Glass Cleaning Process

 Of the questions I get asked about vehicle detailing the one that is asked most often is on glass cleaning (followed closely by how to care for leather upholstery) BTW 15 to 20% of a car’s surface is glass. 

Looking at glass under a microscope you’ll see that its surface has many peaks and valleys to which water, minerals, and soap residue and environmental contaminates can cling to these pitted surfaces, all of which requires regular cleaning.

Water ‘spots’- there are two categories of water mark (the so-called water spots)

Stage I (Surface) Corrosion [: defined as a surface with light to moderate corrosion damage to the paint surface]

Stage II (Sub-surface) Corrosion [: definition when the dirt/corrosion deposits are no longer on the surface but have started to break down the molecular structure, leaving an etched or white haze on the surface( a concave circular mark ) after the stain has been removed, with moderate to serious paint damage]

 a) Surface water spots- (Stage I Corrosion) alkaline watermarks consist of calcium (Ca) and magnesium (Mg) both of which are basic (alkaline pH 10) that alight on the surface; ultra violet (heat) radiation (UVR) will leave a white ‘water mark’, the minute crystals bond to the surface, they will not wash off as they are insoluble and if left for any length of time they will etch the paint film surface leaving a concave circular mark, remove surface deposits with detailer’s clay and an acetic acid pH 2.0 (vinegar) to naturalise the alkaline

b) Below surface (etched) spots- (Stage II Corrosion ) are caused by an aggressive alkaline or an acidic solution (acid rain, bird excrement or industrial fallout) causing a chemical reaction, if left for any length of time they will etch the paint film surface leaving a concave circular mark. Unlike water spots which typically have a white outline of the spot, acid rain etching is smaller and you can see the damage in the clear coat.

Ratings for Different Types of Windshields on the Mohs Scale Windshields are a crucial piece of safety equipment on aircraft, cars, buses and other vehicles. Aerodynamically designed, windshields typically consist of an inner cellulose layer covered by two layers of glass; one on the outside and one on the inside. Since shattered glass from windshields can cause serious injuries or fatalities when a collision occurs, it's important that the vehicle's windshield be strong.

Referring to the Mohs scale is a good way to discern the relative toughness of a windshield. There are two main types of windshields: Tempered glass windshields and Laminated safety glass windshields (more common). 
The ratings of these vary on the Mohs scale.

Laminated Safety Glass Windshields
In a laminated windshield, a layer of clear plastic (typically cellulose-based) is blanketed by two standard glass planes. This type of windshield is most common and scores between a 6 and 6.5 on the Mohs scale, making it harder than regular glass (5.5), but not as hard as emerald (7.5). Though this kind scratches somewhat easily, they're designed well. When the windshield breaks in a collision, the interior plastic layer holds the glass shards, protecting the driver and passenger from getting cut.

Tempered Glass Windshields
Are heat-treated to harden the glass surface (on the outside, not inside) and enhance scratch resistance, tempered glass windshields are harder than laminated varieties, rating a 7 on the Mohs scale. The tempering also has another effect; when the glass breaks, it's designed to shatter into tiny chunks instead of big jagged pieces. This decreases the likelihood of serious injuries.

Rock chips
These micro-chips are caused by road grit impacting the glass surface, they appear as ‘white spots’ when filled with a wax or polymer sealant. In a recent windshield damage study conducted by the Motor Industry Research Association (MIRA), it was found that; extreme temperatures and structural fatigue will cause existing windshield chips to spread quickly, requiring glass replacement.

Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts, this differential expansion and at some point this stress overcomes the strength of the material, causing a crack to form. If nothing stops this crack from propagating through the material, it will cause the object's structure to fail. This occurs if you wash a cold surface with warm / hot water or conversely a warm / hot surface with cold water Thermal shock can be prevented by reducing the thermal gradient seen by the object ( i.e. by changing its temperature less rapidly)

In cold weather conditions, windshields will develop a more concave shape. As a result, windshield chips and dings are more likely to spread in a horizontal fashion. Chips were likely to spread more than 80 percent of the time at temperatures of 14 degrees (-10° C). Those tested at 32 degrees were nearly 60 percent likely to crack. Warm weather conditions cause windshields chips to spread more vertically. The same study conducted suggested that the heat itself distorts the shape of the windshield glass, which can lead to cracking by itself.

However, it was also found that the cooling effect of the air conditioning unit is likely to set off a crack. Driving over a speed bump, pothole or other uneven terrain can cause a chip to crack. The force radiates through the car and puts additional pressure on the edges of the chip, which can quickly lead to a crack. Although it is not possible to suggest how long it will take for a chip to spread, the study suggests that stressors like weather changes and simple driving will eventually cause or lengthen a windshield crack.

