- I’ve had good results using Minwax Helmsman exterior urethane on interior wooden window surfaces:
- it’s easy to use,
- dries virtually clear,
- and forms a tough film yet creates a smooth finish.
- Remember to sand the wood lightly with 240-grit sandpaper or a fine 3M rubbing pad after the first coat has dried.
- Sikkens Cetol works very well on windows, but all versions are some shade of golden or brown colour.
- Also – and this is important – I’d wait until warm weather in the spring before finishing your windows. Even though your room might be cozy during winter, the wood of the window is quite likely to be too cool for any finish to dry properly.
When it warms up enough for finishing, you’ll get best results if you sand back to bare wood first. A detail sander is the perfect tool to use. As a final step, use a razor blade scraper to remove any finish that got on the glass.