Water-Based Finishing Systems for Wood: Advantages and Disadvantages

A water-based finishing system is a wood finishing system that uses water-based finishing materials. This system uses water-based stains, water-based coatings, glazes, and other water-based finishing materials. This system is gaining popularity because it is considered more environmentally friendly than conventional finishing systems that use solvent-based materials. Water-based is also considered the finishing solution for the world's future, which desires a clean and healthy environment.

Advantages of a Water-Based Finishing System

• Environmentally friendly

Unlike solvent-based systems, which always emit solvent vapors, water-based coatings produce much lower solvent emissions. While water-based systems still use solvents, they are released into the environment at very low levels. Therefore, the solvent produced by a water-based finishing system can be considered non-existent. This makes the finishing room and its environment safer and healthier. This makes it an ideal choice for the modern furniture industry, especially in developed countries that require strict health standards.

• Safer, less risk of fire 

One of the biggest dangers in the wood finishing industry is the risk of fire. Solvents, thinners, and solvent-based finishing materials are flammable. Even the smallest spark that comes into contact with a finishing material can quickly spread into a devastating fire. Furthermore, the wood industry is home to many dry wood products, which are also highly flammable. The combination of solvent-based finishing and dry wood creates a very high fire hazard.

Water-based finishing systems that use water-based thinners are much safer than solvent-based finishing. Water, the main component of finishing materials, is non-flammable. The use of water-based finishing significantly reduces the risk of fire in the finishing room to a minimal level.

• Wide choices for colors and appearances

Finishing material technology is now very advanced, with numerous innovations developed to meet the demands of the wood industry. Water-based finishing materials are widely available and can be used relatively easily with increasing quality. Many types of water-based finishing materials are available to meet the needs of the wood industry in terms of color, appearance, strength, and performance.

• Easy in application

Most water-based finishes are designed to be as easy to apply as solvent-based materials. These materials dry quickly, are easy to use, and are readily available on the market. This makes it even easier for the woodworker and wood finisher to use these finishes.

antique brown oak finish

Disadvantages of Water-based Finishes

• Sensitive to environmental conditions

Water-based finishing materials use water as a thinner, so the drying process occurs through its water evaporation. This water evaporation process is highly dependent on room conditions, especially temperature and humidity. When the air humidity and temperature are in ideal conditions, the coating can dry quickly and easily. However, when conditions are less than ideal, the drying process can be disrupted, resulting in a difficult and lengthy drying process. Less than ideal room conditions can even affect the quality of the film layer and the color of the finish. Therefore, it is highly recommended to equip the finishing room with an adequate oven to control the temperature and humidity.

Ideal room conditions can vary depending on the type of coating used, but generally, the ideal temperature is around 25°C to 35°C, and humidity is between 60% and 80%. If the temperature is too cold or hot, or if the humidity is too high or too low, the coating drying process can be disrupted.

• Wood grain raising

Water naturally moistens the wood surface and causes the grain to rise more than solvents. Therefore, water-based coatings tend to roughen the wood surface due to the raised grain. Therefore, water-based coatings require more precise sanding, both in preparation for the unfinished wood and when sanding the coats during the finishing process.

• Imperfect of inter-coating layers bonding

Water-based finishing cannot dissolve the coating layer beneath it; therefore, this coating requires a slightly different application method. Spray applications cannot be too wet; excessively wet spray can cause the coating to melt and sag on the surface. Besides the spray method, the sanding process is crucial. Sanding is necessary not only to create a smooth and even surface but also to create the scratches needed to strengthen the bond between the coating layers. Therefore, sanding water-based coating layers must be done properly, ensuring the entire surface is sanded using the correct grade of sandpaper. Mistakes in the sanding process not only result in an imperfect appearance but can also affect the strength and adhesion of the finishing layer.

• Tendency to have a cloudy appearance

Water-based coatings will have a slightly different appearance than solvent-based ones. In general, water-based coatings tend to produce a slightly cloudy appearance. The thicker the coating film layer, the cloudier it appears. Therefore, a water-based system is not particularly suitable for finishing with thick films and transparent colors. Solid-color finishes with high film may still be achieved with water-based coatings, but with careful consideration of the drying and sanding processes, which require time and precise detail.

