Polyisocyanate is commonly used as a cross-linking agent in two-component polyurethane (PU) wood finishes. These finishes provide excellent protection, durability, and appearance to wood surfaces. Here's how to use polyisocyanate in wood paint:

1. Prepare the surface: Clean the surface of the wood and sand it until it's smooth and free of debris. Make sure to remove any oils, waxes, or previous coatings from the surface.

2. Mix the components: Polyisocyanate is typically used in conjunction with a polyol resin. The two components are mixed together in the desired proportions. Some PU finishes use a mixing ratio of 1:1, while others use a ratio of 2:1. Make sure to read the product specifications for the specific polyisocyanate product you're using.

3. Apply the finish: Using a brush, roller, or spray equipment, apply the mixed PU finish to the wood surface in thin, even coats. Follow the manufacturer's instructions for the recommended number of coats and drying times between coats.

4. Cure the finish: Once the final coat is applied, allow the finish to cure fully before exposing the wood surface to moisture or heat. The curing time will vary depending on the specific PU finish being used and the conditions in which it's applied.

It's important to follow the manufacturer's instructions and safety precautions when using polyisocyanate and PU finishes. This includes wearing protective clothing, such as gloves and a respirator, and working in a well-ventilated area.