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In this article, we compare and contrast two film-forming wood finishes. Learn the biggest difference between pre-catalyzed lacquer and polyurethane, which is better, and when to use each one.
- What Is Pre-Catalyzed Lacquer?
- What Is Polyurethane?
- Pre-Catalyzed Lacquer vs Polyurethane
- Major Differentiating Factor
- Which Is Better, Pre-Catalyzed Lacquer or Polyurethane?
What Is Pre-Catalyzed Lacquer?
Pre-catalyzed lacquer, also called ‘pre-cat’, is a synthetic finish made from resin dissolved into various polymers and solvents.
Pre-Cat Lacquer Characteristics
It is differentiated from other lacquers by the presence of a chemical catalyst, and has become the new standard in the woodworking industry. It is most commonly applied to wood, although it can also be used to coat plastic and metal.
The catalyst, which is added to the mixture before it hits the shelf, inspires a second phase of hardening called curing. This molecular reaction starts the moment the product is exposed to air, but can take up to 30 days to reach full hardness.
Pre-cat can compete with varnishes like polyurethane when it comes to durability and resistance to impact damage, while still providing lacquer’s signature smooth, ultra high gloss finish. Depending on the resin used and whether pigments are added, the finish could be crystal clear or a vibrant liquidy hue.
Pre-Cat Lacquer Application
Pre-cat lacquer is applied in thin layers to a clean, smooth surface such as MDF, finely sanded wood, or metal. Air-assisted applications such as spray cans and compressed air powered paint sprayers give the best, most even outcome. Brushable pre-cat lacquer is available, but is harder to control.
The first layer of pre-cat lacquer clings to the surface. All subsequent layers adhere to the lacquer below. In order for these bonds to form, the lacquer must be sanded between coats to provide a grippable surface.
Pre-cat lacquer, like other types of lacquer, dries very quickly. All lacquers dry much faster than other finishes like polyurethane.
- Within 5-15 minutes of application, pre-catalyzed lacquer is dry to the touch.
- Then, the second phase of hardening begins, called ‘curing’.
- You don’t have to wait until each layer is fully cured to add another one, but you should treat the finished piece gently for at least the first 30 days.
Air-assisted lacquer applications require thinning the lacquer with solvents like lacquer thinner to produce a viscosity that will not clog the hoses and nozzle. This further speeds the dry time. The temperature, humidity, and fume-content of the environment also affect lacquer’s dry time.
Lacquer retarder is sometimes added to slow down the drying process. Neither thinner nor retarder has any effect on the cure time of pre-catalyzed lacquer.
Pre-cat lacquer is popularly used to finish bathroom and kitchen cabinets, due to its nonporosity and smooth, wipeable surface. It is a common ingredient in automotive paint. It has a rich glow and can stand up fairly well to knocks and scrapes, though it isn’t as durable as polyurethane.
To avoid premature hardening, post-catalyzed lacquer is also available for people who don’t mind doing a little unsupervised chemistry. This product is sold in two separate containers, which are mixed by the purchaser immediately before application.
Since the catalyst has not yet been added to the lacquer mixture, it does not begin to cure. The result is a longer shelf-life for post-catalyzed lacquer than the pre-cat version.
What Is Polyurethane?
Polyurethane is perhaps the best-known of all the liquid wood finishes. This easy to apply all-rounder provides wood with excellent protection from denting, scuffing, scraping, pests, moisture, fungus, and mildew.
Technically a type of varnish, polyurethane is a synthetic formulation that can be oil or water-based. Oil-based polyurethane contains 45-50% solids and requires fewer coats to achieve the same finish that a water-based would.
Water-based polyurethane has a very similar cousin called polycrylic. It contains 30-35% solids and dries to a ‘water-white’ clear finish. It is very simple to apply to wood pieces.
A few other distinctions between the different types of polyurethane:
- Water polyurethane emits lower levels of VOCs and dries more quickly than oil-based versions. If applied in thick layers, it tends to look plasticy.
- Oil-based polyurethane takes longer to dry and cure and can have a pungent aroma, but it looks more natural when cured and will do a slightly better job of protecting the wood from damage.
