Types of Varnish – Guide to Protective Coatings

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If you are interested in woodworking, a key principle you will have to master is the art of varnishing. Typically made from a resinous material, varnishes are liquids that can be used to dye, finish, and protect both the interiors and surfaces of wooden objects. Not only does varnish offer your wood protection from environmental damage and allow it to last longer, but it can also improve the aesthetic qualities of your finished project. Irrespective of the wood-crafting you perform or of the wood you choose to work with, you will find a myriad of varnishing products designed to protect your timber, increase its lifespan, and leave it looking better. In this article, we will be covering several popular types of varnish, how they work, and how to use them properly. Stick around for more coverage on this topic.

What Is Varnishing?

Put very simply, varnishing is the activity of coating a surface with a material that produces better aesthetics, gloss, and a fair degree of protection for the said surface. Varnishing is typically conducted using a resin diluted in a liquid that can be applied to a surface using techniques very similar to painting.

In the context of wood, varnish is considered to be a form of wood treatment achieved through the application of resinous liquids to the surface of wooden items. After it has been applied, the varnish should permeate through the surface of the wood, into its fibers and thus achieve two things. Firstly, it will alter the aesthetics of the wood with the type of varnish used playing a key role in determining the color. Secondly, the varnish will seal all the pores of the wood’s surface once it has dried.

Visually, varnish appears like a coating of film covering the wood’s surface. Once completely dry, the varnish will be able to disallow dust particles and liquids from seeping into the wood. It is common practice to varnish wooden objects designed for regular use on account of how effective varnish is at increasing the longevity of wooden items. Beyond dust and moisture, varnish also protects the wood from damage that could be caused by exposure to sunlight, abrasion, stains, and impact.

Varnishing Types: A Brief History

The word’s etymology dates all the way back to the era of antiquity when the Greeks used it to describe the amber and sap extracts that can be found in trees. These tree resins were used then, as they are now, to coat wood to change its appearance and protect it from damage.

However, the earliest recorded examples of varnishing stem back from the time of the ancient Egyptians who made use of resins not only to create more resilient wooden tools and objects but also for their signature burial rituals involving mummification. Perhaps the most famous example of varnishing resins being used for mummification would be that of King Tutankhamun, whose remains show signs that the resin used to embalm him was still too high a temperature. This has led many historians to believe that the Egyptian King’s burial was a rushed procedure.

Although we most certainly do not use varnish for the same purposes in today’s world, the types of resins and ingredients present in the ones we use today do not differ all that significantly from the ones used way back then. The first varnishes were composed using tree sap, a naturally forming resin, and a solvent (i.e., the vehicle). These mixtures would be painted into the surface of wood using either a brush or a cloth. Modern varnishes now contain a combination of natural and artificial resins and chemicals to produce a more visually pleasing and resilient coating.

These are not the only examples of the craft of varnishing developing independently during ancient history. More so, wood was not the only thing people knew how to varnish back then. There were also several regions within Asia where formulas containing a complex variety of ingredients were used as a means to apply varnishes to all sorts of surfaces for a large number of practical and aesthetic purposes. Even way back then, we knew how to varnish silk to render the material resistant to water, to maintain a healthy polish of certain precious metals, and even to maintain the combat effectiveness of weapons.

There is no doubt that varnish is a remarkable invention that has seen an innumerable number of applications throughout history. However, this does not change the fact that varnish remains one of the most hazardous materials to work with when treating wood. The reason why varnish can often prove to be dangerous has to do with the fact that most varnishes these days are produced using a tall order of binders and solvents that, apart from being noxious and dangerous to inhale without proper protection, are also highly flammable.

Although varnish is no longer flammable once dried, it does pose health risks when working with it in its liquid state. We would keenly recommend that you make sure that, when you are applying your varnish, you are doing so in a well-ventilated area and that you properly dispose of waste materials and application instruments once the job is done.

Types of Varnish

As alluded to prior, you are spoiled for choice when it comes to picking out the perfect varnish for the job that sits before you. No matter what the task at hand may be, there is an appropriate corresponding varnish. While still falling under the blanket definition of what constitutes a varnish, many demand their own unique application processes to function properly.

Below, you can find a brief breakdown of the types of varnish you will most likely be using as well as the benefits and issues most closely associated with them. We will also indicate to you what applications they are designed for. This being said, we’ve created a short rundown of all of the varnish types you could come across, some of the pros and cons associated with them, and what their intended applications are.

Now that we have established the most common types of varnish that are suitable for application on wood surfaces, as well as their key attributes, feel free to stick with us as we discuss each example in greater detail.