What kind of damages can be repaired?
Many glass polishing products can’t actually remove etched spots, but will thoroughly clean and fill them (Kaolin clay) so they appear virtually invisible. However a windshield repair is a process that uses skill to repair stone damage on a windshield instead of replacing it altogether. Stone damage or stone "chips" up to the size of a quarter, if you can catch your fingernail in the scratch 0.4 Mil (10µ) deep, you should consult a professional auto glass company Best results are obtained when the damage is repaired right away, before contamination occurs from car washing, road grime, or inclement weather.

Once the surface has been washed and cleaned (detailers clay) any minor imperfections can be removed with an abrasive glass polish (CarPro CeriGlass, Autoglym Car Class Polish or Zaino Z-12 Clear-View Glass Polish) These products remove "light" scratches, acid water spots, bird and bug stains, including alkaline mineral deposits, and then smoothes out etched glass (See article “Polishing Glass”) 

 Windshield Haze or ‘Fog’ (Interior) 
The vinyl used on vehicle dashboards contain diethylhexyl phthalate (DEHP) plasticizers, these low molecular weight compounds maintain semi-rigid vinyl’s flexibility. The vinyl used in modern vehicle interiors vent (out-gassing) these are the plasticizers evaporating (more prevalent on newer vehicles or a dash with freshly applied vinyl dressing) Crack open vehicle windows when parked to allow the gasses to vent and do not use any vinyl protection product for fifteen days or so on a new vehicle. 

Ultra violet (UV-A) heat radiation will also cause the plasticizers to dry out, resulting in a chemical film that when combined with road oils, dirt and grease introduced via by the vehicles AC system or smoker's residue, which results in a stubborn haze or fog that forms a cohesive bond with the interior glass surfaces. 

For severe out gassing or the removal of stubborn grime; spray the glass surface (otherwise you are diluting the product strength) with 1:10 solution distilled water /Isopropyl alcohol and wipe with a clean cloth and the result is a crystal clear finish. You may need to repeat this process Ensure that all cabin fabrics (seats, carpets and mats) are thoroughly dry; otherwise their moisture evaporation will exacerbate the problem 

Glass Cleaning
Looking at glass under a microscope you’ll see that its surface has many peaks and valleys to which water, minerals, surfactants and car wash soap residue and environmental contaminates can cling to these pitted surfaces, all of which requires regular cleaning / removal. A dirty or distorted windshield and/or worn wiper blades are dangerous; 90% of your driving decisions are based on a clear, unobstructed view of the road, it's a critical safety concern that your car's wipers provide you with the cleanest windshield possible. 

Wiper blades should be checked for wear and replaced annually or when showing signs of wear. Dirty windscreens add to the danger when the sun is low. If you can't see, slow down accordingly, keeping an eye on the traffic behind, in case the following vehicle doesn't see you against the sun. As it makes driving safer allowing you to see the road ahead clearly, it enables the glass to defrost even quicker and removes the contaminants that contribute to the oily film on the glass, driving, especially on a dark and rainy night without being able to see through the windshield is to say the least, impairment. 

Ghost’ marks (from suction cups or wiper blades) - factory glass is installed with the help of strong suction cups to assist in its placement, they are lubricated with a special release agent compound, this helps the air suction applied to be broken. 

Unfortunately they often leave marks that are only visible in direct sunlight. These can usually be removed (least abrasive first) a chemical paint cleaner (P21S Paintwork Cleanse) detailer’s clay or a glass polish (Autoglym Car Class Polish or Zaino Z-12 Clear-View Glass Polish) agitation with a soft brush or a terry cloth towel helps to clean out the micro pores of the glass. 

If the above methodology fails to remove them use a diluted Cerium Oxide (CeO20) / distilled water solution Exposure to bugs, road oil and tar, and catalytic converter emissions makes automotive exterior glass cleaning a challenge. The film on the inside of your windows is caused by "out gassing" of the plastic and vinyl components of your interior. Ammonia is harmful to many car surfaces including vinyl, rubber, and leather; there is also a potential danger of becoming asphyxiated without adequate ventilation. A newly detailed vehicles appearance would be ruined with soiled glass surfaces. All it takes to rectify is a little time, the correct method and cleaning products for crystal clear clean glass and plastic. 