Sprayable, brushable, and wipeable versions of polyurethane are readily available. This versatile finish is often used as a top coat over paint, stain, or other wood finishes due to its virtual indestructibility.
As a curing finish, polyurethane hardens in two phases. The first happens as the moisture in the finish evaporates, leaving the surface dry to the touch. The next phase, called ‘curing’, occurs over about 30 days as a molecular reaction takes place between the oxygen in the air and the contents of the polyurethane.
Pre-Catalyzed Lacquer vs Polyurethane
To decide which finish is right for your next project, here are the similarities and differences between pre-catalyzed lacquer and polyurethane.
On the surface, these two liquid wood finishers appear quite similar.
Polyurethane and pre-catalyzed lacquer both protect wood from the same dangers: water, pests, fungal growth, and regular wear and tear.
Polyurethane will provide a better protection over the long run, but both pre-cat and poly provide good protection.
Unlike penetrating finishes that soak into the pores of the wood, polyurethane and pre-catalyzed lacquer form a durable film on the wood’s surface.
Lacquer and polyurethane can be either clear or tinted. Tint is achieved with dyes or pigments. One of the differences between dye and pigment is opacity. Pigments are large particles that reflect light, which makes them opaque. They adhere to the surface of the wood through the use of a binder.
Dyes are smaller particles and do not reflect light. Lacquer or polyurethane tinted with dye is transparent or semi-transparent.
Mechanism of Action
Polyurethane and pre-catalyzed lacquer harden in two phases. First, they dry. Then, they cure.
While these two finishes appear similar on the surface, they have many differences in appearance and performance.
The colors that can be achieved with pre-cat are much more vibrant than tinted or pigmented polyurethane.
High-gloss versions of polyurethane are available, and it can be buffed or burnished after application to increase the reflectivity.
However, nothing can match the ultra-reflective and shiny finish that lacquers, including pre-catalyzed lacquers, are known for.
The time you have to work with pre-catalyzed lacquer is very short. As the spray droplets are hitting the wood, the drying process is already beginning, and pre-cat lacquer dries within 30 minutes.
Polyurethane dries in six to eight hours or 24 hours, depending on the formulation.
A smooth, clear coat of polyurethane can easily be achieved with nothing more than a brush. Brushing lacquer is much more difficult and is generally not recommended as a project for amateurs.
Number of Coats
Pre-catalyzed lacquer requires a lot more coats than polyurethane. It is rare to apply more than two or three coats of polyurethane. As many as ten coats of pre-catalyzed lacquer may be required.
Although pre-catalyzed lacquer provides more impact resistance than other lacquers, it cannot match the exceptional durability of polyurethane.
In particular, polyurethane is more durable against water and moisture than pre-cat lacquer.
Major Differentiating Factor
Both polyurethane and pre-catalyzed lacquer can be used to achieve a durable, clear film finish on top of wood. While polyurethane is more durable than pre-catalyzed lacquer, that’s not the biggest differentiator between the two.
Polyurethane is much, much easier to apply than lacquer due to it’s longer dry time and superior brushability.
If you already have a professional-grade sprayer and are comfortable using it, applying lacquer might be easier because of the quick dry time between coats.
But for the rest of us, faced with the choice between an expensive machine rental or a brush and a can of poly, the decision is easy – pick polyurethane over pre-cat lacquer.
When to Use Pre-Catalyzed Lacquer
Use pre-catalyzed lacquer to finish interior cabinetry, or better yet, hire a professional to do it for you.
Maintaining the appropriate ratio of thinner, retardant, and pigment to achieve the results you’re looking for takes significant experience. Experience is only gained through making mistakes. If you have the time and the desire to get very good at spraying on lacquer, it would make sense to start with non-catalyzed lacquer first to keep things simple.
When to Use Polyurethane
Use polyurethane to protect wooden floors, work surfaces, and interior furniture that will be exposed to high-traffic.
The durability of oil-based polyurethane is impossible to beat, and water polyurethane isn’t far behind.
Which Is Better, Pre-Catalyzed Lacquer or Polyurethane?
Polyurethane is better at protecting wood.
Pre-catalyzed lacquer is better at providing vibrant colors and the shiniest gloss finish.