The recommended procedure for painting a patio door is as follows. Proper preparation of the wood is key. For more about painting see How to Paint Interior Doors.
1Hang your doors unfinished for two to three days and then remove them from the hinges. This will allow the wood to adjust to the temperature and humidity levels of that location.
2Thoroughly clean the door surfaces, clearing off any dust or debris. Note any slight imperfections or blemishes. Sand with 120-grit sandpaper to smooth these problem areas. Always sand with the grain to avoid cross-grain scratching.
3After sanding, wipe the door clean again.
4Apply at least one primer base coat and let it dry thoroughly. Apply a second coat if the wood is porous.
5Apply a minimum of two coats of finish paint, making sure to allow for adequate drying time between applications.
6Rehang the door after it is thoroughly dry.
7Install airtight and watertight seals if the patio door opens to the outside.
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