A clear understanding of use cases is perhaps the most valuable skill when it comes to selecting the right type of finishing solution to use on your wood project. Naturally, not all finishes are created equal—they all have their time, place, and use case.
The Basics: Conversion Varnish (CV)
Many commercial and industrial projects call for the use of conversion varnish (CV), and it may be the best finish option for your next project too, depending on the circumstances. Today we’ll discuss the specifics of conversion varnish, including how to determine use case, how it compares to other finishing products, and a few general application tips.
CV is perhaps the longest-lasting and most durable finishing solution, which is why it’s used by professionals for commercial and high-production purposes. This industrial-grade product is most often applied with a sprayer by an experienced user.
Examples of common projects that are finished with conversion varnish include:
- Kitchen cabinetry
- Fine furniture
- Architectural millwork
- Store fixtures and displays
Similarities Between Finishes
All of the finishing solutions discussed below are high-performance coating solutions. Synthetic sealants like conversion varnish, lacquer, and polyurethane are applied with the intention of protecting the wood surface from heat, moisture, fading, and wear-and-tear. They’re all available in various sheens (i.e. matte, gloss, semi-gloss), and many manufacturers will offer a variety of colors and shades for achieving a specific look.
Comparing Coatings: Conversion Varnish vs. Lacquer
CV can be compared to lacquer in a handful of ways. Two primary categories of lacquer exist: catalyzed and pre-catalyzed lacquers.
The Basics: Pre-Catalyzed and Catalyzed Lacquers
Both types of lacquers contain nitrocellulose resin, which makes them similar to acrylic when dry. Their name similarity is due to the fact that the chemical composition of the final solution is virtually identical. The difference between a catalyzed and a pre-catalyzed lacquer is simply whether the hardening agent, or acid catalyst, is already present in the solution prior to opening.
- Pre-Catalyzed Lacquer (Pre-Cat): As the name suggests, these solutions are already catalyzed by the manufacturer before being packaged. Although this single-component system tends to give pre-cats a shorter shelf life, it also allows for the product to be used straight off the shelf without the need for any additives prior to application.
- Catalyzed Lacquer (Post-Cat): This two-component system doesn’t yet contain the acid catalyst that initiates the chemical curing process. This normally gives the product a longer shelf life. Its pot life, on the other hand, is shorter than that of a pre-cat because it must be utilized shortly after adding the catalyst to ensure the best results.
CV is similar to post-catalyzed lacquer in that conversion varnish also requires the addition of an acid catalyst prior to application. However, lacquers contain nitrocellulose, unlike conversion varnishes which employ a different resin system (most commonly, alkyd amino.) Nitrocellulose-based finishes are more prone to yellowing and generally offer less longevity than conversion varnish.
Differences in Application
Lacquers are very versatile and can be applied with a brush or a sprayer, depending on what type of coverage you’re looking for. Using a sprayer will cover more area faster, but using a brush offers a bit more control and produces a thicker coat. Note that some lacquers will require the addition of a thinner before spraying to get the consistency just right.
Comparing Coatings: Conversion Varnish vs. Polyurethane
Polyurethane is another single-element topcoat widely used in wood finishing. But because it’s made with different resins, it offers a bit less flexibility and more rigidness than CV.
The Basics: Polyurethane
Another type of synthetic sealant, polyurethane is a sticky, transparent solution applied over surfaces as a topcoat to protect the wood and add shine. The two primary types of polyurethane are oil-based and water-based. Water-based polyurethanes tend to dry faster and tend to have less of an odor. Oil-based polyurethanes typically take longer to dry, but are considered slightly more durable than their water-based counterparts. Oil-based polyurethanes may also result in yellowing of the wood surface over time.
Differences in Application
Polyurethane is a thick, highly viscous substance that soaks deep into the grain, penetrating the wood, which is why it’s usually applied using a bristle brush. Catalyzed lacquer and conversion varnish are both considerably less viscous, enabling them to be applied with a sprayer.
Comparing Coatings: Other Finishes
Conversion varnish, lacquer, and polyurethane aren’t your only options when it comes to coating solutions, so we address a few other common finishes below:
Shellac vs. CV
Shellac is widely considered to be the least durable of the finishing options mentioned and typically isn’t used as a final topcoat. Made from beetle excretions, shellac is biodegradable—it is naturally occurring, non-toxic, easier to clean up, and easier to repair than its industrial coating counterparts. Although shellac is a common component of many commercial lacquers, lacquers are composed of resin mixed with a solvent agent. Conversion varnish contains no shellac, and is typically made from natural oils.
Varnish vs. Conversion Varnish
Simple varnish, or spar varnish, is an off-the-shelf finishing solution sold already containing the hardening agent. Typically applied using a bristle or foam brush, it can be compared to polyurethane in terms of consistency and is commonly used in the marine industry. Spray conversion varnish, which we discuss primarily in this article, is certainly the more robust and time-saving option, hence its employment by professionals for commercial use.
Additional Conversion Varnish Application Tips
As with any coating solution, CV should be applied according to the manufacturer’s instructions on the packaging. Additionally, conversion varnish shouldn’t be applied directly to raw, untreated wood without adequate preparation. The surface, at the very least, must be sanded or otherwise pretreated to achieve the best results. Sanding and proper dusting between coats is essential as well.
A few other useful pieces of advice for using CV according to a WOODWEB forum include:
- Depending on the equipment you’re using, you may need to employ a high-quality thinner or xylene to control drying time and optimize product consistency.
- Proper shop temperature is critical, as varnish cures best at room temperature (approximately 70 degrees Fahrenheit).
- Always utilize a respirator or face mask when applying conversion varnish and any other necessary personal protective equipment (PPE).
Finding the Perfect Finish for Your Project
Our job at FinishWorks is to equip you with the expert knowledge and premium products necessary to make the most educated decision on which coating will give you your desired results. Whether that’s a superior CV or a different coating that’s better suited to your experience and project requirements, we’re committed to finding you the ideal solution for your needs.
The quality of your finishing solution has a significant impact on the final appearance and integrity of your project. The durability and aesthetics of the end result are reliant on the use of the proper finishing product and application technique. Ensure you know what solution you need—and if you don’t, consult with the experts at FinishWorks to find the perfect finish for every project, every time.
