Last Updated on April 26, 2023 by Ernest Godia
Polyurethane and lacquer are excellent wood finishes. One, polyurethane, is popular among DIYers because it is more user-friendly. The other, lacquer, is more popular among professionals because it is quicker to apply, saving them time.
But can you put polyurethane over lacquer when refinishing a lacquered piece of furniture?
This is a popular question among DIYers. This post will answer it in detail and provide all the options regarding polyurethane over lacquer.
Can You Put Polyurethane Over Lacquer?
The simple answer to this question is, No! You can only repair a lacquer finish with more lacquer. Adding a polyurethane finish to the lacquer beats the logic as the two are incompatible, and the new finish won’t adhere properly or last.
Alkyd varnish is better if you need to paint over the lacquer. Alkyd varnishes adhere better to lacquer than polyurethane. In addition, its finish is similar to lacquer and is less likely to fade.
If you must use polyurethane, you’d have to sand down or strip off the existing lacquer finish to bare wood before refinishing it with poly.
This article provides details on lacquer, polyurethane, and alkyd varnish. It also explains how and why alkyd varnish is better than polyurethane when painting over lacquer.
This should help you go about your project successfully.
What is Lacquer?
Lacquer is a synthetic coating commonly used as a wood finish. It is composed of resin or cellulose ester and, in some cases, both dissolved in alcohol. Lacquer is easy and quick to apply.
It is also fast-drying, giving the furniture a smooth and shiny finish in little time.
The technique of wood lacquering has been around for ages and is currently considered stylish on expensive furniture as it leaves surfaces smooth and glossy.
Lacquered furniture is impervious to water, durable, and versatile because it fits both traditional and contemporary styles.
Lacquer can mimic high-end wood finishes like mahogany, walnut, or cherry. The coating protects surfaces from abrasions, grit, and wear and tear.
Below are the primary lacquer variances:
1. Acrylic Lacquer
Wood tends to turn yellowish with time despite using a finish. Acrylic lacquer is resistant to the yellowing effect and leaves a clear coat on furniture. The product is costly but resistant to scratches and wears, making it worth the money.
To apply the acrylic lacquer, you’ll need to combine it with a thinning agent before spraying it on the intended surface.
CAB-acrylic lacquers fall under this class and are well-known for their flexibility compared to traditional acrylic stains.
2. Nitrocellulose Lacquer
Initially, nitrocellulose lacquer was used on automobiles before making its way to furniture. It is known for its evaporative nature and color enhancement on light and dark wood furniture.
It is resistant to damage, making it an excellent protective coating. However, it is best to use it in a well-ventilated room and exercise caution when spraying nitrocellulose lacquer as it’s highly flammable.
3. Water-based Lacquer
The water-based lacquer is cheaper, fast-drying, less toxic, and odorless. In addition, it can last several years longer than a nitrocellulose lacquer and an oil-based finish.
4. Urushi Lacquer
Urushi lacquer, or Japanese lacquer, is made from sap extracted from the Urushi tree, which grows in Asia.
The liquid product is poisonous to the touch, causing skin rashes, and has toxic fumes. The extraction process has improved tremendously over time, making harvesting safer.
The resin undergoes treatment, filtration, homogenization, and dehydration, and the end product is a transparent sap.
You can use the liquid as it is or tinted in brown, green, black, red, or brown to match your décor.
5. Catalyzed Lacquer
Catalyzed lacquer is available as acid-catalyzed lacquer (AC lacquer) and pre-catalyzed lacquer (Pre-cat). AC lacquer is a two-component system typically cured with an acid catalyst hardener solution you’ll add before application. The coating is durable, fast-drying, and easy to apply.
Pre-catalyzed lacquer is a one-system component, meaning the hardener is added during manufacturing. The coating is beautiful, damage resistant, long-lasting, and safe for food contact, making it ideal for kitchen cabinets. You use the Pre-cat straight out of the tin without pre-mixing.
What is Polyurethane?
Polyurethane is a synthetic plastic in liquid form that gives furniture a thick and glossy finish. You’ll have to use a brush or roller while applying it. Its coat is thicker and more durable, making it ideal for outdoor furniture.
