Varnish is one of the types of wood finish that has been around for centuries. The word varnish has become a generic term to call other wood finishes like shellac, lacquer, or polyurethane as varnish. It combines oils, solvents, and resins to give the wood surface a clear and lustrous finish. Varnishes contain similar components in paints that deter dust particles, moisture, and grime from sticking.
What is Varnish?
To give you a better understanding of varnish, we must discuss its definition. Varnish is a protective finish containing a transparent, film-like coat in wood for building structures and furniture making. Usually, varnish gives a glossy, semi-gloss, or satin sheen due to its flatting agents. Early varnishes were a combination of alcohol and wood sap.
Manufacturers use solvent or thinner, resin, drying oil, and metal drier to make varnish. There are many types of varnish, and each type has unique components, chemical reactions, and drying time.
The solvent evaporates, allowing the varnish to dry during the curing period. If using resin varnishes, you will notice that it hardens quickly once the solvent evaporates.
Waterborne and acrylic varnishes dry when the water evaporates, but the curing period could take longer. It is because the latex particles absorb the organic solvents, resulting in the long process of evaporation and curing.
Epoxy, oil-based, and polyurethane varnishes do not turn into liquid after the solvent evaporates. Still, curing begins immediately and undergoes several changes: liquid to syrup, tacky to sticky, dry gummy to dry before it hardens.
Factors Affecting Drying and Curing
Different types of varnishes have different reactions and curing periods due to their compositions. But environmental factors significantly influence how they evaporate and dry. The wood’s exposure to sunlight, heat or ultraviolet can speed up the drying and curing period of all types of varnishes.
Benefits of Using Varnish on Wood
Varnish offers several benefits for your woodwork or furniture project. Here are the benefits of using varnish in your workpiece.
Offers Protection
A well-varnished piece of furniture does not require regular maintenance like repair or coating. It prevents the wood surface from accumulating dust and moisture, contributing to its deterioration. All you need to do is to wipe the surface of your table, cabinet, doors, or chairs with a dry cloth to remove the dust.
Extends the Life of the Wood
Varnish is a sealant and protective film against abrasion, stains, heavy pressure, and heat. The wood surface protects from alkaline or acidic substances, heat, alcohol, moisture, humidity, and water vapor.
It covers the workpiece from warping, fiber erosion, abrasion, expansion, or shrinking. Varnish discourages the growth of harmful organisms, such as molds, mildew, bacteria, bugs, fungi, and termites, giving more years of life to your wood.
It Highlights the Wood’s Beauty
The varnish composition enhances the wood grain’s natural color and beauty. Several varnish coatings highlight the wood pores, bringing back their luster and natural look.
Varnish protects the painted surface from atmospheric elements and makes the surface easier to clean.
Offers Protection to Painted Objects
Dust accumulates on art collections like paintings over the years of hanging. Applying the varnish over a painted wood protects the grain from atmospheric and environmental conditions.
Varnish creates an even sheen over the entire surface of the picture. A double layer of varnish will even out the image’s final appearance, giving it a consistent overall look.
Adding a coat of varnish over the painting helps restore its original look. It also brightens the aesthetic appearance of the unpainted wood surface by creating an even luster on the entire image.
Applying a double coat of varnish on the painting gives a consistent appeal, giving it a fresh new look.
Gives Aesthetic Appeal
Your woodworking project requires varnish to enhance the natural beauty of the wood grain, or you can apply it over a coat of paint for color variation. It improves the grain and color of the wood. It is an excellent wood finish for rustic, cottage, Victorian, or vintage-style homes.
Offers Health Benefits
It also offers health benefits to homeowners by improving their mood and enlightening their spirit when looking at the varnished woodwork.
Different Types of Wood Varnish
1) Floor Varnish
Floor varnish enhances the grain and natural character of your wood flooring. It protects the floor from wear and tear, especially in areas with heavy traffic. Using a high-quality floor varnish will maintain its luster and sheen for years. For daily care, wipe the floor with a dry mop to keep it in tip-top shape.
Floor varnish offers protection to the floor surface from abrasion, bruising, and stains due to its clear coats that can be water-clear or oil-based clear finishes. Both finishes leave a lasting glossy, shiny, and transparent finish on your wood flooring.
These clear coats consist of single or two-component coating. They are also available in pigmented with dyes to give color to stained floor surfaces.
The varnish becomes tarnished when a sharp or heavy object drops on the floor, splitting and chipping the wood surface. The changes on the floor surface become noticeable in the long run.
