Why do adhesion problems occur with water-based varnishes?

Adhesion problems on wooden floors often arise due to improper surface preparation or unsuitable environmental conditions. Water-based varnishes have specific characteristics that require careful preparation and application to adhere properly. If the floor is not properly sanded, or if there is dust, oil, or other contaminants, the varnish may not adhere evenly to the surface. Moisture is another common issue, as wood is sensitive to humidity, and if the air humidity is too high during varnishing, it can negatively affect the varnish's adhesion. The choice of sandpaper is also important: using sandpaper that is too coarse can leave a rough texture, reducing the varnish's ability to adhere. Temperature also plays a critical role. Water-based varnishes need a minimum processing and drying temperature, usually above 13°C, to cure properly. If the temperature is too low, the varnish layer may not dry sufficiently, leading to adhesion problems. It’s also essential to allow each varnish layer to dry properly before applying the next, as trapped moisture can cause adhesion issues.

Bona Classic reduces the risk of edge bonding on wooden floors thanks to its high filling power and acrylic dispersion.

To prevent adhesion problems when varnishing wooden floors, using a product like Bona Classic can be a solution. Bona Classic is a one-component water-based acrylic primer designed to be used with Bona's water-based topcoats. One of the major advantages of Bona Classic is that it reduces the risk of edge bonding, a common problem on wooden floors, especially on end grain or floors with underfloor heating. This is due to the product's high filling power, which gives the floor a well-filled surface without the planks bonding at the edges. The acrylic dispersion in Bona Classic ensures an even distribution and adhesion of the varnish across the entire surface. Additionally, the product has a high solid content, meaning it contains less solvent and provides a covering layer faster. This makes it easier to achieve an even result without the need for extra layers. However, it’s crucial to prepare the floor properly by sanding it down and removing all sanding dust and other contaminants so Bona Classic can adhere optimally. The varnish should also be applied at the correct temperature and humidity levels, as recommended by the manufacturer.