What is wood coating?
Wood coating refers to the process of applying a protective layer or finish to wood surfaces to enhance their appearance, durability, and resistance to damage from moisture, heat, UV radiation, and other environmental factors.
These coatings can be either clear or pigmented and are most commonly applied by roller and curtain coating or spraying. Wood coatings can be made from a variety of materials, including oils, varnishes, lacquers, stains, and paints, each offering different benefits and levels of protection. The choice of coating depends on the intended use of the wood surface and the desired aesthetic outcome.
In the furniture industry, the most common high performance finish is a UV curable polymer coating applied on a roller coater / spraying line. In a common sequence, wooden substrates are sanded, sealed with UV cured filler and sanded again before a sequence of base coats and top coats are applied. All of these coatings are UV cured with varying combinations of UV LED or mercury vapour lamps.
UV wood coating applications:
- Furniture and cabinet coatings: UV curing systems are commonly used to cure clear and pigmented coatings on furniture and cabinets.
- Flooring coatings: UV curing is used in the production of wood flooring to cure the finish coats.
- Exterior wood coatings: UV curing systems are increasingly used in the production of exterior wood coatings, such as stains and varnishes.
- Joinery coatings: UV curing is used in the production of joinery products, such as windows, doors, and moldings.
- Sealing and priming: UV-curable sealers and primers can be used to prepare the surface of wood for further coating applications. They provide excellent adhesion, hardness, and scratch resistance.
- Staining: UV-curable stains can be applied to wood to provide colour without the need for traditional drying time.
- Topcoats: UV-curable topcoats can provide a high level of gloss, clarity, and durability, making them an attractive option for furniture and other high-end wood products.
How are UV & UV LED used in wood coating?
Mercury vapour lamps and UV LEDs are the most common drying technology used in wood coating applications. The UV light initiates a chemical reaction that quickly hardens (polymerises) the coating (usually an acrylate based resin). You can find further specific information on the UV curing process and UV curing science on our website. This technique can significantly reduce the curing time, increase the production speed, and improve the overall performance of the coating by increasing its resistance to wear, scratches or chemical damage.
UV LED, an increasingly popular curing option, offers the better process efficiency and energy savings compared to traditional mercury vapour lamp UV curing techniques: UV LED lights emit a longer and narrower UVA wavelength of light compared to mercury technology, which is ideal for penetrating deeper into thick coatings and promoting better adhesion to the base wood layer or cohesion between base coats. It also maintains a softer gelled surface ideal for additional coating layers to be applied on top.
In addition, LED diodes consume considerably less electricity than mercury lamps with energy savings in excess of 70% frequently possible. The associated reduction in carbon footprint along with the elimination of mercury for its environmental concerns are the primary drivers of a transition to LED curing in this market.
Traditional mercury reactive UV coatings are typically not compatible with UV LED so new coatings must be sourced to run LED on a line. In addition, top coats are typically not fully developed for LED curing presently and so a combination of LED for sealers and base coats, with mercury lamps for top coats, is a common configuration.
Typical coating line configurations
Depending on the specific application and available coatings, GEW can advise the best setup of curing technology for each unit on a coating line.
The diagrams below illustrate a typical mercury vapour lamp configured coating line and a more energy efficient hybrid line configured with UV LED where possible and mercury vapour technology where still required.
Benefits of UV for wood coating
- Faster curing times: UV curing is a fast process that can cure wood coatings in seconds or minutes, compared to traditional curing methods that can take hours or even days. This allows for faster production and turnaround times, increasing efficiency and productivity.
- Increased productivity: Because UV curing is a dry process, there is no need for solvents or other wet chemicals, which can slow down production times. This leads to increased productivity and a more streamlined production process.
- Enhanced durability: UV-cured wood coatings are known for their exceptional hardness, abrasion resistance, and chemical resistance. This provides excellent protection for wood surfaces, making them more durable and longer-lasting.
- Improved appearance: UV-cured wood coatings provide a high-gloss finish that is clear and consistent, giving wood surfaces a more polished and attractive appearance.
- Environmental friendliness: UV curing is a more environmentally friendly option compared to traditional curing methods that use solvents and emit harmful VOCs. UV curing produces fewer emissions and has a smaller environmental impact, making it a greener option for wood coatings.
- Reduced lead times due to quicker finishing processes.
Further benefits of UV LED
- Energy savings: Changing from mercury UV lamps to LED even only on some coating units can reduce the number of curing lamps being used and saves significant amounts of electricity. For example, upgrading two UV filler stations and four UV base coat stations to LED curing on a typical production line can save up to €200,000 per year in energy and consumable parts costs.
