I spent an entire summer with one bedroom window that would not open. It was painted shut by the previous owners — I assume sometime during the Bush administration. When I finally fixed it in under five minutes, I was annoyed at myself for waiting so long.

Here is what worked.

Figure out why it is stuck

A window gets stuck for one of three reasons: paint sealing it shut, swollen wood from humidity, or gunk in the tracks. The fix is different for each, but all three can be solved without calling anyone.

Painted shut: Break the seal

If paint is bridging the gap between the window sash and the frame, slide a putty knife or a utility knife into the seam and run it all the way around. Cut through the paint on all four sides. Do the inside and the outside if the window has been painted from both sides.

If the putty knife does not fit, use a window zipper — a tool designed specifically for this job that costs about ten dollars. It has a thin blade and a handle that gives you leverage.

After cutting the paint seal, try to open the window. If it still will not budge, tap the frame gently with a rubber mallet to break the remaining paint grip. Do not use a metal hammer — you will dent the wood.

Swollen from humidity: Lubricate

Wood expands in humid weather. Rub a bar of dry soap, a candle, or paraffin wax along the tracks where the sash slides. The wax lubricates the wood-on-wood contact and the window will slide open.

Do not use oil-based lubricants like WD-40 for this — they attract dirt and eventually make the problem worse. Dry lubricants only.

Gunk in the tracks: Clean and wax

Vacuum the tracks first to remove loose debris. Then wipe with a damp cloth. If there is hardened gunk, scrub with an old toothbrush and a little dish soap. Dry thoroughly, then apply the wax or soap lubricant.

For metal tracks, use a silicone spray lubricant instead of wax. Silicone is dry, does not attract dirt, and works on metal-to-metal contact.

Prevention

Open and close each window at least once when the seasons change. Once a year, clean the tracks and reapply wax. If you paint the window frames, wait until the paint is fully dry — at least 24 hours — before closing the window. Otherwise you are just painting it shut again.

My bedroom window now opens with two fingers. I get a cross breeze through the whole apartment. It cost me a candle from the kitchen drawer and five minutes.