Water-based Finishing Process

•  Wood Filler 

Wood filler is a material that fills the pores and grain of wood. This wood filler is necessary if you want a finish with closed pores. Wood filler is applied evenly to the wood surface using a brush, roller, rag, or scraper, depending on the type of wood filler used. Ensure the wood filler fills all pores and grain evenly, as incompletely filled pores and grain can lead to problems in subsequent finishing processes, such as open pores and grain, bubbles, and pinholes, which are very difficult to repair in subsequent finishing processes.

Sand thoroughly to remove any filler adhering to the surface. Ensure the filler remains only within the pores and grain of the wood and does not remain on the surface. Filler remaining on the wood surface will affect the appearance of the finish and its adhesion.

• Stain 

Stain is a material that colors wood. This stain is needed if you want a finishing color that differs from the wood's natural color. Stain is not necessary if the desired finishing color is the wood's natural color. There are two types of stain: woodstain (stain for transparent colors) and stain for solid colors, as well as base coat, primer, and enamel. Stain can be applied by spray, brush, or roller, depending on the type of stain used. Ensure the stain is applied correctly according to the desired color and is dry before continuing.

• Sanding Sealer 

Sanding sealer is a material that forms a film layer and produces a smooth surface when finished. This sanding sealer also serves to protect the stain, glaze, and filler applied underneath. There are several types of water-based sealers that will determine the appearance and strength of the finishing layer. Sanding sealer is generally applied by spray, although other application methods such as brush, roller, curtain coater, etc. are also possible.

Apply the sanding sealer evenly to the surface, wait for it to dry, and then sand thoroughly before continuing with the next process.

•  Glaze

Glaze is a stain applied between clear coats. For more details, please see our previous article, Glaze for Wood Finishing.

Water-based glaze is widely available, as is solvent-based glaze. Apply the water-based glaze according to the desired color and appearance. Ensure the glaze is dry before applying a sealer or top coat.

• Top coat

A top coat is a finishing material that provides protection for the finish underneath and also creates a gloss. Water-based topcoats are generally applied over a finely sanded sealer. Thoroughly prepare the surface before applying the top coat. The sealer layer must be thick enough and thoroughly sanded to create a smooth, even surface. Apply the topcoat thoroughly and allow it to dry completely to create an even, smooth, and strong film. Avoid applying a top coat that is too thick, as it tends to produce a cloudy appearance. One or two top coat applications should be sufficient if the underlying surface has been properly prepared.

Tips for applying a water-based finishing system

The application of a water-based coating system is essentially the same as that of a solvent-based one. However, it's important to understand that water-based finishing materials have slightly different characteristics. Therefore, it requires slightly different application techniques. Here are some things to consider for successful water-based finishing applications.

• Use good-quality material

Material quality is a crucial factor in determining the quality of the finishing result, as using good materials is crucial for producing good results. Choose high-quality material and the right type according to the needs and strength of the desired finishing layer. There are several types of water-based finishes designed for various finishing applications, such as indoor water-based, outdoor water-based, heat-resistant water-based, solvent-based, etc. Choose the right finishing materials according to the desired finishing quality specifications.

• Correct application process

Proper application is required to produce a finish with the desired quality, color, and appearance. Make sure you create a step panel to achieve the desired color and appearance, and then follow each step in the step panel. Pay attention to application techniques, such as spraying method (application), drying time, sanding process, mixing method, etc., correctly.

• Wood preparation

Finishing layers should not be used to address problems with the unfinished product. To produce a high-quality product, proper preparation of the raw material must begin. Ensure the raw wood product is dry according to the required MC standards. Wet wood will complicate the drying process of the finishing layer, especially since water-based materials use water as a thinner. Wet wood will also invite many problems, such as coating that doesn't dry properly, cloudy colors, mold on the surface, and even construction issues like splitting, warping, etc.

Ensure the surface is smooth, clean, and tidy, free of scratches, dirt, dents, and other untidy problems that will degrade the quality of the finish.

• Oven for the finishing room

The drying process for water-based material occurs due to the evaporation of water from the coating layer into the surrunding air. This drying process is easily disrupted in humid and cold conditions; therefore, it is highly recommended to equip the finishing room with an oven. An oven is a tool that functions to control the conditions in the finishing room. In hot and dry conditions, the drying process can proceed smoothly, but in cold or humid conditions, an oven is needed to control and maintain the ideal temperature and conditions for the material drying.