Last Updated on April 10, 2023 by Ernest Godia
Shellac and polyurethane are household names in wood finishing. Both sealants have distinct advantages regarding protecting hardwood floors, furniture, and other materials.
However, they are not the same. Polyurethane and shellac have unique characteristics that set them apart and make one product more suitable for some applications than the other.
Knowing how these two sealants compare can help you choose better for your wood finishing projects.
This comprehensive guide identifies and discusses shellac vs polyurethane, pointing out their similarities and differences. You will also learn their pros and cons to determine when and how best to use each.
What is shellac?
Shellac is a fast-drying sealant obtained organically from the lac bug resin. Its manufacturing process involves combining a solvent such as alcohol with secretions from the female lac bug, making it a safe product.
The sealant can have a yellow or orange tint, giving wood a warm amber tone. It is best used on lighter woods whose color it enhances.
Shellac is easy to apply and dries pretty quickly, but it offers little durability. It wears out with usage, so it is best used to seal and protect woods that are not subject to heavy usage.
Shellac pros and cons
Pros
- Shellac is fast drying. You can complete the entire wood finishing project in one day when you use shellac.
- It boasts a warm amber tone that can significantly enhance the wood’s natural aesthetics.
- It seals and protects the wood.
- You can use it to seal and protect non-wood projects
- It retains its color for a long time
Cons
- Shellac is less durable than varnish or polyurethane and cannot withstand heavy usage and wear.
- It is susceptible to heat damage. Placing a hot object like a hot mug will leave white rings on the shellac-sealed surface.
- It is also susceptible to chemicals, so everyday household chemical spills can eat through it and damage the surface.
What is polyurethane?
Polyurethane is a highly durable finish that protects wood and other surfaces, including metal and concrete. It is a liquid plastic or synthetic resin that dries to form a rock-solid coat on surfaces.
Its incredible durability and hard-wearing property make it ideal for use on surfaces that experience heavier usage. It also boasts excellent heat and moisture resistance, making it a great choice for surfaces exposed to such elements.
Polyurethane is available in both water-based and oil-based varieties. Water-based varieties are typically clear-colored and fast-drying. On the other hand, oil-based poly has an amber tone and takes longer to dry.
Polyurethane pros and cons
Pros
- Polyurethane is highly durable and long-lasting
- It is available in various sheen levels, including high-gloss, semi-gloss, satin, and matte.
- Both water- and oil-based polyurethane boast incredible resistance to heat, moisture, and chemicals. This property makes it an excellent sealant for kitchen surfaces and other heavier-use areas.
- Surfaces with a coat of polyurethane are hard-wearing and resist abrasion and physical damage well.
- Polyurethane can be used outdoors due to its strength and weather resistance.
Cons
- Polyurethane has a longer drying time than shellac.
- It is generally more challenging to apply than shellac
- Some types of polyurethane turn amber and darken over time.
Shellac vs. polyurethane side-by-side comparison
Both polyurethane and shellac are versatile finishes used on wood and non-wood materials. However, while shellac is typically used on lighter-colored woods, polyurethane is commonly applied on darker woods, but the clear versions can equally work well on lighter wood types.
Read along for a detailed comparison of these two sealants in terms of common uses, durability, drying time, ease of application, and more.
1. Common uses for polyurethane vs. shellac
Shellac is commonly used as a pre-sealant or primer due to its compatibility with a wide range of finishes. It is also used on lighter-colored woods as a topcoat where durability is not a priority.
Shellac also boasts a wide range of uses in food coatings, cosmetics, and dentistry—which are immaterial in our case.
When used as a sealant, shellac does an excellent job of blocking tannins and preventing them from bleeding through the finish.
Polyurethane, on the other hand, is used as a protective topcoat and hardly ever as a primer. It seals and protects wood surfaces in floors, decking, furniture, countertops, cabinets, and more.
You can use polyurethane for indoor and outdoor applications depending on the formula. Usually, the manufacturer will specify on the label if the product is exterior-grade or interior. This should apply to both water- and oil-based poly.
This characteristic sets polyurethane apart from shellac, which is used only on indoor projects.
Verdict: Both products are versatile, but polyurethane wins
2. Polyurethane vs. shellac: Ease of application
You can use a wide range of application methods when working with shellac and polyurethane alike.
For shellac, you can use a spray can, cotton cloth (lint-free), or paintbrush to apply it to your project. If you choose the paintbrush option, ensure it has natural bristles and not synthetic ones for the best results.
Similarly, you can apply polyurethane with a lint-free cotton rag, sprayer, or paintbrush. And thick consistency of polyurethane mean you can also apply it using a form brush, unlike shellac.
Both sealants require a smooth, well-sanded surface. You must also clean and dry the wood before applying shellac or polyurethane to it.
The choice of paintbrush differs depending on the base of polyurethane you are using. Use natural bristles when working with oil-based polyurethane and synthetic-bristled brush for water-based polyurethane.
Like shellac, you must scuff sand between coats of oil-based polyurethane to get the best results.
However, you can get away with not sanding between coats of water-based poly, but we do not recommend it. Sanding between coats is always advisable regardless of the type of polyurethane used.
Read our article on what happens if you don’t sand between coats of polyurethane.
