Painting a Window Sash
Credit: Opensource


A window sill and outer casing degrades naturally over time due to moisture and ultraviolet rays from the sun.  Therefore every homeowner should perform periodic maintenance on windows which may include sanding and striping the wood frame of the window.

Most windows in the last few decades have been sealed with either an oil or water based polyurethane. While either will do the job, for the average home owner, the water based version may be a better choice because it is easier to clean up.

Before You Begin

There are a few things you need to have around the house before you begin staining your windows.

  • Paint and varnish remover
  • New stain, varnish and clear finish
  • 120 and 180 grit sand paper and steel wool
  • Wood putty and putty knife
  • Painter’s masking tape
  • Cleaning product for glass
  • Paintable caulk
  • Rubber gloves
  • Respirator and appropriate cartridge
  • Utility knife
  • Sash brush and window scraper
  • Drop cloth, old rags or paper towels

Be sure to pay attention to the labels on the cans of stain and varnish you choose. Both do different things. For instance, stain consists of many dyes and pigments that alters the color of the wood.

However, varnish contains resins that offer protection against the sun and moisture.[1] Neither type does both jobs, so if your goal is protection, make sure to choose a varnish because it will be able to stand up to time and the elements on its own. Stains offer no protection, just a color change.

So if you are going to stain the wood, use both and apply the varnish over the stain to give it a better sheen.

Sanding and Stripping the Wood

If you are redoing a varnished surface, you do not have to remove the old finish because modern varnishes will stick to whatever is underneath. However, it is imperative that you clean and prep the wood.

Prepare your work area by laying a drop cloth on the floor or work table in the garage. This job will go faster if you remove the upper and lower sash. If this is not possible, the job can be performed with the window in place. For this discussion, I will assume that you are able to remove both parts of the window if it is double-hung.

To remove existing paint (and if you feel it is necessary to remove the existing varnish) follow these steps:

  1. If the window is in good condition, sand it with 120 grit sand paper to create a dull sheen over the wood. Next, wipe it down, then sand once again with 180 grit sand paper so the wood is completely smooth. 
  2. Brush paint or varnish remover following the manufacturer’s instructions on the can. Most store bought liquid strippers will remove 90% of all clear finishes.
  3. Use short stokes moving quickly back and forth over small sections as a time. Do not over brush because it leaves brush marks.
  4. Then using a putty knife, scrap off the remaining finish and rinse with the recommended solvent. This will remove the existing finish so you can start from scratch.

Note: If you are removing paint and you suspect that it may contain lead, use the appropriate safety goggles and respirator and use a peel and strip paste stripper which removes the paint without any fumes, chipping or flaking.

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Repairing the Frame and Surface of the Window

Inspect the window frame damage to the wood.  Stain does not hide imperfections so it is important to repair, sand and seal the wood before applying the final coat.

  1. Use a stainable wood putty that is as close a match as possible to the existing wood to fill in holes, then sand those areas after the putty dries.
  2. Use a wet paper towel and wipe the sanding dust away.
  3. Lightly go over the entire areas where you used wood putty with steel wool.
  4. Protect the panes of glass within the frame by applying masking tape around the edges. 
  5. When choosing tape, choose the low-tack tapes that are easy to remove from any surface.
  6. Be sure to mask edges of each sash where they meet to prevent sticking in the future.

Choose an Interior Oil Stain

How to Stain a Window
Credit: mjpyro

Apply the Stain

Now that the wood has been stripped and prepped, you are ready to apply the first coat of How to Stain a WindowCredit: Opensourcestain.  No matter what type of stain you have chosen, the finish will depend on how well you have prepped the wood and stripped the old varnish properly.

Additionally, if the window is made of a softer wood, use a gel type stain which will not create a blotchy look because it does not absorb deep into the wood.  If you try to use a regular stain on a material such as pine, it will absorb unevenly and you will not be happy with your results.

Apply at least two coats of stain, lightly sanding the entire frame and wiping it down with a cloth or damp towel between coats.

Lastly, apply the varnish which will add protection from moisture and UV rays.

Staining a Sash

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Clean Up

Once the stain begins to dry, remove the masking tape from the glass panes to prevent residue on the tape from sticking. Next, take a utility knife and run it along the edges of each pane, then use a window scraper to push the remnants of the tape toward the cut line.

If you removed the sash from the window, carefully install it back in place, and replace the trim.

Final Thoughts

Make certain to read all labels on the cans of whatever product you choose. If you are staining the wood frame of the window, then you should be applying a varnish as the top coat to protect it from the elements.

While it is best to apply both a stain and varnish, if you must choose just one, choose the varnish on the window because the stain provides no protection on its own.

The most important step to a clean, even look is preparing the surface area by removing imperfection and repairing any dents or dings before you begin.

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