The most likely cause of smearing or streaking after cleaning your windows is residue left on the glass from the cleaner you’re using. Consider diluting the solution and cleaning them again, or use old newspaper to dry the windows after cleaning, as this will soak up any residual material. Additionally, aim to clean your windows on a cool, cloudy day, as cleaners will dry more quickly on the glass if it’s hot and sunny, promoting streaking.

The best way to clean outside windows is by using a garden hose. Start by spraying the windows with a high-pressure stream to clear off loose dirt and grime. Then use a mixture of hot water and dish soap and scrub the windows with a sponge. Rinse off the soapy water with the hose. Before you finish up, spray the windows with a solution of vinegar and water and wipe them down with a microfiber cloth.

For a standard 1,000-square-foot home, you should expect your window cleaner to take between 1 and 3 hours to clean all of your windows. Of course, the size of your home and the number and size of the windows you have will play a role in the timeline. Certain styles of windows—like picture windows, which have no moving parts—also take less time to clean.

Professional window cleaners typically use either a white vinegar solution or a commercial hard water stain remover to clean hard water stains on windows. A common vinegar solution for this purpose consists of one cup of white vinegar mixed with a gallon of distilled or bottled water. The pro will spray the mixture and lightly scrub the window with a scrubby pad before cleaning with a standard cleaning solution. Alternatively, they may use a commercially available hard water stain remover and a scrubby pad, followed by a complete cleaning.