How to Apply Varnish to a Room Door

Place two saw horses in an area that stays between 70 and 80 degrees Fahrenheit. It is best to do this outdoors, but if the weather is cold, you can do the job indoors. Make sure the room has is adequate ventilation and that the floor or furnishings are covered with a tarp or drop cloth.

Lay the door on two saw horses and remove all the hardware with a screwdriver. Put the hardware in a safe location so you can put it back on the door once you've finished applying the varnish.

Sand the wood door with 150-grit sandpaper. You can use a handheld sander or fold a piece of sandpaper into fourths and sand the surface by hand. Vacuum the dust left behind with a shop vac.

Change the sandpaper to 180-grit and sand the surface again. Vacuum the dust left behind. Wipe the surface with a tack cloth.

Inspect the wood door for any cracks, deep scratches or holes that aren’t supposed to be there. Fill in these areas with wood patch. Press the wood patch into the crack or holes with a putty knife. Leave the wood patch a little higher than the surface of the door. Try to match the wood putty with the color of your door. Leave the wood patch to cure according to the manufacturer's directions. Do only one side of the door at a time, allowing the patch to dry completely on each side.

Sand the area with 220-grit sandpaper, moving over the area where the wood patch is covering the crack. Sand it until the patched section is level with the rest of section on the door. If you need to apply more wood putty, repeat step 5 until you are satisfied with the results.

Stain the wood with a brush or clean rags. Stains can range from light to dark, and you can mix and match to create a custom stain. Experiment with a scrap piece of wood first to make sure you like the color. Work in sections at a time and blot up the excess stain. The longer the stain remains on the wood before you wipe the excess away, the deeper the color will be. Allow the stain to dry according to the manufacturer's directions. Change rags often or you won’t be removing the stain, you’ll be reapplying it. Only do one side of the door at a time, allowing the stain to dry thoroughly before doing the other side.

Brush on a thin coat of varnish. Leave this to dry for two hours.

Sand the wood door with 220-grit sandpaper. Vacuum away the dust and go over the surface with a tack cloth to ensure that all the dust is removed.

Apply a second coat of the varnish. Allow the varnish to dry according to the manufacturer’s directions before reinstalling the hardware and installing the door.