Spirit-Based Varnish

In the treatment of wooden furniture items, we may give turn to a varnish called French polish. All this means is that a spirit-based varnish is being used. French polish has, for hundreds of years, been used to protect wooden objects and tools. French polish was and still is a popular option for the treatment of wood given that it not only makes the wood more resilient to environmental damage but also aids in the improvement of its aesthetic qualities.

While most modern varnishes are produced using a mixture containing synthetic materials, French varnish is unique in that it is produced using the compounds secreted by a specific phylum of East Asian beetle. The secretions released by these beetles appear as a flaky substance that, when diluted in alcohol, produces a varnish suitable for the protection and beautification of wood.

Another commonly associated word for spirit-based varnish would be “shellac”. This, however, is a popular conflation. Shellac and spirit-based varnishes differ in terms of their consistency, with the former being much thicker than the latter. While spirit-based varnish is rather runny, we find shellac to be waxy.  This being said, we do often see crafters using spirit varnish as a primer in preparation for the application of additional varnishes such as shellac. This is especially popular in woodworking projects pertaining to the creation of musical instruments.

The type of finish left behind by spirit-based varnish is that of a thin surface layer with a transparency that does not affect the quality of the texture or the visibility of the grain. Thin as it is, however, this prevents this clear varnish for wood from being able to offer much in the way of protection from environmental factors such as weather and UV rays. This is why you often see this color being used as a primer for more durable varnishes.

Acrylic-Based Varnish

Among the many reasons why varnishes can be dangerous to work with has to do with the fact that they contain volatile organic compounds (VOCs). If inhaled, these chemicals can cause respiratory issues – hence why you are encouraged to always conduct varnishing in well-ventilated areas, preferably outdoors. However, acrylic varnish is an incredibly popular alternative to other more typically risky options of varnish types. This is on account of acrylic-based varnish containing little if any VOCs. Thus, acrylic-based varnishes can be applied indoors if necessary.

What makes acrylic varnish so much safer to use is the fact that it uses water as the vehicle. However, this does not only make it safer to use. Water evaporates incredibly fast, so acrylic varnishes typically dry much faster than their counterparts. If you are working against the clock, this varnish is exactly what you need to be using. Additionally, the acrylic polymer in these varnishes offers substantial protection from UV light. What this means is that it prevents the finish from fading over the course of time.

The finish you can expect from acrylic varnish types is that of a transparent coating that rests snuggly atop the surface it is applied. Both the grain and texture of your wood ought to be unobscured as well. That being said, however, there are still several varnishes of the acrylic variety that are designed to produce different sorts of finishes. Whether you want to stain the wood darker or lighter or retain its natural grade; acrylic varnishes offer you the option for variety.

One primary issue to remain concerned about when working with acrylic varnish is the fact that it can be quite runny and thus difficult to handle on account of it being water-based. That being said, however, water-based varnishes carry a high degree of viscosity and are thus in fact easier to clean up in the event of spillage. Additionally, perhaps the biggest issue with acrylic varnishes that avid woodworkers would jump to address is that acrylic polymer cannot penetrate and disperse uniformly into wooden surfaces. This does have the potential to cause the development of patchiness across the surface of your wood.

Exterior Varnish

As the name clearly suggests, exterior varnish is designed for application to wooden structures meant to remain outdoors. This is an excellent choice of clear varnish to use on wooden workpieces meant to sit in outdoor settings. It offers immense protection against environmental factors such as UV and rain and can also elevate the aesthetic qualities of the wood itself.

If you reside in a region that is host to harsh or unpredictable weather patterns and want to protect your outdoor furniture, you cannot go wrong with exterior varnish. This is particularly the case should you not like the idea of using paint. UV light, rain, moisture of any other kind, and abrasion are prevented by exterior varnish which greatly reduces the chances of your wood either splitting or rotting over the course of time.

Exterior varnish is incredibly hydrophilic, meaning that it is capable of completely sealing the surface and pores of wood and rendering it repellent against moisture. One issue with completely sealing wood, however, is that cutting off the supply of oxygen would lead to the wood becoming brittle over time. Exterior varnish addresses such concerns by allowing the wood to breathe.

If by now you still do not find yourself convinced of the efficacy of this varnish, you must then also take into consideration the fact that exterior varnish also contains chemicals intended to prevent fungal particles from developing on the wood’s surface. These chemicals are referred to as fungicides, which not only protect your wood from fungal infection but also deter infestations of insects such as termites and grubs. But, with great power comes great responsibility and you can expect this varnish to take quite a while to dry.

Polyurethane-Based Varnish

This has got to be among the best options for robust varnishes out there, but such things should be expected from thermoplastics. Durability is the name of the game when it comes to polyurethane (PU) varnish. The coat produced by this varnish is extremely durable and can protect wooden objects from some of the toughest climatic conditions out there. The most typical sort of application for this varnish will be in high-traffic areas.

