Environmental damage to paint comes in a varied range of threats; acid rain, industrial fallout, brake and rail dust, road salt, tree sap, hydrazine an extremely active acid that is found in jet fuel, ultra violet (UV) and heat radiation, and other airborne contaminants are very detrimental to a vehicles paint film surface.
They are all forms of environmental contamination and given the right catalyst; reactivity (heat) plus moisture, they will become acidic. During this process the metal absorbs oxygen from the water and forms iron oxide (rust). Given the porosity of paint they permeate the paint matrix down to body metal.
The rate of environmental exposure that negatively affects (clear coat) paint varies widely with ambient conditions (Ultra violet (UV) radiation.
Environmental Fallout, paint protection used, etc) but an approximation of 0.0005Mil (0.013µ) per annum is about average; protective coatings polymer sealants, wax, etc), being renewable are meant to be sacrificial (it is subjected to oxidation, thereby by saving the clear coat) It's better to have dust, road tar, tree sap, bug and bird excrement stuck to wax than your paint, wax also provides a limited paint (sacrificial) protection against acid (i.e. acid rain, environmental fallout and bird excrement
The clear coat provides protection to the paint matrix, this has a half-life (t 1/2) of five year and is defined in terms of probability [: the time required for exactly half of the entities to decay on average]
Environmental Fallout, paint protection used, etc) but an approximation of 0.0005Mil (0.013µ) per annum is about average; protective coatings polymer sealants, wax, etc), being renewable are meant to be sacrificial (it is subjected to oxidation, thereby by saving the clear coat) It's better to have dust, road tar, tree sap, bug and bird excrement stuck to wax than your paint, wax also provides a limited paint (sacrificial) protection against acid (i.e. acid rain, environmental fallout and bird excrement
Most natural contaminants are hydrophilic, automotive clear coats are generally based on urethanes, acrylics, melamine’s, silanes, etc. which are hydrophobic and repel water and other contaminants. However as the paint surface are subjected to photo-oxidation (sometimes incorrectly described as oxidation) water beading changes to sheeting and environmental contaminants will bond to the surface.
Automotive paint systems are porous; when you add water and heat to an acidic substance it will erode the paint system very quickly (the heat opens microscopic fissures in the clear coat allowing ingress, the water provides a carrier system for the acid, and heat acts as a catalyst each time water is reintroduced the acid will be reactivated). The paint surface should be periodically neutralized / decontaminated, i.e. once every two years (See also Reactivity)
Many natural and synthetic materials are attacked by ultra-violet radiation and products made using these materials may crack or disintegrate. This problem is known as ultra violet (UV-B) degradation, and is a common problem in products exposed to sunlight.
UV Radiation comprises both visible (UV) light and invisible (UV-A) infrared heat radiation, which represents part of the ultra violet solar spectrum (approximately 55%-60%). Organic (Carnauba) waxes or inorganic (polymer sealants or coatings) contrary to marketing myth do not contain natural ultra violet protection. Dependent on reflective value of the paint colour; surface reflection will provide some UV radiation protection along with some sacrificial protection as the wax or polymers breakdown.
Ultra violet stabilizer - providing protection from ultra violet radiation (UV) is very important to avoid photo synthesis (colour fading / yellowing) be cognizant that ultra violet heat (UV-A) radiation can also affect the structural integrity of materials by drying out and therefore removing their elasticity and causing cracks.
There is no such thing as a permanent UV stabilizer, it a matter of physics, not chemistry. Ultra violet protection is a sacrificial and therefore a renewable protection; this is due to the UV protection layer being degraded by exposure to the elements (sun, sand, road or sea salt, and etc) so it is imperative that you renew it and it needs to be re-applied on a regular 45 to 60 day basis (dependent upon location climatic condition)
Dependent on reflective value of the paint colour; surface reflection will provide some UV radiation protection along with some sacrificial protection as the wax or polymers breakdown.
Some waxes and polymer sealants have ultra violet (UV) protection agents added when they are formulated, but be cognizant that the protection a microscopically thin layer can provide is limited. This renewable barrier is probably less than 0.1 µ (4 Mils) thick. The primary paint surface protection against UV light is the clear coat; which protects the colour coat from fading by adding anti-UV chemicals to the polymer when mixing the clear coat ingredients.