The two variants of polyurethane are:
1. Oil-based Polyurethane
The oil-based polyurethane creates a firm and protective coat on surfaces. It is durable and can withstand the elements, making it a good outdoor choice.
However, it takes over 24 hours to dry, so woodworkers with limited time prefer water-based polyurethane.
The oil-based polyurethane has a strong odor, and its fumes are toxic, so it is best to use it in a well-ventilated area.
2. Water-based Polyurethane
The water-based polyurethane is popular as it dries faster, is less toxic, and is odorless than its counterpart. But, water-based polyurethane is less resistant to heat than its oil-based cousin. So it may not be ideal for kitchen tabletops and outdoor furniture.
Read our article for a detailed comparison of water-based polyurethane vs. oil-based poly.
How Many Coats of Lacquer On Wood?
You’ll need 3-5 coats of lacquer to get a smooth feel and shiny finish on wood surfaces when brushing it on. If spraying, apply 6 to 9 coats, depending on how generous you feel, for extra protection and durability.
Lacquer dries very quickly, taking roughly 10-20 minutes to dry. However, wait at least 60 minutes for each layer to dry before applying another.
The initial 2-3 layers are sealer coats, the subsequent 2-3 layers are built coats, and the last are final coats. Some light sanding is recommended after 2-3 coats.
Lacquer is thin and quickly penetrates the wood pores, enhancing the wood grains. It is best to apply thin coats of lacquer with a sprayer or brush.
Applying lacquer with a brush works best in small projects. It dries quickly, making it impossible to work your brush over extensive areas and maintain a wet edge.
For an even coat, you can purchase lacquer in spray cans or load your lacquer into an HVLP sprayer. The HVLP will cost you hundreds of dollars, but you use less lacquer in contrast to using it as an aerosol.
In addition, the sprayer applies the finish uniformly, making it a better alternative.
- Move your sprayer or spray can in sweeping motions over the wood for the best outcome.
- Keep a steady hand and spray at a consistent angle.
- Consider overlapping over 50% as you apply the lacquer.
- You don’t need to sand between each coat, as lacquer contains a solvent that melts the top layer into the bottom, creating a smooth finish.
- Level and rub out the finish to eliminate imperfections and maintain a consistent sheen.
- Leave 4-6 millimeters for a refined finish. (Manufacturers write the recommended dry film thickness on the label).
Does Lacquer Scratch Easily?
Well-applied lacquer doesn’t easily sustain scratches. The tendency of lacquer to scratch depends on the following factors:
- Wood type
- Wood condition
- Application technique, and;
- Type of lacquer.
A thick coat of lacquer is prone to scratches. It is best to apply thin layers as they dissolve into each other, resulting in a uniform finish.
If you notice scratches on your painted surface, lightly sand them off or buff them with a dry rag or lint-free cloth. Dust off and apply another coat of lacquer.
Thin coats of lacquer rarely scratch easily. Consider thinning your lacquer by mixing it with a thinner.
Catalyzed lacquer provides a durable coat that is resistant to scratches. Use a lacquer thinner or mineral spirits to test whether you work on catalyzed or regular lacquer.
How to test whether you have catalyzed or regular lacquer
- Dip cotton swabs into a lacquer thinner and dab it over a particular wood portion.
- If the lacquer gets sticky, that’s regular lacquer, and if the thinner has no effect, you are working on catalyzed lacquer.
Essential care tips for lacquer
- Avoid placing heavy items on lacquer tops and use rubber mats under decorative pieces to prevent scratches.
- Wipe off spillages immediately as water damages lacquered furniture. Keep your lacquered pieces dry.
- Regularly dust the furniture to avoid accumulation. Use a soft cotton fabric or feather duster.
What Can I Apply Over Lacquered Surfaces?
Since polyurethane won’t stick to lacquer and peels off over time, alkyd varnish is the best choice.
Alkyd varnish has a natural look and glossy finish like lacquer. In addition, it is more resistant to fading. Pick an alkyd varnish that matches the lacquer for the best outcome.