Both shellac and poly require about three coats to create a durable finish, but some thick oil-based polyurethanes can work with just a single coat. However, these are typically more challenging to work with.
Verdict: Shellac is easier and quicker to apply
3. Weather resistance and durability
Both water-based and oil-based polyurethane boast incredible resistance to various weather elements, including UV rays, heat, and moisture. So you can use exterior-grade poly on outdoor wood.
Shellac is more vulnerable to weather elements and cannot be used on exterior applications. The sealer is particularly susceptible to heat damage and will not withstand prolonged exposure to direct heating from the sun.
Polyurethane is also hard-wearing and can withstand incredible levels of abuse indoors and outdoors. This makes it an excellent sealer for high-traffic areas and objects subjected to heavy usage.
Shellac is better used on accent and decorative pieces kept indoors away from heavy usage.
If used in the right environment, shellac provides great resistance to moisture and can keep your wood free from water damage.
Verdict: Polyurethane is more durable
4. Shellac vs. polyurethane: physical properties
Shellac is available as a liquid in most home centers and online stores such as Amazon. It also exists in flakes or solid form. If you buy these instead of the liquid, you must dissolve them in pure denatured alcohol or methanol before use.
Shellac generally has a shorter shelf life, so it is best to dissolve the flakes or open the liquid can when ready.
On the other hand, polyurethane exists as a thick liquid. The product is a liquid plastic, which explains the thick consistency.
Once dry, this viscous resin hardens into a tough, durable coat with a glossy, satin, or matte sheen.
Verdict: Shellac is more volatile than polyurethane
5. Polyurethane vs. Shellac: Drying time
Shellac naturally dries quickly and can work as a wood sealer or finish.
This fast drying time is one of the standout qualities of shellac. The sealant dries in as little as 30 minutes, allowing you to recoat it.
This quick drying time means that you can apply three to four coats in half a day. So you can enjoy faster project completion and shorter turnaround times when using shellac.
In contrast, polyurethane takes longer to dry. It simply won’t allow you to complete the project in one day unless you use the special fast-drying or one-coat varieties.
Water-based poly typically dries in 6 to 12 hours, depending on the weather. Oil-based polyurethane has a longer drying time, taking about 24 to 48 hours to dry.
However, some manufacturers have fast-drying polyurethane variants that take less time to be ready for recoating. A fast-drying oil-based polyurethane can dry in 4 to 6 hours, with similar water-based options drying in as little as 2 hours.
Verdict: Shellac dries faster than poly
6. Colors: shellac or polyurethane?
Shellac is available in yellow and orange shades. It gives the wood a warm amber tone, bringing out its grain and beauty. The sealant can also be medium brown, gold, or blonde, all warm colors.
While shellac’s color is distinct and natural, polyurethane has no specific natural color. Water-based poly is naturally colorless when correctly formulated.
Oil-based polyurethane, on the other hand, has an amber tint, which darkens over time when used on wood and other surfaces.
When used outdoors, polyurethane coatings can become significantly yellow over time due to prolonged sun exposure.
Verdict: Shellac wins the round
7. Polyurethane vs. Shellac: Sheen levels
Shellac creates a glossy sheen on wood surfaces in addition to giving wood a warm amber tone.
Polyurethane offers more variety in sheen levels. You can choose a high gloss, semi-gloss, satin, or matte finish.
This way, you have more variety with polyurethane than shellac.
Verdict: Polyurethane wins
What is the difference between shellac and polyurethane?
The difference between polyurethane and shellac is that polyurethane takes longer to dry while shellac dries quickly. Polyurethane is also a synthetic resin that dries to form a highly durable coat for both outdoor and indoor use. In contrast, shellac is a natural resin used only indoors.
Is shellac good for waterproofing?
No, shellac is not the best waterproofing sealant because it is highly water-resistant but not waterproof. It can withstand water for a few hours but will eventually allow some water damage.
FAQs
Why use shellac before polyurethane?
Shellac is an excellent primer that blocks tannins and prevents them from bleeding through the finish. This can ensure a clean finish with flawless wood color.
What is shellac best for?
Shellac is best used for pre-sealing wood before staining it or applying a topcoat. This helps block odors and prevents tannins from bleeding through the coat of wood stain or topcoat. This ultimately helps ensure a clean finish.
Is shellac better than polyurethane on floors?
No, polyurethane is better than shellac on floors because of its durability and hard-wearing quality. On the other hand, shellac is far less durable than polyurethane and cannot withstand heavy usage, so it is unideal for high-traffic areas like hardwood floors.
Shellac Vs. Polyurethane: Final Thoughts
Shellac and polyurethane are leading products used in finishing wood. However, while polyurethane is perfect for high-traffic areas and items subjected to heavy use, shellac is less durable, making it ideal for coating items subjected to light usage.
So, use polyurethane when coating hardwood floors and outdoor projects. You can also use it as a protective topcoat on darker-colored wood.
On the other hand, use shellac as a pre-sealer or primer to block odors and tannins from bleeding through the wood’s finish. Alternatively, use it as a topcoat when sealing decorative wooden pieces subjected to light usage.
We hope this detailed comparison helps guide and point you in the right direction.
Happy woodworking.