This renewable barrier is probably less than 0.1 µ (4 Mils) thick. Clear coat paint (polyurethane) provides the colour and base coats with protection, and usually has UV protection added in the final coating; this tends to migrate towards the upper level of the clear coat (this is why it’s important to check how much of the paint surface you are removing with an abrasive polish). It should be noted that Carnauba wax does not contain a natural ultra violet radiation protection
Protection
A fundamental question first; what does a paint surface need to be protected from after all we should ascertain what we are trying to protect against.
• Ash – from forest fires or volcanic activity can produce an ash cloud that will settle on a paint surface. Ash is both abrasive (pumice or wood shards) and acidic when mixed with moisture. Forest fire ash is often caused by a firestorm, which is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires
• Acid rain (sulphur dioxide plus moisture) and is caused by sulphur from impurities in fossil fuels and nitrogen from the air combining with oxygen to form sulphur dioxide and nitrogen dioxide. These diffuse into the atmosphere and react with water to form sulphuric and nitric acids which are soluble and fall with the rain. Some hydrochloric acid is also formed. Occasional readings in rain and fog water have resulted in a pH level below 2.5 in some industrialized areas.
For neutralizing acidic type damage (acid rain, water spots, industrial fallout, for example) then ValuGard’s decontamination system is a really great choice.
• Artillery Fungus -the spots resemble asphalt (tar) spots but could be the spore of artillery fungus they look very much like tar spots and are usually about 1/10th-inch in diameter, typically artillery fungus feels like a sticky film, and when flattened can be smeared appearing white. It is a fungus that lives in wood-based mulch, the spores are usually shot only a short distance (several feet) but the wind can carry them for longer distances.
• Bird and Insect Excrement - comprises; Ammonia and urine as white crystals of uric acid (pH 3.0 - 4.5) a small organic compound, which is produced by the breakdown of protein during digestion, and is excreted by reptiles and birds. Uric acid is also the end product of nitrogen catabolism in birds Ammonia is a mixture of nitrogen gas and hydrogen gas; with moisture as a catalyst it becomes Ammonium Hydroxide, which is caustic.
• Brake Dust (FeO) - produced from the friction of brake pad material (semi-metallic, carbon resins, asbestos or ceramics formulations) rubbing against the rotor. The brake material friction as well as metal particles from the rotor disperses tiny particles of black ferrous oxide dust, which forms a cohesive bond to the wheels and adheres to localized paint surfaces. Ferrous oxide
microsized particles that come into contact with moisture will form rust that permeates deep into the paint's sublayers. This is a gradual process that often shows up as tiny red dots or rust spots n the paint surface, the corrosive damage caused is often not evident until it's too late.
microsized particles that come into contact with moisture will form rust that permeates deep into the paint's sublayers. This is a gradual process that often shows up as tiny red dots or rust spots n the paint surface, the corrosive damage caused is often not evident until it's too late.
• Bituminous Asphalt (Tar) -
the term asphalt is often used as an abbreviation for asphalt concrete, asphalt refers to a mixture of mineral aggregate and bitumen (tarmac) Composed almost entirely of bitumen, which is a category of organic liquids that are highly viscous, black, sticky and wholly soluble in carbon disulfide, mostly made up of highly condensed polycyclic aromatic hydrocarbons
• Bug Residue and Carcasses - the carcass is very acidic, and if left for any length of time will cause the porous clear coat to occlude (a non-transparent ‘clouded’ area) or may cause etching (a depression in the paint or glass surfaces) their exoskeletons will also scratch the paint surface
• Calcium (Ca) - an untimely lawn sprinkler, a springtime shower, or spots that remained after washing, the minerals are white calcium/sodium deposits that are alkaline-based, especially from hard water. If left on the vehicle paint surface they act the same way as acid rain in that they will etch the paint film surface.
• Contaminants - particles of dirt, grime, carbon emissions from catalytic converters, bird excrement, calcium, tar, oil, hard water deposits, calcium or any pollutant type substance that adheres to your paint surface, sometimes invisible the naked eye.
• Corrosion (metal oxidation) - Salt water conducts electricity better than fresh water so in areas that use salt on the roads, this process is greatly accelerated. Corrosion (rust) destroys metal by an electro-chemical reaction with water as the catalyst (water + ozone (an oxidizer) moisture + oxygen).
