Water based varnish has become an increasingly popular option for wood finishes in recent years. As consumers and professionals alike look for lower VOC options that are safer and better for the environment, water based varnishes present an appealing choice. But how do they really compare to traditional varnishes in terms of performance and durability? Here we’ll take a look at the pros and cons of water based varnish to help you decide if it’s the right option for your next wood finishing project.
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What is water based varnish?
Water based varnish, also called waterborne varnish, is made with water as the solvent rather than chemicals like mineral spirits. Traditional varnish uses solvents like mineral spirits, alcohol, or lacquer thinner to dissolve the resins and create a liquid coating that dries on the wood. Water based varnishes use water to dissolve the resins, along with some small amounts of co-solvents.
The main resin used in water based varnishes is polyurethane, the same resin used in traditional oil based varnishes. The polyurethane resins are suspended in water rather than chemical solvents. As the water evaporates, the resins cross-link to create a hard, durable finish.
Pros of water based varnish
Here are some of the major advantages of choosing a water based varnish:
Lower VOCs
VOCs (volatile organic compounds) are released as the solvents in varnish dry. High VOC exposure has been linked to health issues and environmental pollution. Water based varnishes contain fewer VOCs and solvents than traditional oil based options. While not completely VOC-free, they provide a lower toxicity solution.
Faster drying time
Since water evaporates more quickly than chemical solvents, water based varnishes dry faster. This means you can apply multiple coats in one day rather than waiting a full day between coats. Faster drying time makes the project go more quickly.
Easier cleanup
Cleanup requires only soap and water, while oil based varnishes need mineral spirits for cleanup. Water cleanup is safer and more environmentally friendly.
Less yellowing
Oil based varnish yellows over time, giving wood a warm amber tone. While this is desirable on some furniture styles, it may not be ideal for all wood projects. Water based varnishes resist yellowing better over time.
Easier application
Water based varnishes go on easily without dragging or stickiness like oil-based varieties. They have a smooth, easy learning curve for beginners.
Safer for users
The lack of strong solvent fumes makes water based varnishes safer to use, especially indoors. There’s less risk of respiratory irritation during application. Once dried, water based finishes are non-toxic unlike some solvent-based options.
Cons of water based varnish
While water based varnishes have some clear advantages, they also come with a few downsides:
Not as durable
Oil based varnishes generally create a harder, more durable finish. They wear better over time and protect wood surfaces longer than water based options. For frequently used surfaces like tables or flooring, an oil-based varnish may be a better choice.
Longer curing time
Though they dry quickly at first, it takes water based varnishes a week or longer to fully cure. The finish may remain softer, less scratch resistant, and more vulnerable to damage until fully cured. Oil based varnishes cure harder in just a few days.
Not for use on bare wood
Bare wood needs to be sealed before applying water based varnish. The water raises the wood grain creating roughness. A layer of sanding sealer or oil based varnish should be used first.
Prone to blushing
If temperatures are low or humidity is high during application, water based varnishes can turn cloudy or opaque. This blushing effect ruins the finish, so weather conditions need to be ideal.
Shorter shelf life after opening
Once opened, water based varnish only lasts about a year before going bad. Oil based varieties can last 3-5 years or more after opening. Proper storage extends the shelf life somewhat.
Best uses for water based varnish
Though not right for every project, water based varnishes perform excellently in certain applications:
– Indoor furniture – Dries fast without fumes making it ideal for indoor wood furniture. Provides good scratch resistance once cured.
– Children’s toys – The non-toxic water based finish is safer for kids’ items.
– Kitchen cabinets – With good moisture and heat resistance, water based varnish holds up well on kitchen cabinets. Easier cleanup is a bonus.
– Doors and trim – Quick dry time facilitates application on doors, baseboards, and moldings.
– Sealers under epoxy – Water based varnishes make excellent sealers under epoxy to avoid blushing issues.
– Bartops and vanities – Good chemical resistance suits water based varnish for bathroom vanity tops and bar surfaces.
Comparison of water based and oil based varnish properties
| Property | Water based varnish | Oil based varnish |
|---|---|---|
| VOC content | Low | High |
| Drying time | Fast, under 2 hours | Slow, over 8 hours |
| Curing time | 7 days or more | 3-5 days |
| Durability | Moderate | Excellent |
| Yellowing | Minimal | Gradual amber tone |
| Application | Smooth, easy | Sticky, dragged brush |
| Clean up | Soap and water | Mineral spirits |
| Odor | Low | Strong solvent fumes |
How to apply water based varnish
While oil and water based varnishes are applied similarly, there are some key tips for success with waterborne finishes:
– Only apply at temperatures between 65-90°F to avoid blushing issues.
– Let stains dry 72 hours before varnishing for proper adhesion.
– Sand wood to 220 grit smoothness before starting.
– Seal bare wood with oil based varnish first before using water based types.
– Apply thin coats, no more than 3 mils wet thickness.
– Lightly sand with 320 grit sandpaper between coats to ensure bonding.
– Maintain a wet edge to avoid lap marks. Work from one end of the board to the other.
– Hang freshly varnished items vertically to avoid pooling as the finish dries quickly.
– Allow at least 24 hours between coats and 7 days total curing time.
Maintenance and repair of water based varnish
To keep water based varnish looking its best:
– Dust frequently with a clean soft cloth.
– Clean occasionally with a mild soap and water solution. Avoid abrasive cleaners.
– Place felt pads under furniture legs to prevent scratching.
– Reapply 1-2 fresh coats of water based varnish yearly in heavy use areas.
– Limit direct hot sunlight which can cause premature yellowing.
– Repair minor scratches by lightly sanding the damaged area and brushing on new varnish.
– Completely strip and refinish the surface if extensive damage occurs.
Conclusion
Water based varnish provides a low odor, low VOC option that works beautifully for many interior wood projects. While not as hard and durable as traditional varnish, it resists yellowing, dries quickly, and cleans up easily with soap and water. Pay close attention to proper application techniques to ensure best results. Limit use to indoor furniture, children’s items, cabinets, trim, and other projects that won’t encounter heavy wear. Consider oil based varnish for tabletops, flooring, outdoor furniture, or any highly used surfaces where maximum toughness is needed. By understanding the tradeoffs and ideal uses for waterborne varnish, you can decide if it fits your next wood finishing job.