The quantity of effort you want to put into restoring an old door is dependent largely on whether or not it is an outside door. If the door is not exposed to the weather, you may be able to get by with a touch-up. Sun and rain wreak havoc on most finishes, though, and you will probably have to strip an outside door and sand the wood to do a decent restoration. While it’s possible to strip and sand a doorway whenever it’s hanging, it is much easier — and you will do a much better job — should you take it down.
Pull the hinge pins and then take down the door. Lat it flat on a set of sawhorses and cover the floor using a drop cloth.
Take off all the door hardware, including the knob, latch and hinges, with a screwdriver. If the door has a window, cover it with masking paper and tape.
Eliminate up to the old end as you can by scraping both sides of the door gently with a pull scraper. If the finish does not come off easily, don’t force the scraper, or you will mar the doorway. If the doorway is an inside one, then you may be able to revive it by staining over the old end and applying a new finish. If so, prepare the doorway by sanding it gently with 220-grit sandpaper, going with the grain of the wood.
Strip off the old finish using a chemical stripper containing methylene chloride. Paint a thick coat onto a single side of the doorway and scrape it off using a paint scraper once the finish softens. Apply more stripper if any end stays. Neutralize the stripper by massaging the doorway using a rag soaked with mineral spirits, then strip the other hand.
Sand the door down to the bare wood after you strip it. Utilize a palm sander and 100-grit sandpaper to get off any remaining old end, then switch to 120-grit paper to smooth the wood. Finish by hand-sanding using 150-grit sandpaper.
Stain the doorway by brushing stain on the surface using a paintbrush and wiping off the excess with a rag. If you didn’t strip the doorway finish, make sure the stain you’re using matches the stain already on the doorway.
Top-coat the doorway by brushing on a transparent finish. Polyurethane varnish works nicely for inside doors, but if the door is exposed to the sunlight, use spar varnish. It provides greater UV resistance.
Allow the first coat of finish dry, then flip the doorway over and paint the other hand. Hang the door following the end on that side of this doorway dries, but don’t put in the knob or binder nevertheless. Put a drop cloth on the floor below the door.
Sand both sides of the door gently with 220-grit sandpaper, then paint a second coat of finish on either side. Sand again and employ a third end if necessary. Replace the hardware following the previous coat dries.