The difference clean glass surfaces make to a detailed vehicle is night and day. Put your hand in a plastic sandwich bag and lightly run your fingertips over the windshield's surface. Chances are, it will have a rough, gritty feel, and glass cleaners will not remove this grit. Window cleaning has always presented a challenge for professional and enthusiast detailers, both demand perfection with streak-free, crystal-clear glass. But without using the correct methodology, the correct towel and the correct product required to produce perfectly clear glass surfaces every time 

Application Technique Water in whatever form of filtration / purification is a very good solvent; however on its own it will not dissolve grease, oil, road dirt or the plasticizers that outgas from vinyl. I usually advocate spraying car care products on to a towel and not directly onto the surface being detailed. The exception to this is when cleaning glass, rather than letting the cleaner soak into the towel, which results in insufficient product as a large majority is absorbed by the towel, better results will be achieved by soaking the dirt / grease residue on the glass surface. 

 Use a fine mist directly onto the glass surface, allow to dwell if it starts to dry, re-mist. Glass cleaning products contain a combination of ingredients including alcohol, ammonia, and detergents that will clean, but may also cause steaks. 

Depending on how fast or slow these ingredients evaporate, and their concentration, streaking problems may occur. The residue from these ingredients sometimes dries and evaporates on the glass before they are removed .As with all chemicals they need a certain amount of time to work, so allow area to soak for a few minutes, dry the glass with a clean, dry towel. For each area of glass use the clean side of a folded towel If there is condensation on the glass, use the vehicles heating and / or air conditioning to remove the moisture. Moist cold air and damp towels will exacerbate the moisture making it pretty much impossible to clean glass surfaces. 

Glass Cleaners 
There are dozens of different companies who make glass cleaner. Using alcohol and white vinegar together makes a quickly evaporating glass cleaner 8 oz. isopropyl alcohol (IPA) 8 oz. distilled water 0.25 oz. white vinegar All you need is the right glass cleaner, a glass towel, and the correct technique to get clear, practically invisible glass. For truly clean, streak-free glass, mist one side of the windshield with the glass cleaner of your choice; use the folded towel to wipe up and down the glass in long strokes. Then wipe side to side in long strokes. Flip the towel to the dry side and wipe the glass again in this method. Then move on to the other side of the windshield and on to the rest of the windows. You may not be able to clean it perfectly the first time. Repeat the above process and continue to wipe in long strokes. Always finish by wiping the glass with a dry side of the towel to eliminate streaks. 

Dr Joe dedicated Lint-Free 100% Cotton Surgical Towels, that have a tight cotton herringbone weave and a thread count of 170 per square inch, which is ideal for hard surfaces like glass as they have more ‘grip’ than micro fibre towels and helps to break up the surface debris. Fold the towel in half and then half again. Mist the glass surface with 1:1 ratio of distilled white vinegar and water solution in a spray bottle or Stoners Invisible Glass™ Trigger Spray Bottle. 

Use one towel for product application and one for removal / buffing. In hot, humid weather conditions spray and clean one window at a time Once the glass has been thoroughly cleaned, wipe it dry. Using two clean micro-fibre Waffle Weave towels soak one it in clean water and wring it almost dry. Wipe the glass and then using the other towel dry the glass completely. Once glass surfaces are clean and dry protect it with a sealant or wax. 

 Washing/ Care- reserve two Waffle Weave towels for glass cleaning .Wash these towel with distilled white vinegar (no detergent or fabric softeners) Drying Pattern Use a different drying pattern for interior / exterior glass surfaces (i.e. horizontal for interior and vertical for exterior) utilizing this technique you can easily determine the location of any streaking. A waffle weave towel is excellent when used for this purpose 

 Alternative Products – a)Optimum Glass Towel- that is also lint free and cleans glass without chemicals, making glass cleaner chemicals virtually obsolete, slightly dampen the towel with distilled water and the results will be crystal clear  
b)Ultra-51 Glass Towel- It has no nap, making it very similar to a huck towel but with the added benefit of micro fibre technology – Towels by Dr Joe Washing/ Care - rinse cloth thoroughly or wash prior to first use, always use cloth damp. Simply wet it with water and wring it out well. If you're getting water spots that stay on your surface; you have too much moisture in your cloth. Wash with liquid soap, but do not use fabric softeners, hand or machine wash cloths alone or with lint-free clothing. Bleaching is great for disinfecting the cloth (DO NOT use bleach on Microfiber). 

 Fabric softeners coat the cloth which can cause streaking and can also keep the patented fibres from being able to pull the dirt from your surfaces. Allow to air dry, without any dryer sheets Kitchen paper towels have lanolin in the fibres and will leave streaks. 

Newspaper are currently recycled, and most are formulated with adhesives, which class cleaners will break down leaving a tacky reside and paper ‘lint’ on the glass surface. The inks used and some chemicals can allow ink transfer to the glass. Newspaper inks are now water-based (unlike the older oil-based they will not shine glass) But they will stain your hand black (they dissolve with body heat) so be careful what surfaces you touch after handling newspaper (fabric, leather, plastic, etc.) as they may stain. 

