment, and the amount of glue applied can all affect drying time. Some types of wood glue, such as PVA glue, require a longer drying time than others and may take several hours or even overnight to dry completely. Thicker applied glue can also take longer to dry than thinner glue. Therefore, it is important to consult the manufacturer’s instructions for your wood glue to determine the recommended drying time. It is generally recommended to allow the glue to dry completely before handling the glued object to ensure a strong and permanent bond.

What is the best wood glue for filling holes?

Epoxy can fill holes and cracks in wood, but it is not the best choice. For filling small holes and gaps in the wood, a wood filler or putty designed for this purpose may provide a more seamless result than epoxy. Also, some wood glues have a thicker consistency, making them ideal for filling larger holes and gaps. So, which wood glue is best for filling holes depends on the hole size or gap type. A wood filler or putty is usually recommended for small holes and gaps, while larger holes may require a wood glue with a thicker consistency or an epoxy. It is important to carefully assess the damage and choose the right wood glue or filler.

Can I paint over wood glue after filling a hole?

While it is true that wood glue must dry completely before you paint over a hole or gap, it may not be the best option for this purpose. Wood glue may not be as durable as other options, such as wood filler or putty, which can cause the glue to crack or shrink over time and affect the quality of the paint job. In addition, the texture and consistency of the wood glue may not match that of the surrounding wood, resulting in an uneven or unattractive finish. Therefore, it is generally recommended to use a wood filler or putty specifically designed for this purpose. These products can provide a more durable and seamless result when painting over holes or gaps in the wood.

Can I use wood glue to fill gaps in the wood?

While wood glue can fill gaps in wood, it may not be the best solution for all gaps or damage. While it is true that wood glue dries clear and is invisible in certain situations, it can still be visible on certain types of wood or in certain lighting conditions. Also, using wood glue to fill gaps is not a permanent solution and could fail over time. Therefore, it is important to carefully assess the damage and decide if wood glue is the best solution or if another option, such as wood filler, is more suitable.

David D. Hughes

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