The downside of floor varnishing is that it could wear out over time due to dirt particles and abrasive objects carried by the wind and feet of humans and pets.
2) Acid-based Wood Varnish
The acid-based wood varnish is suitable if you want a clear and protective finish on your wood furniture or want to change your floor’s color. The coatings can either be clear or tinted with pigments or color dye.
Acid-based varnish dries quickly due to its low viscosity. The layers seep into the wood pores and grains, leaving a resilient finish. The wood can stand against direct sunlight, moisture, and humidity.
3) Acrylic Varnish
Acrylic varnish is a non-toxic varnish comprising water, solvents, and acrylic polymers. A clear coat depends on the amounts of these components, which impacts their performance on the wood surface.
If the amount of solvents and water is high, the ability of the polymers to pull together becomes lesser. The higher the acrylic polymers, the more precise the film coats the surface of painted woodwork or artwork.
The acrylic polymer particles bind well after applying the varnish to the wood surface, as the solvent and water slowly evaporate. Use a spray or paintbrush to apply the acrylic varnish on the wood surface. Sprays are safer to use as the job is quick, and varnish foaming does not occur.
Acrylic varnish is resistant to UV light, which is ideal if using wood outdoors. Its versatility allows it for other uses, such as coating for paintings and artworks.
There is a wide range of acrylic varnishes in the market, and they are available in matte, satin, and gloss finishes. The good side of this varnish is they do not turn into a yellowish tint over time. Their downside is it does not penetrate the wood pores.
4) Spirit Varnish
Spirit varnish is also known as French polish. Its use in woodworking and musical instruments has been around for hundred years ago. The varnish contains about 30 and 40 percent natural resins, while ethyl alcohol includes 90 to 95 percent.
The substances in spirit varnish consist of natural resins like acaroid resin, rosin, mastic, sandarac gum, soft copals, and shellac. It also contains synthetic phenol formaldehyde novo lock resins. Its resilience to wear and tear is due to the presence of other substances that undergo plasticization. Among these substances include fatty acids from linseed oil and castor oil.
Spirit varnish has a protective film that seals the wood and enhances its natural beauty. Use a cotton wad or paintbrush to apply the varnish on the wood. Apply several layers at intervals of up to ten minutes. The solvent’s solubility stays in ethyl alcohol, producing glossy film-forming during evaporation.
Acrylic varnishes are a popular choice in varnishing violins. Some people think that spirit varnish is the same as shellac, but they are different. Spirit varnish has a thinner consistency, causing it to smudge when you overapply it, while shellac has a waxy texture that does not smear.
5) Water-Based Varnish
Water-based varnish is an organic and food-safe varnish that offers an alternative option to solvent-based varnishes. The varnish contains acrylic resins dissolved in water, which works similarly to solvent-based varnishes. It is a healthy and environmentally friendly varnish with the same effectivity as its solvent counterpart.
This varnish offers a durable, quick-drying, and odorless method of wood finish. You can clean the dried surface with brushes using lukewarm and sudsy water.
6) Solvent-Based Varnish
The solvent-based varnish offers a clear coat on wood surfaces due to its high level of organic solvents, higher than water-based varnish. The solvents create an obnoxious odor during application and curing time.
Solvent-based varnishes work well if you apply a specialized cleaning method on the wood and allow extra time to dry. The organic solvents make the drying time quicker. It forms a paint film after application, even before it evaporates.
7) Oil-based Varnish
Oil-based varnishes are a product of dissolving hard resins in oil. They are ideal for exposed surfaces that require regular maintenance, like cleaning and polishing. Furniture pieces with oil varnishes get a clear coat, giving them a clean and luster appearance. It is not only wood that can benefit from oil varnishes, but metals and masonry.
There are wood applications that are not suitable for oil-based varnishes. They need to catch up to lacquer and shellacs when it comes to drying time. As soon as this varnish type dries into a hard transparent film, it sticks to the wood for years without fading, leaving it free of abrasion and scratches.
Several coats of oil varnishes offer a smooth gloss finish to the wood. The oil stays and seeps into the grain and pores of the wood when the solvent has dissolved and evaporated. Linseed and tung oils are examples of oil varnishes. They are suitable for wood flooring, furniture, fences, and exterior decks.
8) Alkyd Varnish
Alkyd Varnish is a varnish that offers a clear wood finish. It uses high-quality alkyd resin and is suitable for interior and exterior wood applications. Experts recommend alkyd varnish for prepared wood and natural wood substrates such as softwood, hardwood, and fiberwood. It works best for pine, redwood, cedar, maple, oak, walnut, gum, mahogany, and birch.
