Definition: the final layer of coating after stain or paint used to seal and protect the finish
Why does your finish need a topcoat?
Whether you’ve painted or stained, your piece needs a topcoat to both seal the paint/stain and protect it from use and damage. These topcoats guard it against stains, water damage, and natural wear and tear.
When you’ve put so much hard work into refinishing a piece, you want to make sure that it will maintain that beautiful finish for years to come.
Types of topcoats
Polyurethane
Polyurethane (oil based):
- slightly darkens and enhances the wood grain (wouldn’t use on light paint colours)
- cleans up with mineral spirits
- very durable, making it the best choice for furniture that gets a lot of use
Polyurethane (water-based):
- dries quickly
- dries clear
- less hard on lungs and nose when applying
- cleans up with soap and water
Polycrylic
- always water based
- leaves a clear, non-yellowing surface on light surfaces
- far less smelly and toxic than either type of polyurethane
- dries very quickly, although it can take a long time to fully cure for use
Varnish
Varnish is a sealant composed of specific resins, oils, and solvents that creates a translucent, highly protective coating when applied to wood. Early varnishes were solutions of natural resins that are the secretions of plants.
- consists of a resin, a drying oil, and a thinner or solvent
- higher ratio of solids, making it more resistant to water and less susceptible to ultraviolet light
- can be tricky to use, as the liquid has a tendency to bubble up while being applied
- can take a long time to dry (at least six hours for each coat)
Many different types of varnish: spar, exterior, alkyd, oil, acrylic, bituminous, spirit.
Water-based varnishes are becoming an alternative to solvent-based varnishes. They consist of acrylic resins which have been dissolved in water, making them a safer choice.
Lacquer
Lacquer is a type of solvent based product. It is a range of clear or pigmented coatings that dry by solvent evaporation to produce a hard, durable finish.
- fast drying
- impervious to water
- maintains its transparency as it ages
- usually sprayed on instead of brushing because it’s thinner than other finishes
- can be difficult to remove scratches or dents
- over time it can begin to discolor
- a respirator and well-ventilated area when applying are an absolute MUST due to the toxic nature
Lacquers have three basic classes: nitrocellulose, CAB-Acrylic, and Catalyzed. The nitrocellulose is essentially the “everyday” lacquer that you’ll find in most hardware stores. It’s this class that tends to yellow over time.
Shellac
Shellac is a resin secreted by the female lac bug on trees in the forests of India and Thailand. It is processed and sold as dry flakes and dissolved in alcohol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish.
- a natural finish that has been used for thousands of years
- an evaporative finish
- has a warm, amber color
- dries quickly so multiple coats can be applied in one day
- has less durability than other topcoats as it can be damaged/removed with alcohol
- naturally contains small amount of wax (3%–5% by volume)
- when shellac is used as a primer, sealer or in between coats of a different type of finish (lacquer, polyurethane, etc.), dewaxed shellac should be used because those other finishes cannot stick to wax
Furniture Wax
Furniture wax seals for protection and intensifies the colour of painted furniture while giving a very durable finish. It dries to a velvety smooth matte finish and more sheen can be achieved by buffing.
- made with natural ingredients
- can use on any porous surface
- can come in clear and tinted forms such as white, antique and black to achieve different finishes
- should not be used on paint that has an acrylic or latex base; these are not porous so the wax has nothing to absorb into
- once cured, is waterproof
Liquid wax is well-suited to furniture that has a lot of intricate details or interesting shapes because you paint it on. Paste wax is better for smooth surfaces but harder to apply and needs elbow grease.
Comparison of products
There is no one product that is better – it’s really up to your personal preference, the finish of your piece and the level of protection you are looking for.
The products I use
Hands down, my FAVOURITE top coat is General Finishes High-Performance Topcoat. It has also been chosen as the Winner of Fine Woodworking’s “Best Overall Choice Award”- voted as the hardest, most durable consumer polyurethane topcoat. Bob Vila also awarded it as “Best Overall” in water-based polyurethanes.
Best of all, I have never found it to yellow!
I love the soft, velvety feel that wax gives over chalk/ mineral paints. When given the appropriate time to cure, it is very durable!
It can be intimidating to use at first but once you get the hang of it, it’s quite easy to apply. Here’s a link to how I apply it: click here
Methods for applying topcoats
Brush- This set by Zibra has engineered natural filaments designed to give you the smoothest topcoat finish. It is recommended to use natural bristle for oil-based finishes, synthetic bristle for water-based finishes.
Sponge- This one by Country Chic Paint is perfect if you want to apply incredibly smooth, thin coats especially on tricky areas like chair spindles.
Spray gun- By Wagner, this one has contactless coating for varnishes so you can achieve even and complete surface protection.
Foam brush- designed to absorb and hold all types of paints, stains, and urethanes; gives a smooth finish and are priced to throw away after the job is done.
References:
https://www.ehow.com/about_5044720_nitrocellulose-lacquer.html
https://generalfinishes.com/wood-finishes-retail/water-based-topcoats-and-sanding-sealer/high-performance-polyurethane-water
https://www.hgtv.com/how-to/home-improvement/what-s-the-difference-between-polyurethane–varnish–shellac-and
https://www.spectrumpaint.com/resource_blog/resource_blog_posts/view/143/advantages-of-pre-cat-lacquer-vs-traditional-lacquer
https://www.bobvila.com/articles/how-to-apply-polyurethane-sealer/
https://www.wagner-group.com/en/do-it-yourself/products-and-accessories/product/woodmetal-sprayer-w-150/
https://shop.countrychicpaint.com/painting-sponge/
https://www.enjoyzibra.com/products/top-coat-paintbrush-kit-3-piece
https://www.bobvila.com/articles/best-brush-for-polyurethane/
https://www.bobvila.com/slideshow/the-perfect-paintbrush-and-how-to-choose-it-45583
https://www.bobvila.com/articles/how-to-apply-polyurethane-sealer/
https://abutterflyhouse.com/wood-stain-vs-varnish/
https://www.wikihow.com/Clean-a-Varnish-Brush
https://www.woodguide.org/guide/furniture-wax/
https://walrusoil.com/products/furniture-wax
https://sawsonskates.com/shellac-wood-finish/
https://thewoodwhisperer.com/articles/different-types-of-lacquer/
https://generalfinishes.com/faq/which-topcoat-should-i-choose
https://www.thespruce.com/types-of-wood-finishes-5546952
Kristin Lia Restoration 