If you're experiencing issues with PVA waterproof glue not holding oak joints well in your outdoor woodworking projects, there are a few factors to consider and alternative glues to explore. Oak is a dense and oily wood, which can make it challenging for some glues to form strong bonds.
Here are some considerations and alternative glues that might work better for outdoor use with oak:
Epoxy Resin: Epoxy is a popular choice for bonding oak and other hardwoods. It creates a very strong and durable bond, and it is highly resistant to water and weathering. Epoxy typically comes in two parts that need to be mixed together before use, ensuring a strong and reliable adhesive.
Polyurethane Glue: Polyurethane glues, commonly known as "PU glue" or "Gorilla Glue," are also excellent for outdoor applications and can bond well with oak. They expand as they cure, filling gaps and creating a strong, waterproof bond. However, keep in mind that polyurethane glue foams up while curing, so use it sparingly and clean up any excess promptly.
Marine-grade Adhesives: Look for adhesives specifically labeled as "marine-grade" or "exterior-grade." These are designed to withstand harsh outdoor conditions, including moisture, UV exposure, and temperature changes.
Preparation: The success of any glue joint depends on proper preparation. Make sure the surfaces to be glued are clean, dry, and free from any oils, dust, or debris. Sanding the surfaces lightly can also help improve the adhesive's grip.
Clamping Pressure: Regardless of the glue you choose, applying adequate clamping pressure during the curing process is crucial for achieving strong bonds. Follow the manufacturer's recommendations regarding clamping time and pressure.
Wood Moisture Content: The moisture content of the wood can affect the adhesive's performance. Ideally, the wood should have an equilibrium moisture content (EMC) that matches the expected conditions of your project's location. If the wood is too wet or too dry, it can impact the bond.
Temperature and Humidity: Both the temperature and humidity can influence the curing process of adhesives. Follow the recommended temperature range provided by the adhesive manufacturer for the best results.
Remember that while certain glues are more suitable for outdoor use and oak, no adhesive is entirely foolproof. Wood movement due to changes in humidity and temperature is inevitable, and this can affect glue joints over time. Employing good woodworking techniques, such as appropriate joinery and allowing for wood movement, can also contribute to the longevity of your outdoor woodworking projects.
If you continue to encounter issues, you might want to experiment with a few different glues to see which one works best for your specific application and local environmental conditions. Additionally, consulting with experienced woodworkers or professionals at your local woodworking store can provide valuable insights and recommendations.