If you are looking for a strong varnish for outdoor structures, your search ends with PU varnish. The varnish is also remarkably versatile in terms of application potential considering how heavy-duty it is. However, as can be expected of all other forms of polyurethane coatings, this varnish does not protect wooden surfaces by seeping into the pore, instead hardening around the wood and forming a rigid external layer of protection. Like paint, but better.

But since PU varnish cannot seep into the wood, it does not achieve as much of a firm bond with the wood fibers as would be the case with most other kinds of varnish. What this means is that you have to first apply a primer to the surface of the wood. In doing so, you will be guaranteed that there will be enough surface friction between the varnish and the wood to account for proper adhesion. The finish to expect from a PU varnish depends on your choice of product. Typically, we have three options to choose from; satin, matte, or gloss.

What makes PU varnish so remarkable is its list of robust attributes, which trump even those of exterior varnish. Beyond impact, moisture, and abrasion, PU varnish also protects the surface against heat and acids. The one Achilles heel that PU varnish does have, however, is that despite its durability it does not offer much in the way of UX protection. That being said, you can easily account for this by applying PU varnish in thicker coatings. This way is an easy way of minimizing the risk of damage to your surface through exposure to direct sunlight.

Yacht Varnish

If you are more so in the market for a durable yet clear varnish that does not obscure the grain, you could instead look towards yacht varnish. However, you may struggle to find uses for it outside of its primary function. Also sometimes referred to as “spar varnish”, this product was specially designed for use on wooden boat components. More specifically, it was used to protect the hulls and spars of boats, the latter of which are the dense, thick rods of wood on which the sails are supported. Not only is this varnish incredibly durable, but it is also remarkably flexible, which is a great attribute to boast considering how spars and masts tend to bend as the sails catch wind.

Initially, yacht varnish was used on seafaring vessels to protect the wood from water, sea salt, sand particles, and high winds. During the first several years following the invention of yacht varnish, very little attention was given to its aesthetic qualities. Nowadays, however, yacht varnish can be more than just purely functional, coming in a wide variety of colors and sheened finishes. Yacht varnish is still used extensively among boaters to beautify and protect their vessels.

If you have ever been to the ocean on a hot day as a child, chances are your parents insisted you apply sunscreen to protect your skin from sun damage. This same thing applies to wood, with high exposure to UVs resulting in wear over time. Here lies another astronomical benefit of yacht varnish; It is superbly UV resistant as well!

Reflecting on a prior point, however, we must encourage you to think about the pros and cons before choosing to use this varnish for anything besides wood that you expect to be exposed to high volumes of water. For outdoor applications on dry land, we would much rather recommend you use something like exterior varnish. While yacht varnish does supply superior durability, it comes at a high cost that more often than not outweighs the benefits.

Oil-Based Varnish

What is varnishing wood with oil supposed to achieve, exactly? We promise that the more you think about it, the more it begins to make sense. For starters, oil is hydrophobic, meaning it can deter water from seeping into the surface of wood. With moisture protection out of the way, we can begin to consider the aesthetic benefits of all the combinations between woods and oils you could achieve.

Drying Oils

If you have any prior experience in woodworking, you should be no stranger to the concept of drying oils, which are the naturally sourced oils used to varnish wood. This technique was initially discovered in Asia where it was popularized by fishermen who used drying oils to protect their small boats from moisture absorption and damage. These techniques made their way, port to port until they eventually got adopted by the global community. Oil-based varnish remains a popular choice to this day.

There is the argument that drying oils are not true varnishes, per se. A key ingredient in all other varnishes on this list is a solvent of some kind, which dry oils in their pure state lack. While oil may get away with being both the binder and the vehicle in paints, the same rules of definition do not apply when it comes to types of varnish. Thus, oil-based varnishes are typically considered to fall under the category of wood treatment products. While they do provide a small degree of layered protection against basic concerns like moisture, impact, and pests, they cannot compete with the durability afforded by any of the other varnishes on this list.

However, they can help elevate the looks of wooded workpieces and offer a wide range of varnish colors for wood. If you are going for the looks as opposed to utility, we would suggest that you look into oil-based varnishes. Oil varnishes are perfect for indoor wooden furniture that typically remains in a fixed position. Many other wooded household items, features, and decorations can be polished using oil varnish as well.

Drying oils get their name on account of how the oil component of the varnish dries once it has seeped into the wood’s surface and bonded with the fibers. This occurs following the evaporation of the solvent component. The oil will undergo the slow process of oxidation, during which it will begin to set on the wood as it hardens until solid. Drying oils also have numerous other applications as a sealant for a number of other projects, including linoleum flooring.

