Yes, it is possible to paint over unfinished oil-based stained Alder wood, but it requires proper preparation to ensure the best results. Here is a step-by-step guide on how to successfully paint over unfinished oil-based stained Alder wood:

1. **Prepare the Surface:**
– Sand the wood surface lightly with medium-grit sandpaper to smooth out any rough areas or imperfections.
– Clean the surface thoroughly to remove any dust, dirt, or debris.

2. **Prime the Surface:**
– Apply a high-quality bonding primer that is suitable for both oil-based stains and latex paint. This will help the paint adhere better to the wood surface.

3. **Choose the Right Paint:**
– Select a high-quality latex paint that is specifically formulated for wood surfaces. Make sure the paint is compatible with the primer you have used.

4. **Apply the Paint:**
– Use a high-quality brush or roller to apply an even coat of paint onto the prepared surface. Allow the first coat to dry completely before applying a second coat, if necessary.

Real bummer as Alder can be a gorgeous wood.