How to Clean Interior Windows Without Streaks: Glass, Frames and Sills

To clean interior windows without streaks, work on a cloudy day or on glass that’s out of direct sun, vacuum the sill and frame first, wash the glass with mild soapy water or a glass cleaner, then pull it dry with a rubber squeegee or buff it with a clean microfiber cloth. Finish by wiping the frame and sill dry. Most streaks come from cleaner drying too fast or from a dirty cloth, not from the wrong product.

Inside glass collects fingerprints, cooking film, pet nose prints and a dusty haze that shows up the moment low afternoon sun hits it. Here is the order we use, what window makers say to avoid, and how to deal with the black spots that show up on sills when windows sweat.

What you’ll need

• A vacuum with a brush or crevice attachment for sills and frame corners.
• A bucket of warm water with a few drops of dish soap, or a standard glass cleaner. Andersen’s care guide also lists a 50/50 mix of white vinegar and water as compatible with its windows.
• A soft sponge or a microfiber scrubber.
• A rubber-bladed squeegee for larger panes (optional, but it’s the fastest way to a streak-free finish).
• Three or four clean, lint-free microfiber cloths, washed without fabric softener.
• An old towel to lay along the sill and catch drips.

How do you clean interior windows without streaks?

Clean when the glass isn’t in direct sun, remove loose dust before anything wet touches the window, use very little cleaner, and dry the glass before it dries on its own. A squeegee pulled in overlapping strokes, followed by a dry microfiber on the edges, leaves the fewest marks.

1. Pick your timing. Andersen notes that cleaning in direct sunlight can cause streaks because the product dries on the glass. Do sunny windows early, late, or on an overcast day.
2. Dry-clean first. Vacuum the sill, the frame corners and the bottom of the glass. Then wipe the glass with a dry microfiber. Dust plus water turns into gray smears.
3. Protect the sill. Fold a towel along the sill so runoff doesn’t pool on wood or drip down painted trim.
4. Wash the glass. Wet the sponge in soapy water and wring it well, or mist glass cleaner onto a cloth. Work from the top down. For sticky spots, hold the damp sponge on them for a minute instead of scrubbing harder.
5. Squeegee or buff. On a large pane, wipe the squeegee blade dry, then pull it across the top edge and down in overlapping strokes, wiping the blade after every pass. On small panes and divided-light windows, buff with a dry microfiber instead.
6. Detail the edges. Run a dry cloth around the perimeter of the glass where the squeegee can’t reach. This is where most leftover lines sit.
7. Check at an angle. Look across the glass from the side. Buff any haze with a dry cloth rather than adding more cleaner.

What should you never use on window glass?

Skip anything abrasive or sharp. Andersen’s care guide rules out steel wool, sandpaper and other abrasive tools, metal razor blades, alcohol-based cleaners and wipes, and pressure washers. PGT’s homeowner guide adds putty knives, petroleum-based products, caustic cleaners and hydrochloric or phosphoric acid. Newspaper is out too: Andersen warns the ink can stain glass and frames.

Two special cases are worth checking before you clean:

• Coated glass. Some energy-efficient glass has a coating on the interior side. Andersen tells owners of its HeatLock glass to use only mild soapy water to protect that coating. If you don’t know what glass you have, mild soapy water is the safe default.
• Window film or tint. 3M’s care sheet says not to wash newly filmed windows for 30 days, and not to use knives, scrapers, brushes or abrasive materials on film at any point. Wipe lightly, and squeegee the film dry rather than leaving it wet.

As with any cleaning job, use one product at a time and never mix cleaners. If a product label and your window manufacturer’s care guide disagree, follow the manufacturer.

How do you clean window frames and sills?

Vacuum them, then wipe with a cloth dampened in mild soapy water and dry them right away. PGT recommends mild soap and water for frames and a damp cloth or vacuum for sills and tracks. Treat the sill by its material, because wood, paint and stone each have limits, and test any cleaner on a hidden spot first.

• Vinyl and aluminum frames: soapy water and a soft cloth, then a dry cloth. Don’t use abrasive pads, which dull the finish.
• Painted wood sills and trim: wring the cloth almost dry and wipe gently. Water left standing on painted wood is what lifts paint and swells joints. Our guide to cleaning painted walls without damaging the paint covers scuffs and touch-up risks.
• Stained or sealed wood: a barely damp cloth and immediate drying. Skip vinegar on wood finishes.
• Marble or other natural stone sills: no vinegar, lemon or other acids, which can etch stone. Use plain water or a cleaner labeled safe for stone.

If the window slides, the track below it is its own job. Our step-by-step for cleaning sliding door and window tracks covers grit, weep holes and lubrication.

Why do my windowsills get black spots?

Black or gray spots on sills and in frame corners are usually mildew fed by condensation. When windows “sweat” on cool mornings, water runs down the glass and sits on the sill. Clean the spots, dry the sill completely, and lower indoor humidity so the moisture doesn’t keep coming back.

For small patches, the EPA’s guidance is to scrub mold off hard surfaces with detergent and water and dry completely. The EPA puts the do-it-yourself limit at a moldy area of less than about 10 square feet. Larger growth, mold that returns into soft or rotting wood, or spots that come back right after cleaning point to a moisture problem worth having looked at.

PGT’s guide notes that condensation on the room side of the glass comes from indoor humidity, not from a faulty window, and suggests running exhaust fans longer, opening blinds and drapes, cracking a window daily or using a dehumidifier. Fog or moisture between the panes of a double-pane window is different: it means the seal has failed, and no amount of cleaning will clear it.

How often should you clean interior windows?

For most homes, washing interior glass a few times a year and spot-cleaning handprints as they appear is enough. Sills are a weekly or every-other-week wipe, because dust settles there fast. Kitchen windows near the stove, sliders that kids and pets touch, and windows that collect condensation usually need attention more often.

The days after a windy stretch are a good time for a pass, since dust settles on sills and frames first. If dust seems to coat everything in your home, our guide to why houses get dusty and how to cut it down explains where it comes from. And if you’re cleaning the whole window, do it in this order: blinds or shades first, then screens, then glass, then sill. Our guides to cleaning blinds and cleaning window screens cover the first two steps.

Windows, mirrors and glass doors: what’s different?

The squeegee-and-soapy-water method works on windows and glass doors because they’re sealed units that tolerate a bit of water at the edges. Mirrors don’t: liquid that seeps behind a mirror damages the silvering. If you’re moving from windows to mirrors, switch to the barely damp cloth method in our guide on how to clean a mirror without streaks. Fireplace glass is different again: it needs a fully cooled fireplace and a cleaner made for it, never an ammonia window spray, as our guide on how to clean fireplace glass explains.

When interior windows are part of a bigger clean

Here is how window work fits our services, as listed on our service pages. Interior windows aren’t part of a standard recurring cleaning visit, but they can be added, and window tracks are included when you add them; windowsills are dusted on every recurring visit. A deep cleaning also offers interior windows as an optional add-on. Every Move-In/Move-Out Cleaning includes reachable interior windows and sills. Our window work is interior only (exterior windows aren’t part of the Move-In/Move-Out scope or the window add-on), so outside glass, second-story panes and skylights are jobs for a window-washing company.

Our Vetted Cleaning Professionals follow the same order described here: dry dust first, a light hand with product, and glass dried before it can streak. Suddenly Clean serves homes throughout East County and surrounding San Diego communities. If your ZIP code is accepted, we currently service your area. You can see your exact flat-rate price on our booking page before you book.