Fungal Problems in MDF Products

Medium Density Fiberboard (MDF) is widely used in the woodworking industry. It is commonly applied in the production of panels, boards, and other flat products as a replacement for solid wood. As an engineered wood product, MDF offers many advantages over solid wood. It is more uniform, more stable, and more cost-effective than natural wooden planks. As discussed in our previous article, MDF for Furniture, these benefits make MDF a popular material choice.

However, despite its advantages, MDF also has several disadvantages. One of the most significant issues is its high susceptibility to fungal and mold growth.

What Is MDF and Why Is It Vulnerable?

MDF is an engineered wood product made from wood fibers, wax, and resin. These materials are heated, mixed evenly, and then molded under pressure to form boards of various thicknesses. A melamine resin layer is commonly applied to the surface of MDF to create a smooth finish and provide surface protection. While melamine resin improves durability, it also releases formaldehyde gas, which is considered harmful to human health. Since the early 2000s, many countries have imposed strict regulations limiting formaldehyde emissions. As a result, MDF manufacturers have been forced to reformulate their production processes to reduce formaldehyde content.

These changes, however, have also reduced some of the protective properties of MDF. Consequently, fungal and mold problems are now reported more frequently than before the 2000s.

Common Areas Affected by Mold and Fungi

Mold growth on MDF products is most commonly found on unfinished or lightly coated surfaces, especially in hidden or unexposed areas such as : back panels of furniture, undersides of tabletops, side panels, inside drawers, etc.

Meanwhile, MDF surfaces that are well finished—such as those covered with veneer, vinyl, decorative paper, or thick film coatings—are much less susceptible to fungal attacks.

Although fungi may develop in unexposed areas, their presence still significantly degrades product quality. Mold damages the appearance of the furniture and creates an unpleasant visual impression. More importantly, fungi can release airborne spores that spread throughout a room, potentially causing health issues.

 The fungi at the naked M.D.F.

How to  Treat Fungal Attacks on MDF

•  Clean Fungal Growth Immediately

If fungal growth is detected, it should be removed as soon as possible. Use a cloth dampened with paint thinner or a suitable cleaning solution to wipe and scrub the affected surface until all fungi are removed. Be careful to ensure the cleaning liquid does not damage or dissolve the existing finish.

After cleaning, allow the surface to dry completely. Lightly scuff sand the area, then apply a new coating layer. Adding anti-fungal additives to the coating can further reduce the risk of future fungal growth. Ensure the coating is thick enough to provide sufficient protection while still maintaining the desired appearance.

•  Keep MDF Products Dry

Moisture and humidity are the primary factors that promote fungal growth. Damp surfaces provide an ideal environment for mold to develop. To prevent this, MDF products should always be kept dry.

Store MDF materials in air-conditioned or warm rooms, maintaining a moisture content below 10%. Good air circulation is essential to keep the environment fresh and dry.

• Apply Proper Surface Coatings

MDF is a hygroscopic material, meaning it absorbs moisture from the surrounding air. Uncoated or exposed MDF surfaces will readily adjust their moisture content to match environmental humidity levels.

Applying paint or coating seals the surface and reduces moisture absorption. Make sure you apply enough layer of coating to cover and coat the MDF surface. Catalyzed coatings, such as polyurethane (PU) or acid-catalyzed (AC) coatings, provide better protection than single-component finishes like nitrocellulose (NC) or water-based coatings. If necessary, additional anti-fungal additives can be included in the coating for extra protection.

Water-based coatings must be applied with caution. The water content in these coatings can increase the moisture level of MDF and encourage fungal growth if not dried properly. Application should be done on hot, dry days whenever possible. In cold or humid conditions, an oven or controlled drying system is strongly recommended to ensure proper curing.