Yes, varnish is waterproof and is a commonly used wood sealant thanks to its waterproofing properties.
There are various types of varnish so to get the best results it’s important to choose one based on your needs.
As wood is porous, a layer of varnish is often required to protect and maintain the wood.
The type will depend on the wood and the situation, something we discuss more below.
What is Varnish?
Varnish is a waterproof coat that is usually transparent and forms a protective layer when applied to wood and other materials.
The combination of resin, solvent and drying oil found in varnish allows it to dry hard producing a scratch-resistant shell that protects the material from water.
Types of Varnish
There are different types of varnish so the type you use will impact the end results.
Some varnish is meant for interior use and provides a polish rather than a protective layer.
A good example of this is Spirited varnish or French-Polish that is used for polishing woodwork that is kept inside.
For waterproofing, look for exterior varnish, polyurethane varnish or marine varnish.
Remember that certain types of varnish will provide a higher level of waterproofing than others.
Polyurethane varnish usually has UV blockers that help to protect wood from UV.
This is a good choice for outdoor furniture or wood that is exposed to sunlight as the varnish will prevent the colour from changing or fading over time.
Polyurethane is also a good choice for wood floors as it is hard and protects against abrasion.
Whatever varnish is being used it is essential the varnish dries completely before being exposed to water.
It’s also important to be aware that the varnish can become worn and the waterproof properties will become less effective over time.
Always check the individual product for reapplication instructions.
Benefits of Varnish
As well as being waterproof, varnish helps to enhance the appearance of wooden items.
A couple of coats of varnish will help the wood to last longer and look better.
Varnished wood is also easier to clean and maintain.
Unfinished wood is porous so it picks up bacteria easily and will absorb moisture from the air, this is why unfinished wood is more likely to warp or split over time.
A layer of varnish stops the wood from absorbing water from the air, weather or accidental spills.
Water-Resistance Vs Waterproofing
It’s important to waterproof the wood rather than only make it water-resistant.
Wood that has been treated with a water-resistant coating will still soak up water and become damaged if exposed to water over time.
Whereas wood with a waterproof coating (varnish) will not soak up any water at all.
This is why it’s vital to pick a varnish type that is waterproof and designed for the planned use.
Wood Oil Vs Varnish
Oil-based products are popular as they are easy to use, help to fill in cracks and are able to restore the look of the wood. Wood oil dries hard so makes the wood easy to maintain.
While oil is a natural solution for finishing wood, most oil-based products offer a level of water resistance rather than complete waterproofing.
They also don’t provide a glossy finish like other varnish products do.
Varnish, on the other hand, is a waterproofing solution that dries quickly, gives wood a rich colour and is easy to maintain.
The downside to varnish is that it is often made up of chemicals and produces fumes when wet. When looking for a varnish, choose one that suits your use.
For example, some varnish products are designed for use outdoors and, as such, they offer additional UV protection as well as waterproofing properties.
You can also find products that offer a combination of sealant and stain. These are a good option for waterproofing wood while also achieving the colour and finish you want.
A waterproof sealant-stain can be water-based, oil-based, or alkyd-based and also contain pigments.
There are interior sealant-stains and exterior ones so choose one based on your requirements.
These combination products dry quickly, are easy to maintain and come in a wide range of colour options.
They offer good protection and can usually be used without the need for a primer.
You will have to reapply this finish every few years to keep the wood protected.
Varnish is an effective and easy to use waterproofing sealant. You will find a range of different varnishes available so be sure to choose one that suits your application.