• Detergents (Harsh) - They are usually a blend of several surfactants, which are two opposing polar groups, hydrophilic and a non-polar group lipophilic. Surfactants use emulsification to dissolve and encapsulate oily particles. Paint surface protection (wax, polymers, coatings, etc) are formulated to be detergent resistant, but be cognizant that the harsh high alkaline detergents used in high street carwash, especially no-touch tunnel wash will strip away a large percentage of wax and a percentage of polymer sealant, leaving the sacrificial barrier compromised
• Exhaust Gas Emissions- the exhaust gases which are discharged from the engine contain several constituents that are harmful to human health and to the environment. Carbon monoxide (CO), hydrocarbons (HC), and aldehydes are generated in the exhaust as the result of incomplete combustion of fuel.
A significant portion of exhaust hydrocarbons is also derived from the engine lube oil. Hydrocarbons also have a negative environmental effect, being an important component of smog.
• Hydrazine - an extremely active acid that is found in jet fuel, vehicles that park in close proximity to airports or flight-paths are subject to this contaminant. Park near idling diesels or an airport with a lot of jet fuel exhaust in the air; kerosene strips waxes or sealant; diesel and jet fuels are refined kerosene.
• Infrared Radiation (IR) - represents part of the ultra violet solar spectrum (approximately 55%-60%). The remaining heat source comes from visible and ultra violet light Infrared radiation (IR) infrared radiation is a light source that transmits heat that will cause oxidation by drying out materials, like the paint (binder) resin system, the plasticizers in vinyl, moisture evaporation of leather and the elasticity of rubber causing these materials to dry out and become brittle and compromise their structural integrity. Ordinary auto window glass filters out about 35% of IR radiation.
• Industrial Fallout (IFO) - emissions from power generation, manufacturing plants and combustion engines emit Sulphuric acid from their exhaust stacks etc, vehicular catalytic converters emit carbon compounds that mixed with ozone (an oxidizer) and water becomes Sulphuric acid. Nitric oxide is an additional IFO component especially around Paper Mills.
When these pollutants alight on a surface they are neutral; forming a dry concentrate of acid (a dioxide, or dry substance of the compound). Water is added in the form of morning dew, fog, smog or rainwater, which contains two hydrogen atoms, and an oxygen atom. Oxygen is an oxidizer, ozone is an allotropic form of oxygen, and an oxidizer is any component that emits oxygen; many chemical compounds react to slight heating and an oxidizing process.
So now you have an acid + water +oxygen + ozone all of which equates to a highly concentrated acidic solution, which causes a concave indentation on the paint surface (the misnamed ‘water spots’) (See also Reactivity) Information resource- U.S. Environmental Protection Agency (EPA) website
• Oxidation - (reduction) - is caused by environmental pollutants (acid rain, ozone, industrial pollutants, hydrocarbons, etc)t UV- B radiation is known to contribute to the chemical modification of exposed paint surfaces resulting in loss of gloss, colour change, chalking, flaking and eventually destruction of the paint film. Inclement weather or the use of harsh detergents in commercial car washes using strong detergents will leach out the oils in the paint and dull the paint film surface even faster
It starts as a chemical reaction that causes the paint film surface to overheat, dry out and oxidize leaving microscopic surface imperfections and micro pores in the paint film surface that are vulnerable to deterioration.
• Ozone - when the air temperature reaches high 90 – 100.0F, plants and trees, which normally give off relatively small amounts of isoprene, started to produce greatly increased amounts. It is thought that isoprene, which is released by deciduous trees, and turpene, which is emitted by evergreen trees, help protect leaves from heat and sun damage.
In the atmosphere isoprene and turpene act as catalysts, increasing the rate at which sunlight breaks down nitrogen oxide - a car pollutant - into ozone. The more isoprene and turpene there is the more ozone is produced from smaller amounts of nitrogen oxide.
• Pollen - the yellow fines to coarse powders you see in the air is made up of small sperm cells from blooming plants and is one of the most common allergy triggers. The pollen from trees are the main concern, vehicles get hit with pollen laced trees that include: oak, western red cedar, elm, birch, ash, hickory, polar, sycamore, maple, cypress and walnut (which also leaves an oily residue). Pollen grains of pines, firs, and spruces are winged.
