Window Cleaning
by Paul Gasparola and Angela Brown
Professional Detailers Association

Getting windows clean without streaks is a challenge even for the most experienced detailer. However, using the right chemicals, equipment, and procedures from the start can help prevent this problem.

Just as in choosing car wash soap and wax, no two car enthusiasts can agree which window cleaner is best.

Wet Spray works fine overspray
2-3 applications necessary
Foam Spray works fine overspray
dries fast
Liquid Soaps will clean must rinse glass with clear water to remove film that will be left behind
Ammonia with water
Ammonia-based Cleaners
cuts grease & helps water evaporate quickly ammonia can damage and even melt window tint 2 applications necessary
Alcohol-based Cleaners works fine, safe for window glass tint
cuts grease
must dilute according to manufacturer's directions

Regardless of what glass cleaner you use, prevent the solution from dripping on the painted surfaces or upholstery. If need be, lay a clean towel over the paint, dashboard or seat, just for protection. Have a supply of low-lint or lint-free towels that are dedicated only to window cleaning. Store and wash these separately from your other detailing towels. This will reduce the chance of waxes and silicones getting into the window towels.

Wash the window towels with a minimal amount of regular detergent. You can add cup vinegar to a full load to help remove detergent residue. Do not use fabric softeners or anti-static additives in the wash or dry cycle. These chemicals actually reduce the absorbency of the towels and will also leave residues that can cause streaking during normal window cleaning.

It is often better to spray the window cleaner onto the towel instead of directly on the glass surface. In the interior of the car, the overspray from direct spraying can get on neighboring surfaces that have already been cleaned. The interior (e.g., leather) may also be damaged by window cleaning solvents. On the exterior, wind-carried overspray can spot the painted surfaces that you just spent a lot of time beautifying. Start cleaning the glass surface by first framing the window, that is wipe the outside edges. Then, use a back-and-forth, crisscross motion across the "body" of the window.

If the windows are particularly dirty, you may need to clean them twice (much like "two-step" paint reconditioning). The first pass is to get the bulk of dirt and grime off the windows. The second pass, using a fresh set of towels, cleans and buffs away any remaining streaking. When you're finished cleaning the windows, take the car out in the sun if possible, get in the car, and look through every window, checking for streaks. Clean (again) and touch up the windows as necessary.

Start with the driver's door. Roll the window down about an inch or so. This will allow access to the top part of the glass hidden in the upper groove along the frame. Clean and dry this part first. Then roll the window back up and clean the rest of it. Take note of the corners. Take your time and inspect each window before moving on. Don't forget the outside mirrors. Rear windows are the most difficult to clean. Use the back of your hand, a towel wrapped around a painters stick to guide the towel, or mitt. If necessary, unfold the towel and use a corner of it for more manageability.

Spray a toothbrush with the window cleaner or dip it in water; shake off the excess. Scrub along trim and molding to break loose the crud. Use the fold of a thin towel to reach into the seam and remove debris. A cotton swab can be used in tighter spots. If a toothbrush isn't strong enough to break up the build up, you can gently slide the blade of a razor scraper along the glass and under the dirt. Carefully raise the back of the scraper to loosen the dirt. Follow with the toothbrush and towel. Use a razor scraper with special care. Inserting it too far into the molding may cause leaks; a slip could end in a scratch or tear if too much pressure is applied. Save this tool as a last resort.

Some parts of the country are burdened with extremely hard water. So hard, in fact, that it can etch and water spot glass. For this special problem, clean the glass first with water. Gradually increase the strength of cleaning methods, using cleaner, glass polish, or #)) or finer steel wool.

Film-tinted windows that are dirty can be cleaned with cleaners marked "safe for Mylar tint". If cleaned with ammonia or ammonia based cleaners, this will damage the tint. For clear plastic or tinted plastic windows, use cleaners (Novus) designed for plastic windows on ragtops. They come in a spray and are safe for use on plastic, Plexiglas, and window tint film. Plastic windows can also be polished using available clear plastic polished and cleaners. These can be applied by hand. This is important for convertible tops that have a plastic rear window. You have probably seen many plastic windows that have become opaque or even brown with age, neglect, and inappropriate cleaning products.

Heavy Window Cleaning

Exterior glass surfaces may have staining and micro-scratches that may be removed using stronger cleaning techniques. You may also notice spots and blotches that appear as you wipe window cleaner across the glass; the window cleaner does not remove the spots but they disappear when the window is dry. The truth is, the spots and stains are still there and will reappear each time the window is cleaned. These stains and etchings reduce the clarity of the glass. Most of the major chemical manufacturers offer a glass polish product that is formulated for heavier cleaning.

Glass polish can be applied by hand with a wax applicator, a mild scrub sponge (the kind that will not scratch nonstick-coated frying pans. Buff the polish across the window using a back-and-forth, crisscross motion to ensure coverage. Then wipe the residue with a towel. Repeat as necessary until the window is polished to your satisfaction. Then clean the window with normal glass cleaner, as mentioned above. Be aware that heavy glass polishing is illegal in some states because it can change the optical neutrality of the window.

Checklist for Success


When cleaning windows, take your time, use good materials and check your work in the daylight. Remember, the windows are one of the last things you clean when detailing your car but they are the first thing people notice.

2002 Paul Gasparola and Angela Brown: Members - Professional Detailers Association