- Better cohesion between base coats: Longer wavelength LED light penetrates deeper into coatings and activates curing at the joint between coating layers which can improve cohesion between base coats. In addition, the gelled surface from LED is slightly softer which ensures better cohesion to the next coating layer. Both mechanisms work in tandem.
- Better compatibility with resinous woods and veneers: UV LED technology generates less heat than mercury arc UV, making it a better option for coating temperature-sensitive woods where resins may leach at high temperature and cause issues with sanding.
- Instant on/off: UV LED lamps can be turned on and off instantly, which eliminates the need for warm-up time and reduces energy consumption during breaks or downtime.
- Better control over curing process: UV LED diodes degrade consistently over time when compared to mercury lamps which vary significantly over short periods as lamps degrade and reflectors become dirty, allowing for greater precision and consistency in the coating application.
GEW products for wood coating
GEW has both UV LED and mercury arc solutions for wood coating applications. Read on for further information:
LeoLED2
LeoLED2 takes LED performance to new heights over GEW’s already highly-acclaimed, water-cooled LeoLED system. Offering a 55% increase in electrical power (140W / cm), a 50% increase in UV dose (300mJ / cm²) and a 45% increase in UV irradiance (44W / cm²) compared to its predecessor, LeoLED2 is GEW’s next generation UV LED curing system that guarantees the best performance on the market for the most challenging curing applications.
As with the generation 1 model, LeoLED2 is available in both a cassette version and a compact version, depending on the requirements of the customer, their equipment and their application. Both models are designed to interchange with every current arc lamp model in GEW’s range. This patented ArcLED technology gives ultimate flexibility on press, no matter the application.
Like all our UV products, LeoLED2 is powered by GEW’s RHINO power supply for ultimate reliability and controlled by RHINO Control which comes as standard with IoT remote monitoring. This allows our customers the flexibility to go ArcLED without having to invest in a whole new, independent system. For customers with a GEW arc system installed, an upgrade can be as simple as adding a chiller, a UV LED lamphead, and running an upgrade.
LeoLED2 also comes in two power level options, offering ultimate customisability to customers, depending on their application and energy saving needs, whilst providing faster printing speeds alongside GEW’s renowned process reliability.
E4C
E4C offers the highest power available from the GEW range, to support the most demanding UV curing applications and the fastest speeds. It performs to the harshest cure test procedures.
E4C has optically tuned reflectors to maximise curing power and operates quietly, with minimal air requirements. Water flow monitoring technology ensures water flow at all times, and the E4C’s water-cooled reflectors support the highest UV power whilst limiting heat transfer to the substrate, making it safe for a broad range of heat-sensitive materials.
It is designed to operate with the lowest level of maintenance and is engineered for fast, easy lamp changes. All replaceable components are plug-and-play, and the reflectors can be cleaned and fully replaced without breaking the water seals. Furthermore, the reflector mechanisms and seals are tested to millions of operations to ensure reliability.
Like all our UV products, E4C is powered by GEW’s RHINO power supply for ultimate reliability and controlled by RHINO Control which comes as standard with IoT remote monitoring. This allows our customers the flexibility to use arc and LED technologies side by side on a press.
Find out more below, or download our brochure now:
ArcLED compatibility
LeoLED2 and E4C are both ArcLED compatible.
ArcLED’s power system allows you to switch seamlessly between mercury arc and LED technologies. Both arc and LED cassettes are compatible with the same power supply and fit in the same housing for ease of change.
To find out more, download our brochure below:
Products for wood laminating
ExciRay
GEW’s ExciRay lamp systems utilise dielectric barrier discharge (DBD) lamps to produce quasi-monochromatic vacuum ultraviolet radiation, typically at 172nm. This radiation is commonly used for mattification of surface coatings and in the wood industry is most commonly used in the production of matt effect laminates for cabinets or flooring.
GEW ExciRay lamps can be produced up to 255cm and can be custom integrated for your specific application including provision for all required nitrogen inerting and control. They are also seamlessly integrated into the wider GEW UV systems which may be required for gelling or post-cure so that GEW can provide a turnkey curing/cleaning solution for your process. Our experienced engineers also ensure rigorous adherence to international safety standards.
Speak directly to our sales team
If you would like to know more, or discuss your requirements, we are here to help. Please contact the sales representative that is best placed for your region.
Region, International:
Justas Žvikas
Sales Representative, Wood Coating
Email Justas directly