Alkyd varnish comprises polyester resins derived from vegetable oils and modified with fatty acids. The varnish is quick-drying, durable, and offers protection against UV light, heat, and water. The varnish is relatively clear and ideal for interior and exterior wood.
Alkyd varnish adheres better on lacquer than polyurethane and is more immune to wood’s yellowing effect. In addition, due to its clear natural appearance, alkyd varnish enhances wood grains and color, improving its aesthetic value.
You can apply alkyd varnish over lacquer but not vice versa, as lacquer contains a more potent solvent than the varnish. The lacquer will dissolve and eat away the finish underneath.
How To Apply Alkyd Varnish Over Lacquer
Below is a detailed step-by-step procedure for applying alkyd varnish over lacquer.
Supplies needed
- Alkyd varnish
- Naphtha
- Drop cloth
- Damp lint-free cloth
- Fine grit sandpaper
- Sprayer
- Natural bristle brush
- PPEs
- Thinner
STEP 1: Determine the type of lacquer used
Rub a cotton swab dipped in lacquer thinner or mineral spirit over the wood to determine whether your lacquer is catalyzed or regular.
If the lacquer gets sticky, that’s regular lacquer, as catalyzed lacquer doesn’t react to the thinner or mineral spirit.
Catalyzed lacquer is strong and durable and doesn’t need a protective coat.
STEP 2: Prep your working area
Cover your working area with a drop cloth to avoid splashes, drips, or gloss spillages on other surfaces. Clean the piece of furniture you are working on and let it dry before you proceed.
STEP 3: Clean the wood with naphtha
Use naphtha to remove wax, oil, crayon marks, or polish on the surface, which evaporates rapidly.
Naphtha is a strong solvent but not concentrated enough to damage the lacquer finish.
STEP 4: Lightly sand the wood surface to scuff it up
Excessive sanding can affect adhesion, appearance, and film build. Scuff sand the furniture surface to remove any imperfections and prep the wood for better gripping of the varnish to lacquer. Scuff using a fine 400-grit sandpaper and a light touch.
STEP 5: Wipe away the sanding dust
Use a damp, lint-free cloth or rag to wipe dust off the roughed-up surface. You can dust with clean air if you don’t have a tack cloth.
STEP 6: Apply the varnish
When applying the varnish, use a natural bristle brush, roller, or conventional spray. Reduce the first layer of varnish to 10% with a thinner. Thinning helps the initial coat bond better to the lacquer, reducing bubbles and runs on the piece.
When using a brush or roller, move it consistently, making gentle strokes. Excessive brushing causes bubbles or craters on the wood.
For the first coat of varnish, apply against the grain, then a follow-up coat with the grain.
On the second coat, use undiluted varnish and brush as you did the first coat. Let each coat dry for at least 18-24 hours before adding another layer.
Lightly sand between coats and wipe the dust with a tack cloth.
Pay attention to the manufacturer’s instructions on application and drying time, as that affects the durability of the varnish. Also, exposing the varnished furniture to direct sun, high temperatures, or high and low humidity can have adverse long-term effects on the finish.
Can I Stain Over Lacquer Finishes?
It’s impossible to stain over lacquer. Like any protective coat, lacquer hinders the stain from penetrating the wood. Stains drip off or bead up over a lacquered piece. The only way to stain lacquered wood is to strip off the lacquer first and restain the piece.
Here is how to stain lacquered furniture:
- Prepare your workspace by laying a drop cloth to prevent the area from stains and drips. Also, wear your protective gear, as the products you work with may be toxic.
- Strip the lacquer and stain. While stripping the lacquer, some stain is lost with it. Apply the stripper and let it sit until the lacquer starts bubbling.
- Scrap off the surface with a paint scraper or putty knife to get rid of the lacquer.
- On the sides of the wood, use a gel-based stripper to avoid gross spillage.
- Sand the surface with a sand bar or power sander until you expose bare wood.
- Clean the residue with a damp rag dipped in 1 cup of tri-sodium phosphate and 4 gallons of water. Scrub the wood surface and let the solution dry off.
- Restain the wood and seal it. Spread the stain over the wood with a brush, rag, or roller. Work in small sections and keep wiping off the excess product to prevent it from forming pools on the surface.
