Varnishing wood is one of the best ways to protect and enhance its natural beauty. It's simple to apply, visually appealing and highly durable. Compared to wipe-ons, it has a significantly quicker application while creating a thicker, more protective surface. 

Many woodworkers avoid brushing varnish because they struggle with drips, streaks and brush marks. But that doesn’t have to be the case. With the right approach and the best brush for varnish, you can learn how to apply varnish without brush marks and get a flawless finish every time. In this guide, we'll cover everything from brush selection to mastering varnish application techniques.

Choosing the Best Brush for Varnish

The quality of your brush plays a significant role in the outcome of your project. Not all brushes are created equal, and selecting the right one depends on the type of varnish you’re using.

Natural vs. Synthetic Bristles

• For oil-based varnishes: Use a natural bristle brush, such as a China bristle (hog's hair) brush. Natural bristles are excellent at holding and evenly distributing thicker, oil-based varnishes.
• For water-based varnishes: Choose a synthetic bristle brush, typically made of nylon or polyester. Water-based varnishes cause natural bristles to absorb moisture and splay out, leading to uneven application.

Chisel-edge brushes are ideal for general varnishing, as they provide control and even coverage. A sash brush, on the other hand, with its flagged-tip synthetic bristles, is great for getting into corners and detailed areas and works for both oil-based and water-based varnishes.

Avoid cheap brushes, as they may shed bristles and create streaks. A high-quality brush costs anywhere from $25 to $80 but will last for years with proper care.

Preparing for Varnish Application

A smooth finish starts long before you begin brushing varnish on your workpiece. Proper preparation is key.

Workspace Setup

• Temperature & Humidity: Varnish applies best between 65°F and 80°F with moderate humidity. Extreme temperatures can cause drying issues.
• Lighting: Position a strong, reflective light to illuminate the surface and reveal imperfections as you work.
• Dust Control: Clean your workspace, let dust settle and wear dust-free clothing.

Preparing the Wood Surface

• Sand the wood to 220-grit for a smooth foundation.
• Remove dust using compressed air or a tack cloth.
• Raise the workpiece on triangular sticks or boards with screws for better access and support.

Priming Your Brush

Before starting, prime the brush by dipping it in the appropriate solvent:

• Mineral spirits for oil-based varnish.
• Water for water-based varnish.

This step is crucial because it conditions the bristles, preventing them from absorbing too much varnish too quickly. It also ensures a smoother flow of varnish, reducing the likelihood of streaks or uneven application. Additionally, priming makes cleaning the brush easier after use.

How to Apply Varnish Without Brush Marks

One of the biggest challenges of varnish application is avoiding brush marks. Here’s how to achieve a flawless, glass-like finish.

Step 1: Stir, Don’t Shake

Shaking varnish introduces bubbles that can ruin the final finish. Instead, stir gently to mix it thoroughly.

Step 2: Thin the First Coat

For oil-based varnish, thin the first coat with 10-50% mineral spirits. This improves penetration and makes brushing easier. Some water-based varnishes don’t tolerate thinning, so check the label.

Step 3: Load Your Brush Correctly

• Edges & Corners: Dip just the tip of the brush to prevent excess varnish and drips.
• Broad Surfaces: Load the brush enough for smooth coverage, but avoid overloading to prevent sagging.

Step 4: Apply in Smooth Strokes

• Start at the edges, using a chiseled-edge brush for control.

• Move to the main surface, working in long, continuous strokes.

• Tip off: Lightly drag the tips of the bristles over the wet varnish to smooth out brush marks.

• Avoid back-brushing: Once the varnish starts to set, resist the urge to rework it.
• Wipe away drips: Wrap a clean rag tightly around your finger, and lightly drag it along the underside of the edge to thoroughly wipe away drips. If the faces are already finished, use a very lightly loaded brush to spread out any runs.

Step 5: Let It Dry & Sand Between Coats

• Allow at least 12-24 hours for drying (refer to the product instructions).
• Lightly sand with 320-grit paper before applying the next coat.
• Wipe away dust with a clean, dry cloth before adding another layer.

Fixing Mistakes

Even with careful application, varnish drips and sags can happen. Here’s how to fix them:

• For dried drips: Use a sharp chisel or razor blade to carefully shave off excess varnish.
• For sags: Gently sand the area with 320-grit paper, being careful not to sand through the finish.

Applying Additional Coats for Durability

For the best protection and appearance, apply at least two to three coats of varnish:

• First coat: Thinned varnish for better adhesion.
• Second coat: Full-strength varnish, applied smoothly.
• Final coat: Ensures durability and a professional finish.

Each coat should be sanded lightly and wiped clean before the next application.

Rubbing Out the Finish for a Perfect Sheen

After the final coat has fully cured (a few days to a week):

• Wet-sand with 400-grit wet/dry sandpaper, using mineral spirits or water. 
• Buff with 0000 steel wool for a silky-smooth finish.

• Apply a thin layer of wax for added protection and sheen.

You’re Ready to Begin

Now that you can identify the best varnish brush, know how to prepare your workspace and understand the application techniques, you can master how to apply varnish without brush marks. Your newfound skill will have you producing a beautiful, durable finish every time. 

Content for this article is updated from the original post by Paul Anthony