The use of drying oils to treat and varnish wooden workpieces is a tradition steeped in history, a craft mastered and passed down the centuries. Nevertheless, this classic form of varnishing simply cannot hold a candle to the durability of modern varnishes. Reapplication and maintenance will be frequently required to retain a smooth and undamaged surface. The purer varieties of oil-based varnishes, in particular, offer little to no protection to the wood beneath.

Drying Oils Make Wood Look Good

But while we have plenty of contemporary varnishing products to choose from that outperform drying oil’s durability, there are very few of them that can as effectively help preserve the original, natural tones and textures of wooden objects. In a sense, drying oils are almost similar to leather food in this regard.

Better yet, the process of varnishing wood with drying oils is a relatively easy process. In fact, many woodworkers and homeowners enjoy the process despite the recurrent need for maintenance. One might even go so far as to say the process of maintaining wooden workpieces using drying oils is a ritual that a lot of people find absolutely enjoyable. Especially when working with popular drying oils such as those made of linseed, one cannot help but appreciate the earthy, nutty aromas they sometimes emanate.

Alkyd-Based Varnish

The only difficulty in defining what constitutes an alkyd-based varnish is the fact that it could refer to a varnish from any of the prior categories before. Alkyd, which is a mixture involving vegetables, is an ingredient used so frequently among the many varnish types out there that it warrants its own classification.

Why is alkyd such a popular additive among varnishes? For starters, alkyd can not only improve the durability of a varnish but also decrease the expected drying time. With it also leaving the grain and texture of the wood unobscured, the typically clear finish provided by alkyd also improves the overall aesthetic value of wooden workpieces.

Above all else, however, what makes alkyd such a universally adopted additive is the fact that it affords a substantial improvement to a varnish’s threshold of resistance against fluctuating temperatures and exposure to UV rays. This is a key selling point of alkyd since a core requirement of all varnishes designed to treat outdoor wooden workpieces is for them to offer protection from direct exposure to sunlight. Such an attribute, alongside its exceptional resistance to condensation, makes alkyd the prime option for wooden poolside decks.

Beyond its adequacy for application on wooden objects and furnishing located exterior to the house or anywhere otherwise where it may be in direct sunlight for extended periods of time during the day, alkyd also offers a decent variety of optional varnish colors for wood. Since vegetable oils comprise a large percentage of alkyd’s composition, the combinations and ratios of these oils can be tweaked to produce different finishes that can achieve several aesthetic benefits. Whether you wish to intensify, lighten, or darken your wood’s tone, there is a variation of alkyd-based oil suitable for the job. Needless to say, alkyd is perhaps the most versatile product in the varnishing industry.

Lacquer

Avid wood crafters who have made it this far down the list might begin to cringe at the mere inclusion of lacquer. For people who are well versed in the craft of wood treatment, lacquer is decidedly not considered a varnish despite its similar functionality. This might be because of lacquer’s key superior quality; it is incredibly easy to use. Most varnishes cannot really compare to the ease of use afforded through the use of lacquer, especially given that you can purchase an aerosolized version of the product.

While varnishes tend to provide more resistance against UV rays, lacquer still protects wooden surfaces from moisture, impact, abrasion, cracking, acids, and even alkali. This being said, though, many lacquer products may begin to discolor and turn yellow over time. It can also scratch easily.

But lacquer still has a handful of other redeeming qualities to consider, such as the fact that can be easily maintained or removed. If you are scared of commitment, lacquer keeps the relationship casual by being as easy to remove as it is to apply. This means that you need not worry too much about overapplication or regretting your decisions if you do not like the finished product. You can also always use a bit of acetone to completely strip lacquer from wooden surfaces. There are also lacquer thinners designed specifically for this purpose. And, for the cherry on top; lacquer tends to be very affordable. You are best off using lacquer outdoors, however, since they do contain VOCs.

Wow, we really did not expect this article to be this long, yet here we are! And if you are as well, then we would like to extend our congratulations and thanks! Hopefully, have developed or consolidated your understanding of how to treat wood with several of the most popular varieties of the product. We wish you the best of luck on your future woodworking projects. Just remember that the safest way to apply varnish is by doing so outdoors.

Frequently Asked Questions

What Is Varnish?

Varnish is a resinous liquid most commonly used to treat and protect wood from environmental damage. Varnish can also be applied to wood for the improvement of aesthetic qualities.

Are There Different Varnish Colors for Wood?

There is a vast range of colored and tinted varnishes. Many varnishes are specifically designed to stain or otherwise alter the color of your wood. You can pick and choose between dozens of color options depending on your preferences.