Caution - Do not use products that contain ammonia, as it is very harmful to vinyl, plastic and rubber. It will cause plastic to ‘yellow’ and become clouded and it will also turn Mylar (plastic) window tint purple and may have a negative effect on the adhesive. Some people prefer to use plain water to clean their windows. While this is a very safe method, but water is sometimes not enough of a solvent to cut the protein base of stubborn grease / grime spots (use a 1:10 solution distilled water /Isopropyl alcohol) Side window felt Using a micro fibre towel and an old credit card, dampen the micro fibre with a 1:1 diluted solution of isopropyl alcohol/distilled water and wipe the felt 

 Drying / buffing glass Once the glass surface has been cleaned use a waffle weave micro fibre towel to final clean and polish the glass, when they are wet they’re very soft and super absorbent, and glide easily over the surface, the ‘pockets’ in the weave ‘hold’ any dirt or surface debris unlike some other super absorbing products that trap dirt between the towel and paint surface with the potential to cause serious scratches (never use it when it’s dry as it can potentially scratch) That goes for whatever you use for drying, including cotton towels. To use ensure that the towel is really wet and then wring it out thoroughly before using. 

 Non-Lint Surgical Glass Cleaning Towels Although the name suggests that these towels be used inside operating rooms, surgical huck towels are great for a lot of other detailing uses. Surgical huck towels are made from 100%cotton; they are lint free and have excellent absorption. For cleaning and drying windows, soft enough to polish and finish plated metals; these surgical towels are terrific for removing the cloudy film on windows. Use with a glass microfiber towel for perfect glass. Large sized (16 x 24") Towel care 

Always wash Lint-Free Surgical Towels and any glass cleaning micro fibre towels separately do not use fabric softeners but add a teaspoon per towel distilled white vinegar in place of a softener, the vinegar doesn't coat the fibres but instead works to eliminate detergent residue and the acid counteracts any alkaline minerals in the water supply. 

Vinegar (Acetic acid, pH 2) works well in the rinse cycle to make your towels softer. Detergent is an alkaline (pH 12, the opposite of acidic on the pH scale). 

External Glass 
Use detailer’s clay to remove road debris, brake dust, tar, etc. I would not advocate the use of synthetic steel or brass wool on glass surfaces; the reasons being are that no matter how fine of a grit (even #00000) you use you are actually micro scratching the surface of the glass allowing more spaces for dirt to build and settle where normal washing will not remove it, even though the glass looks super smooth to the naked eye. Grades of steel wool are similar to grit in finishing papers; the finest steel wool is grade #0000 steel wool or 1000 grit 

A better way to clean glass would be to use a Hi-Tech Body Sponge™ this innovative rubber polymer product safely and easily removes water spots, tree sap, rail dust, bugs and other bonded surface contaminants from the surface of automotive glass, mouldings and, may be used with any kind of lubricant and being an abrasive it will also produce a shine. With rubber side down, gently rub Body Sponge on glass using diluted car wash soap as a lubricant 

Glass Protection
 Once external glass surfaces have been cleaned apply an acrylic polymer as a rain repellent / protectant to help keep glass clear and cleaner for longer. Durable windshield and glass coating provides unsurpassed protection and water sheeting to provide clear vision Optimum Opti-Glass Coating forms a durable, cross-linking bond to glass and other silica-based surfaces, providing the utmost in chip, scratch and mar resistance. This coating creates an immense amount of surface tension on glass surfaces that water will simply bead up and roll off at speeds above 35 mph, rendering your windshield wipers virtually unnecessary at highway speeds Rain, sleet, ice and snow will not stick to treated exterior glass surfaces, providing you with a clearer view of the road ahead. 

Optimum Opti-Glass Coating lasts up to a year and is incredibly easy to apply for maximum protection apply the coating first and maintain the protective coating using the Opti-Glass Clean & Protect Directions: Apply within a surface temperature is between 60°-90° F (15°-30°C). Do not apply in direct sunlight. Thoroughly clean surface and use a product to remove bonded contaminants. 

 Polish glass if scratches are present. Before applying, wipe glass down with a 1:15 solution of isopropyl alcohol /distilled water. Spray Opti-Glass directly onto foam applicator pad and apply in an overlapping, circular motion. Allow Opti-Glass to cure for 2 minutes and remove excess with a clean, dry microfiber towel. Alternate Products Klasse All-In-One) Gtechniq G1 Clear Vision Smart Glass 

Relevant Articles

1.“Polishing Glass” - http://www.autopia.org/forum/guide-detailing/137878-polishing-glass.html#post1464140