• Rain - liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Clean rain and 'as pure as driven snow are both things from a non-industrialized past, before (acid rain, hydrazine (airports) and industrial fallout (IFO)
Emissions from power generation, manufacturing plants and combustion engines emit Sulphuric acid from their exhaust stacks etc, vehicular catalytic converters emit carbon compounds that mixed with ozone (an oxidizer) and water becomes Sulphuric acid. Nitric oxide is an additional IFO component especially around Paper Mills.
The pH of rain varies, especially due to its origin. The US east coast, rain that is derived from the Atlantic Ocean has been typically recorded at a pH of ~ 5.0; rain that comes across the continental from the west has a pH of 3.5-5.0; and local thunderstorms can have a pH as low as 2.0. Rain becomes acidic primarily due to the presence of two strong acids, sulphuric acid (H2SO4) and nitric acid (HNO3). Sulphuric acid is derived from natural sources such as volcanoes, and wetlands (sulphate reducing bacteria); and anthropogenic sources such as the combustion of fossil fuels, and mining where H2S is present.
Nitric acid is produced by natural sources such as lightning, soil bacteria, and natural fires; while also produced anthropogenically by the combustion of fossil fuels and from power plants. In the past 20 years the concentrations of nitric and sulphuric acid has decreased in presence of rainwater, which may be due to the significant increase in ammonium (most likely as ammonia from livestock production), which acts as a buffer in acid rain and raising the pH
Sediment precipitation is a weather condition that occurs when a mix of rain and sediment (usually as dust or sand) fall from the sky as precipitation. It usually occurs in arid desert regions such as west Texas or Arizona
• Road Salt - Although salt is inert when subjected to freezing (15 – 20.oF ) it’s considered the lower limit for salt to melt snow/ice but once H2O, even in the form of moist air (i.e. humidity) is added the freezing point is lowered and the saline solution(salt/water) will have an adverse effect on the vehicles paint and undercarriage.
When washing the vehicle ensure that all salt is removed to avoid a saline solution remaining on the paint finish. Using a durable protection (Collinite Insulator Wax) will provide a sacrificial and renewable protection to the vehicles paint finish.
• Rail Dust - ferrous oxide (FeO) a dark colored powder that is created by railroad wheels abrading the metal tracks, these small particles become airborne and are sintered to the paint film surfaces. New cars that are transported by rail are at extra risk. When moisture combines with the oxide particles it creates small rust spots.
• Road Traffic Film-when rain and surface water washes away all the water soluble components of traffic film contaminants, what remains are the non-water soluble parts on the vehicle’s paintwork. Most of the micro particulates are either ferrous metal-when rain and surface water washes away all the water soluble components of traffic film contaminants, what remains are the non-water soluble parts on the vehicle’s paintwork.
RTF comprises, amongst other things, transmission oils, and other motor fluids as well as any dirt/grit deposits, including ferrous iron (from brake rotors) and anything else that is deposited on a cars paint surfaces and washed off by rain, as well as any fluids in the storm drain gutters. All these deposits alight on a road surface until it rains and is redistributed in the form of a spray from road wheels, hence road traffic film, when this emulsion settles on a paint surface
Washing your car will remove most accumulated soiling, but normal car washing won't remove road traffic film (RTF). Auto paint is porous and this film will permeate and cause the paint to become opaque, dulling the colour. Many RTF removers are either highly alkaline or contain aggressive solvents
The least intrusive method to remove RTF is by using a chemical paint cleaner, something like a d-limonene solvent / detergent (P21S® Paintwork Cleanse) or for more stubborn staining Swissvax Cleaner Fluid - Cleaner or Strong, which will remove any road film that normal car washing cannot
• Sand - dust storms arise when a gust front or other strong wind blows loose sand and dust from a dry surface. Particles are transported by suspension, causing soil erosion from one place and deposition in another; it will also erode a paint surface. The Sahara and dry lands around the Arabian Peninsula are the main terrestrial sources of airborne dust, with some contributions from Iran, Pakistan and India into the Arabian Sea, and China's significant storms deposit dust in the Pacific and sometimes much further afield.