- If you are content with the final look, let the stain dry. You can add a protective topcoat of your choice.
Why is Alkyd Varnish Better Than Polyurethane Over Lacquer?
Below are reasons why alkyd varnish is superior to polyurethane when coating over lacquer:
- Alkyd varnish contains polyester resin which helps it adhere to the lacquer, unlike polyurethane which doesn’t grip and eventually peels off.
- Alkyd varnish has a clear and natural appearance giving the furniture a finish that matches the lacquer.
- Alkyd varnish is immune to the yellowing of the wood, making its finish more durable and protective.
Differences Between Polyurethane and Alkyd Varnish
Here are the significant differences between polyurethane and alkyd varnish:
Durability
Polyurethane is more durable than alkyd varnish. It provides wooden surfaces with a harder protective coating. Polyurethane can handle heavy traffic without scratching or forming abrasions.
Alkyd varnish is less durable. However, it is flexible and immune to cracks and UV damage.
Application
Applying polyurethane is easier by using a brush, spray, or wipe-on. You need 2-3 coats of poly, and you are good to go.
Applying alkyd varnish needs a bit of skill and experience. Also, the surface must be clean and dry, as any particles will affect the adhesion. Clean off grease and dust by solvent wiping for better application.
Drying time
Water-based polyurethane dries quicker than oil-based polyurethane.
Alkyd varnish takes 3 hours to dry to touch, 24 hours for you to handle the wood, and 18 hours before you can recoat.
Toxicity
Both polyurethane and alkyd varnish are toxic, and you’ll need protective gear. However, polyurethane is the more harmful of the two.
Price
Polyurethane is more expensive than alkyd varnish due to its durability. The cost of alkyd varnish depends on the type and brand, but it is relatively cheaper.
Can you put polyurethane over lacquer: FAQs
We’ve answered some of the frequently asked questions to make your search easier:
Can you put anything over the lacquer?
Not everything can go over lacquer, as it won’t bind and will eventually peel off. However, alkyd varnish contains polyester resin allowing it to adhere to lacquer. You can also paint over lacquer after covering the entire surface with a primer.
Is polyurethane stronger than lacquer?
Yes, polyurethane is more potent, thicker, and durable than lacquer.
Lacquer is thinner and relatively durable. It is prone to abrasions, scratches, and yellowing over time.
Can I apply varnish over lacquer?
Yes, varnish can go over lacquer as long as they are compatible. After the lacquer has cured in about 48-72 hours or 7 days, you can add a marine spar varnish, depending on your preference. The marine spar varnish gives lacquer additional protection against sunlight and heat damage.
Alkyd varnish also goes over lacquer if you aim to restore your lacquered pieces.
Can lacquer go on top of polyurethane?
You can get away with spraying lacquer over polyurethane if you are working on an old piece of furniture. However, applying the lacquer on top of a fresh coat of polyurethane will result in lifting.
The ideal way to do it is to add a layer of dewaxed shellac over the poly, then spray the lacquer on top.
Does water damage lacquer?
Severe water damage turns lacquer milky and hazy, known as “blushing.” Leaving hot or wet glasses on lacquered surfaces without coasters tends to form white rings.
You’ll need to find a way to allow the water to evaporate to correct blushing and water damage. If you find it impossible to control the humidity, use a retarder to slow evaporation time. Mix lacquer with the retarder and spray a fresh coat on the piece.
Can You Put Polyurethane Over Lacquer: Bottom Line
There are better choices than polyurethane if you want to add a protective coat over your pieces. Polyurethane doesn’t adhere to lacquer; if you apply it anyway, it peels off with time.
Alkyd varnish is a better choice as it adheres to lacquer, creating a durable bond. In addition, the alkyd varnish gives the wood a lacquer-like finish.
Regular lacquer is fragile and may need extra protection over time. To restore your lacquered furniture to its original glory, try layering it with an alkyd varnish coat.
We hope this article has addressed most, if not all, the challenges you might encounter on your project. In the comment section below, let us know your experience putting polyurethane over lacquer.
