Spray painting
Encyclopedia
Spray painting is a painting
technique where a device sprays a coating (paint, ink, varnish, etc.) through the air onto a surface. The most common types employ compressed gas—usually air
—to atomize and direct the paint particles. Spray guns evolved from airbrush
es, and the two are usually distinguished by their size and the size of the spray pattern they produce. Airbrushes are hand-held and used instead of a brush for detailed work such as photo retouching, painting nails or fine art. Air gun spraying uses equipment that is generally larger. It is typically used for covering large surfaces with an even coating of liquid. Spray guns can be either automated or hand-held and have interchangeable heads to allow for different spray patterns. Single color aerosol paint
cans are portable and easy to store.
is generally credited with the invention of spray painting. In 1892, working under extremely tight deadlines to complete construction of the World's Columbian Exposition
, Daniel Burnham
appointed Millet to replace the fair's official director of color, William Pretyman. Pretyman had resigned following a dispute with Burnham. After experimenting, Millet settled on a mix of oil and white lead that could be applied using a hose and special nozzle, which would take considerably less time than traditional brush painting.
In 1949, Edward Seymour developed spray paint that could be delivered from an aerosol can.
Due to a wide range of nozzle shapes and sizes, the consistency of the paint can be varied. The shape of the workpiece and the desired paint consistency and pattern are important factors when choosing a nozzle. The three most common nozzles are the full cone, hollow cone, and flat stream.
There are two types of air-gun spraying processes. In a manual operation method the air-gun sprayer is held by a skilled operator, about 6 to 10 in (15.2 to 25.4 cm) from the object, and moved back and forth over the surface, each stroke overlapping the previous to ensure a continuous coat. In an automatic process the gun head is attached to a mounting block and delivers the stream of paint from that position.
The object being painted is usually placed on rollers or a turntable to ensure overall equal coverage of all sides.
, materials consumption, and air pollution.
A regulator is often required so that the air pressure from a conventional compressor can be lowered for the HVLP spray gun. Alternatively a turbine unit (commonly containing a vacuum cleaner derived motor) can be used to propel the air without the need for an air line.
A rule of thumb puts two thirds of the coating on the substrate and one third in the air. True HVLP guns use 8–20 cfm (13.6–34 m3/hr), and an industrial compressor with a minimum of 5 hp output is required. HVLP spray systems are used in the automotive, marine, architectural coating, furniture finishing, scenic painting and cosmetic industries.
, the atomized particles are made to be electrically charged, thereby repelling each other and spreading themselves evenly as they exit the spray nozzle. The object being painted is charged oppositely or grounded. The paint is then attracted to the object giving a more even coat than wet spray painting, and also increasing the percentage of paint that sticks to the object. This method also means that paint covers hard to reach areas. The whole is then baked to properly attach the paint: the powder turns into a type of plastic. Car body panels and bike frames are two examples where electrostatic spray painting is often used.
There are three main technologies for charging the fluid (liquid or powders):
The fluid pressure is provided by an airless pump, which allows much heavier materials to be sprayed than is possible with an airspray gun. Compressed air is introduced into the spray from an airless tip (nozzle) to improve the fineness of atomisation. Some electric airless sprayers are fitted with a compressor to allow the use of an air assisted airless gun in situations where portability is important.
Advantages of airless spray are:
Most coatings can be sprayed with very little thinner added, thereby reducing drying time and decreasing the release of solvent into the environment.
Care must be used when operating, as airless spray guns can cause serious injury, such as injection injuries, due to the paint ejecting from the nozzle at high pressure.
These machines are commonly used to apply stain, sealer, and lacquer. They can apply water- or solvent-based coatings. In recent years ultraviolet-cured coatings have become commonplace in profile finishing, and there are machines particularly suited to this type of coating.
http://www.chinapaintsprayer.net
controlled closed environment, used to paint vehicles in a body shop
. To ensure the ideal working conditions (temperature
, air flow and humidity
), these environments are equipped with one or more groups of ventilation
, consisting of one or more motors
and one or more burners to heat the air blown.
. The introduction of inexpensive and portable aerosol paint
has been a boon to this art form, which has spread all over the world. Spray painting has also been used in fine art
. Jules Olitski
, Dan Christensen
, Peter Reginato
, Sir Anthony Caro, and Jean-Michel Basquiat
have used airbrush
es, for both painting
and sculpture
.
Painting
Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...
technique where a device sprays a coating (paint, ink, varnish, etc.) through the air onto a surface. The most common types employ compressed gas—usually air
Air compressor
An air compressor is a device that converts power into kinetic energy by compressing and pressurizing air, which, on command, can be released in quick bursts...
—to atomize and direct the paint particles. Spray guns evolved from airbrush
Airbrush
An airbrush is a small, air-operated tool that sprays various media including ink and dye, but most often paint by a process of nebulization. Spray guns developed from the airbrush and are still considered a type of airbrush.-History:...
es, and the two are usually distinguished by their size and the size of the spray pattern they produce. Airbrushes are hand-held and used instead of a brush for detailed work such as photo retouching, painting nails or fine art. Air gun spraying uses equipment that is generally larger. It is typically used for covering large surfaces with an even coating of liquid. Spray guns can be either automated or hand-held and have interchangeable heads to allow for different spray patterns. Single color aerosol paint
Aerosol paint
Aerosol paint is a type of paint that comes in a sealed pressurized container and is released in a fine spray mist when depressing a valve button. A form of spray painting, aerosol paint leaves a smooth, evenly coated surface, unlike many rolled or brushed paints. Standard sized cans are portable,...
cans are portable and easy to store.