The characteristics of alkyd varnish comprise a clear color with transparent gloss, semi-gloss, and a flat surface look. The drying time usually lasts three hours, 24 hours to handle, and 18 hours for recoating. However, it depends on the manufacturer’s instructions. Usually, alkyd varnishes contain vegetable or modified natural oils.
Wooden furniture with alkyd varnish is glossy while bringing out the natural grain and texture of the wood. This varnish has high resistance to harsh conditions, UV light, condensation, water, and moisture, making it an ideal finish for outdoor furniture.
9) Lacquer Varnish
Like oil-based varnish, lacquer varnish is not a varnish. It has become its generic name due to its process of applying the finish using a sprayer. Lacquer varnish quickly dries after spraying. It requires a drying or curing period as varnishes do. Thanks to its solvent base, acetone.
When you want to change the finish, lacquer varnish is easy to remove by applying the wood surface with a coat of lacquer thinner or acetone on a small clean cloth. It is a versatile option for enhancing the look of your furniture and is easy to use if using an aerosolized version.
Lacquer is a combination of pigments, plasticizers, alcohol, and shellac. Its purpose is to create glossy woodwork. It produces a synthetic coating on the wood grain, which gives a high-gloss appearance. Since lacquer varnish contains VOCs, it is not suitable for indoor use.
Lacquer is advantageous because it comes in shades from transparent to multicolors. You can apply it alone or pair it with stained wood.
10) Exterior Varnish
Exterior or outdoor varnish is for outdoor use. This type of varnish has a high resistance to ultraviolet rays and extreme conditions. Their microporous content gives your wooden furniture enough space to breathe and discourages microbial growth.
Exterior varnish has a unique formulation similar to yacht varnish, which can withstand moisture and water. This wood finish maintains and brings out the natural color of the wood. They protect the wood from flaking and peeling but take longer to cure. They are ideal for doors, windows, conservatories, and outdoor structures.
11) Yacht Varnish
Yacht varnish works similarly to exterior varnish as it is resistant to moisture and water. Its invention was to seal the boats to prevent water from seeping into the wood. The varnish is flexible to tackle the pressure from waves.
Applying yacht varnish on furniture does not yield good results if you are after the looks. It does not offer a higher gloss to the wood surface and has little resistance to ultraviolet.
The latest formulation of yacht varnish has improved by adding phenolic resins and tung oil, which gives gloss to the wood. Today, they come in satin and matte finish. It has become a durable varnish that can extend the life of your wooden furniture for years.
12) Shellac
Shellac is not much of a varnish, but because of its method of applying it on the wood surface, it has become classified as a varnish. Whether it is a varnish or not, the vital thing to know is that shellac is a product of harvesting the natural resin from the laq beetle.
Shellac is a wood or French polishing staple that gives a protective film on the wood surface, gold, and metal leaves, like gold over a painting. Early woodworkers dissolved the resin with a solvent to achieve its varnish finish, known for its high gloss finish that can stay for years. Shellac is available in various variants, such as pucks, dry flakes, and polishes.
13) Polyurethane Varnish
Polyurethane varnishes come in different types. They can be water or oil-based, but their primary purpose is to protect the interior and exterior parts of wooden floors and stairs, where their wear and tear is unavoidable due to people and pets going in and out of the area. It is also suitable for hardboard, plywood, parquet flooring, and chipboard.
Using water-based polyurethane varnish for wood finish offers ease of application, and it is eco-friendly compared to solvent and water-based versions, which contain higher VOCs.
The wood finish is suitable for repair, renovation, and restoration in wood structures due to its hardening liquid plastic characteristics. The coating is durable and does not turn into a yellowish tint. Its downside is that it does not offer UV protection if you use it for outdoor structures and furniture.
14) Resin
Resin is also known as gum varnish. It is a varnish of liquid coating containing natural substances from plants or insects dissolved in a solvent or spirit varnish. The solvent evaporates, polymerizing the remaining compositions to create a durable transparent protective film.
The resins commonly used in varnishes include dammar, copal, balsam, rosin, sandarac, shellac, elemi, amber, mastic, benzoin, and lacquers. The solvents could be petroleum-based, turpentine, or alcohol.
Resin varnish can be natural or modified natural resin or synthetic resin varnish. It is natural if the resin comes from living trees or fossils. The modified natural resin varnishes are cheaper compared to oleo resinous varnishes. They undergo heat treatment with glycerine to form a gum.
Synthetic resin varnish is typical in the plastic industry. It uses amino resins, silicon, and nitrocellulose substances.