A major dust storm swept through the southern portion of the Desert Southwest U.S. State of Arizona in 2011. The dust storm was triggered from thunderstorms to the south of the Phoenix metropolitan area. Dust from the deserts was blown up by high winds. The winds were estimated to be over 60 miles per hour and caused low visibility.
• Ultra violet radiation – (UV) light radiation is a paint film surface's greatest enemy, causing more damage than any other airborne contaminant and affecting both the interior and exterior of a vehicle.
The light in this spectral range is responsible for photo degradation. Photo degradation results in discoloration, fading, embitterment, cracking, chalking and/or loss of mechanical properties. Ordinary auto window glass filters out about 95% of UV radiation.
• Tree resin (sap) - appears like a dark brown/ rust red colour raised surface mark, some of the most common resinous tree sap types are: White Pine, Ponderosa Pine, Walnut (also secretes an oily residue) Maple, Oak, Popular, and Blue Spruce, none of which are water soluble, the acidic content of the sap will etch the paint surface; causing a concave surface.
• Water - beading that is left to evaporate on a car will lead to water marks; a standard household supply usually contains alkali minerals like calcium(Ca) magnesium (Mg), which are inert until heat and moisture is added and then it become corrosive. Once these form a ‘bead’ and they dry they will cause etching (a shallow indentation) of the paint surface. Clean rainwater (See also Acid Rain) has no harmful effects. The average unprotected water-based paint absorbs approximately a pint of water; dependent upon its content this may be harmful.
• Water Marks (Water Spots) - the misnomer ‘water spots’ are likely to contain the atmospheric pollutants nitrogen oxide from motor exhaust emissions and sulphur oxide emissions from chemical plants, paper making and refineries, all of which can cause paint discoloration, surface etching and leaving microscopic surface imperfections and micro pores in the paint film surface that are vulnerable to deterioration, which should be removed and naturalized as soon as possible.
These spots are recognizable by white or chalky rings that make the paint appear cloudy. Acid (acid rain, industrial fallout (IFO) hard water minerals (calcium and magnesium) alkali (from a sprinkler system) and of the above when mixed with moisture and heat (reactivity) will cause etching ((a concave circular mark and pitting)) each time moisture and heat are added the acid / alkali is reactivated and it permeates further into the paint surface, if left for too long they can become too deeply ingrained in the clear coat for ‘safe’ removal.
If not removed, these minerals can permanently etch paint and glass. Quick detailers typically contain a wax or polymer and water, using them on an acid / alkali will lock the acid, allowing it to react with moisture and heat, which makes the acid more aggressive
Reactivity
[: acceleration of a chemical reaction by a catalyst]
Be cognizant that an acid is inert until it comes into contact with moisture; like ike any chemical attacking a surface, temperature will dictate reactivity (acceleration of a chemical reaction by a catalyst [moisture and heat]. The more heat and moisture that is present (in the form of high humidity, dew and etc) the more aggressive the acid becomes.
Then you have; an acid + water +oxygen + ozone all of which forms an acidic oxygen molecule that causes a concave indentation (acid etching) to the paint surface it should be noted that until this acid is neutralised subsequent moisture and heat will reactivate the acid and allow further damage, as acid requires an alkaline to neutralize it
This will cause surface etching (an indentation of the clear coat) so they should be removed without delay. In this case, paint care not only serves aesthetics, but also helps preserve the vehicles. At lower temperatures (> 40.oF or less) there’s no reactivity and therefore little or no etching.
Sacrificial Protection
Sacrificial [: designed to be used up or destroyed]
A paint or metal surfaces natural sacrificial protection is oxidation; the so-called white rust on aluminium is in fact oxidation. Eventually, any mechanical abrasive action will wear away the oxidation; this could be caused by washing the paint surface, using a car duster, placing or removing a car cover, etc.
The micro-thin layer of wax or polymer sealant, apart from their aesthetic qualities provides a film that resists the adhesion of dirt and etc and allow you to wash the paint surface without using undue pressure, thereby micro marring the paint.
The latest nanotechnology coating or PPG CeramiClear™ Clear Coat although they are highly resistant to chemicals, detergents, scratches and ultra violet radiation (UV) will only offer limited resistance to acid etching from environmental contaminates. The newer nanotechnology coatings are better than conventional last step products (LSP) i.e. Silica coating.
