When working on natural wood, it’s common to find knots, cracks, and gaps on the surface. These imperfections can show up naturally or as a result of general wear and tear.
Though they can add charm to decor, they’re not ideal on furniture that needs to be functional and sturdy. Here’s how to fill in cracks or voids in wood using Durham’s Rock Hard Water Putty, as well as tips to get the best results.
Supplies You’ll Need
- Durham’s Rock Hard Water Putty
- Colorant of choice (mica powder, water-based stain, or paint)
- Craft sticks (for mixing)
- Soft brush (for dusting off sawdust)
- Sandpaper or sander
- Finish (penetrating oil and top coat)
Step 1: Mix Up Durham’s Water Putty With Colorant
Scoop a small amount of Durham’s powder into a clean, disposable container. Use a ratio of 3:1, or 3 parts dry putty powder to 1 part water. Then, gradually add your colorant of choice into the mixture.
I like using mica powder because it’s pigmented and adds a shimmering, pearlescent finish to the wood. Start with about 1 teaspoon and gradually add more until you reach the desired color. A little goes a long way. Mix until you reach a consistency of smooth peanut butter.
If you don’t have mica powder, you can use a water-based wood stain or acrylic paint. Coffee grounds or instant coffee work, too, especially if you want to create that aged wood effect. Just be aware that it can be inconsistent or patchy in tone.
Avoid oil-based paints because they can interfere with the curing process.
Step 2: See if It Matches the Area You’re Trying To Fill Color-Wise
Dab a bit of the dry putty-colorant mix on a similar piece of scrap wood or an inconspicuous area. Let it dry and compare it to the original wood.
If the color appears too light, add a darker pigment. If it’s too dark, lighten the mix with more putty. Repeat the test as needed until it matches the color of the area you’re looking to fill.
The putty will lighten as it dries, so you’ll want to make the color a bit darker than the wood you’re filling.
Step 3: Adjust the Consistency of the Putty And Colorant Mix, If Necessary
The putty mixture should easily spread, adhere to the wood surface, and press firmly into the crack or void. It should be malleable enough to push into narrow gaps but stiff enough not to sag or slump out of deeper voids.
If the putty is too thick or dry, add small amounts of water until you reach a consistency of peanut butter. If it’s too runny or wet, add more dry Durham’s powder a little at a time.
Make sure the mixture is smooth and doesn’t have any lumps.
Step 4: Spread the Putty Over the Cracks
Now comes the fun part—spreading the putty over the cracks!
Using a craft stick, scoop a bit of the putty mixture and press it firmly into the cracks or voids. You’ll want to slightly overfill the area to account for shrinkage as it dries. Scrape the excess off with a plastic scraper or old credit card.
Step 5: Let the Putty Fully Dry
Durham’s Putty dries quickly, usually within 40 minutes. But for best results, let it dry overnight. You want the putty to be fully hard before sanding and finishing.
Step 6: Sand the Surface to Remove Excess Putty
Once dry, sand the area with medium-grit sandpaper to remove old rough spots and old finishes, then with fine-grit sandpaper for a smoother surface. You can also use a sander to speed up the process.
Sand in the direction of the wood grain, not against it. Use even pressure and don’t linger too long in one area to prevent scratching the surface.
At this point, the putty should blend in with the wood surface. If you tinted your putty well, the filled areas will visually fade into the wood.
Step 7: Apply a Penetrating Oil
Using a large, soft brush, sweep the dust off your wooden surface. Then, use a lightly damp microfiber cloth to wipe away any remaining fine dust particles. The surface should be completely clean and smooth before applying the finish.
With the surface clean and dry, you can now apply a finish to protect the wood. You can use whatever finish you have available, whether that be a stain, oil, or varnish.
What I usually do is apply a penetrating oil first, then brush on a top coat after.
Use a cloth or brush to apply the penetrating oil. Saturate the wood so the oil penetrates deeply. Let it soak for about 15 to 30 minutes, then wipe off any excess oil with a clean, dry cloth so you won’t get a sticky residue.
Step 8: Seal With Top Coat
Once the penetrating oil has fully cured, apply a top coat to seal and protect the wood surface. You can use either an oil-based top coat or a water-based finish like varnish, polyurethane, or lacquer.
Oil-based finishes add a warm, amber tone to the wood. And though they take longer to dry than water-based finishes (up to 24 hours), they create a hard, glossy finish that resists scruffs and scratches.
Meanwhile, water-based finishes preserve the wood’s natural color. It doesn’t yellow over time, which is preferable if you want a clear finish that doesn’t change the wood’s original tone.
Water-based finishes dry within 2 to 8 hours and tend to be slightly less durable than oil-based finishes. What I like about it, though, is that they can be cleaned up with soap and water, making them much easier to clean than oil-based finishes, which require special solvents.
The application method is the same, regardless of the finish you use. Apply thin, even coats with the grain using a high-quality brush, and allow each coat to fully dry between applications. Apply 2 to 3 coats for best protection.
And there you have it—you’ve successfully filled in the cracks or voids in your wood project! The process is pretty straightforward; the only ‘difficult’ part of the project is waiting for the putty and finish to dry!
Tips for Filling Cracks or Voids in Wood
Here are some useful tips to keep in mind when filling cracks or voids in wood:
- If you’re working with decorative woodwork, tape off the area around the crack to prevent the putty or colorant from staining the surrounding wood grain.
- For cracks or knot holes that go all the way through the wood, tape the other end with painter’s tape to prevent the putty from oozing out as it dries.
- When filling deep cracks or holes, apply the putty in layers and let each one dry before adding the next. This technique prevents cracking, sagging, or hollow spots once dried.
- If the wood you’re working on has multiple holes or cracks, write down the exact recipe of your putty + colorant base (e.g., 3:1 putty, ½ teaspoon burnt amber, 1 drop of black). This way, you can recreate the exact shade if you run out or need to patch additional areas. It’s also good for future touch-ups if more cracks appear or a repair is needed.
FAQs
Can I make my own DIY filler at home?
Yes, you can make your own filler with sawdust and glue.
Sand an inconspicuous area of the wood and mix the collected sawdust with carpenter’s glue. Then, pack that mixture into the cracks or holes.
Note that this homemade filler won’t be as hard, stable, or sandable as Durham’s Water Putty. It tends to shrink more as it dries, and can sometimes appear glossier or darker than the surrounding wood when finished.
This DIY filler is best for small gaps or nail holes, not for structural voids or deep cracks.
Why use Durham’s Rock Hard Water Putty over other water putties?
Durham’s Rock Hard Water Putty has long since been a favorite for DIYers and woodworkers because:
- It doesn’t shrink as it cures
- It hardens into a rock-hard, scratch-resistant surface that can be sawed, sanded, polished, or colored
- It comes as a dry powder that you can mix with water, allowing you to prepare only the amount you need
Other water putties don’t dry as hard as Durham’s, have a strong chemical odor, or have no powder form. Durham’s is affordable, too, costing around $10 per 1-pound can.
Can I stain over Durham’s Water Putty?
Durham’s Water Putty doesn’t stain after it has cured. If you want to add color, mix the stain into the mixture while wet.
Can I drill or screw into the putty?
Yes, you can drill and screw into Durham’s Rock Hard Water putty.
You can insert the screw into the putty while it’s still wet then allow it to dry completely, or wait until the putty is fully cured before drilling a hole into it.
If you do the latter, make sure to pre-drill a hole in the putty to prevent it from cracking.