Carnauba wax forms a multi-strata matrix, whereas a polymer is a mono layer that cross-links and forms a chain-like structure that forms a molecular bond to the paint surface. Contaminants will be further removed from the surfaces that are protected with a Carnaubas multi-strata matrix than with polymers mono (single) layer
Wax coatings act as a sacrificial buffer between a paint surface and the elements; these coatings are gradually used up (hence sacrificial) and reach a point where they can no longer protect; when they reach this point they must be renewed. Once attacked by acid (acid rain, Bird or Insect excrement, Industrial fallout, and etc) it should be removed and a fresh coating applied.
They are all forms of environmental contamination and given the right catalyst; reactivity (heat) plus moisture, they will become acidic. During this process the metal absorbs oxygen from the water and forms iron oxide (rust). Given the porosity of paint they permeate the paint matrix, causing erosion down to body metal.
Many natural and synthetic materials are attacked by ultra-violet radiation and products made using these materials may crack or disintegrate. This problem is known as ultra violet degradation, and is a common problem in materials that are exposed to sunlight.
UV Radiation Protection Provided by Auto Glass
Glass tinting and UV film protection are important ways to reduce exposure to UV radiation, which are the primary focus of the glass tinting and film tinting industry.
While a car provides substantial shading, the glass areas do not block UV. And, as it is not uncommon to spend several hours a day in a car, the implications for skin problems are high. Further, damage to eyes from glare and direct UV increases the more people drive.
American federal laws on auto glass are based on visible light transmission. They allow only for a vehicle's driver side and passenger side windows to be tinted up to 70% visual light transmission (VLT), which is also the normal factory tint found on most new cars. The focus on visible light transmission is driven by safety issues. The tint can be reflective which is dangerous to other drivers and/or can be dark to see through at night. If you do tint your car windows, you want to minimize UV transmission through the glass while allowing 70% or more visible light transmission.
Modern cars are being designed with inherent protection features, ordinary car window glass filters out about 97% of the (UV-B) radiation, the cause of photosynthesis (fading) and approximately 37% of (UV-IR) infra red (heat) radiation, modern clear coat paint also contains UV inhibitors.
Most automotive ultra violet (UV) absorbers are very durable and exhibit a 5 year half life, meaning that every five years the concentration is reduced by 50% percent.
New car owners mistakenly believe their new vehicle cannot be damaged by sun exposure. Due to the ozone layer depletion (global warming) in our atmosphere, UV radiation strength is increasing. Protecting your vehicle from UV radiation damage continues to be a very important.
An organic wax, contrary to popular opinion, or marketing, does not contain natural UV protection; the wax protects the leaves due to its thickness and the fact that it’s opaque. It does, however, provide a sacrificial surface that will resist acid (salt brine, bird excrement, acidic rain, etc) better than a polymer, which forms a molecular bond with the paint, whereas organic wax forms a semi-hard protective shell (although it lacks durability)
Protection from Environmental Contaminants
The following are things you can do to provide protection-
• Use a polymer paint sealant product on your car several times each year. A carnauba wax, contrary to popular myth (or is it marketing BS) does not contain inbuilt natural UV protection, this component must be added. . This sacrificial protections effectiveness lasts for no more than 2-3 months.
• For long-term paint protection use a coating (Opti-Coat™) its effectiveness lasts for 2-3 years
• Use a vinyl and rubber protectant with UV inhibitors on all exterior vinyl and rubber twice a month.
• Protect fabric and leather upholstery and carpet (especially in a roadster) with a UV and stain blocker treatment twice a year.
• Use a sun shield in your windshield when parked outside.
• Cover your car when parked outside for extended periods.
These simple measures will ensure your vehicle's appearance has a chance of remaining in excellent condition for ten or more years. If you take no precautions, its appearance will noticeably deteriorate in less than five years
If you need advice on how to remove any of the above environmental contaminates send me a PM or ask your question either here or in the main forum. The main article “Environmental Pollutants” is just too large to post (35,000 words / 34 pages)
Over Polishing Paint
Polishing alleviates a myriad of paint surface problems. But use abrasive polishes wisely to maintain paint condition and to resolve surface damage problems. But know when to seek alternative methods of damage control and avoid over-polishing with harsh, abrasive polishes.
Copyright © 2000 by Jon Miller, all rights reserved.
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