History
Francis Davis MilletFrancis Davis Millet
Francis Davis Millet was an American painter, sculptor, and writer who died in the sinking of the on April 15, 1912.-Early life:Francis Davis Millet was born in Mattapoisett, Massachusetts...
is generally credited with the invention of spray painting. In 1892, working under extremely tight deadlines to complete construction of the World's Columbian Exposition
World's Columbian Exposition
The World's Columbian Exposition was a World's Fair held in Chicago in 1893 to celebrate the 400th anniversary of Christopher Columbus's arrival in the New World in 1492. Chicago bested New York City; Washington, D.C.; and St...
, Daniel Burnham
Daniel Burnham
Daniel Hudson Burnham, FAIA was an American architect and urban planner. He was the Director of Works for the World's Columbian Exposition in Chicago. He took a leading role in the creation of master plans for the development of a number of cities, including Chicago and downtown Washington DC...
appointed Millet to replace the fair's official director of color, William Pretyman. Pretyman had resigned following a dispute with Burnham. After experimenting, Millet settled on a mix of oil and white lead that could be applied using a hose and special nozzle, which would take considerably less time than traditional brush painting.
In 1949, Edward Seymour developed spray paint that could be delivered from an aerosol can.
Air gun spraying
This process occurs when paint is applied to an object through the use of an air-pressurized spray gun. The air gun has a nozzle, paint basin, and air compressor. When the trigger is pressed the paint mixes with the compressed air stream and is released in a fine spray.There are two types of air-gun spraying processes. In a manual operation method the air-gun sprayer is held by a skilled operator, about 6 to 10 in (15.2 to 25.4 cm) from the object, and moved back and forth over the surface, each stroke overlapping the previous to ensure a continuous coat. In an automatic process the gun head is attached to a mounting block and delivers the stream of paint from that position.
The object being painted is usually placed on rollers or a turntable to ensure overall equal coverage of all sides.
HVLP (High Volume Low Pressure)
This is similar to a conventional spray gun using a compressor to supply the air, but the spray gun itself requires a lower pressure (LP). A higher volume (HV) of air is used to aerosolise and propel the paint at lower air pressure. The result is a higher proportion of paint reaching the target surface with reduced oversprayOverspray
Overspray refers to the application of any form of paint, varnish, stain or other non-water soluble airborne particulate material onto an unintended location...
, materials consumption, and air pollution.
A regulator is often required so that the air pressure from a conventional compressor can be lowered for the HVLP spray gun. Alternatively a turbine unit (commonly containing a vacuum cleaner derived motor) can be used to propel the air without the need for an air line.
A rule of thumb puts two thirds of the coating on the substrate and one third in the air. True HVLP guns use 8–20 cfm (13.6–34 m3/hr), and an industrial compressor with a minimum of 5 hp output is required. HVLP spray systems are used in the automotive, marine, architectural coating, furniture finishing, scenic painting and cosmetic industries.
LVLP (Low Volume Low Pressure)
Like HVLP, these spray guns also operate at a lower pressure (LP), but they use a low volume (LV) of air when compared to conventional and HVLP equipment. This is a further effort at increasing the transfer efficiency (amount of coating that ends up on the target surface) of spray guns, while decreasing the amount of compressed air consumption.Electrostatic spray painting
In electrostatic spray painting or powder coatingPowder coating
thumb|right|Aluminium extrusions being powder coatedPowder coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler...
, the atomized particles are made to be electrically charged, thereby repelling each other and spreading themselves evenly as they exit the spray nozzle. The object being painted is charged oppositely or grounded. The paint is then attracted to the object giving a more even coat than wet spray painting, and also increasing the percentage of paint that sticks to the object. This method also means that paint covers hard to reach areas. The whole is then baked to properly attach the paint: the powder turns into a type of plastic. Car body panels and bike frames are two examples where electrostatic spray painting is often used.
There are three main technologies for charging the fluid (liquid or powders):
- Direct charging: An electrode is immersed in the paint supply reservoir or in the paint supply conduit.
- Tribo charging: This uses the friction of the fluid which is forced through the barrel of the paint gun. It rubs against the side of the barrel and builds up an electrostatic charge.
- Post-atomization charging: The atomized fluid comes into contact with an electrostatic field downstream of the outlet nozzle. The electrostatic field may be created by electrostatic inductionElectrostatic inductionElectrostatic induction is a redistribution of electrical charge in an object, caused by the influence of nearby charges. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators, such as the Wimshurst machine, the...
or coronaCorona dischargeIn electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor that is electrically energized...
, or by one or more electrodes (electrode ring, mesh or grid).
Rotational bell
With this method the paint is flung into the air by a spinning metal disc ("bell"). The metal disc also imparts an electrical charge to the coating particle.Electric fan
There are a variety of hand-held paint sprayers that either combine the paint with air, or convert the paint to tiny droplets and accelerate these out of a nozzle.Hot spray
By heating the full bodied paint to 60-80 deg C, it is possible to apply a thicker coat. Originally the paint was recirculated, but this caused bodying up, the system was changed to direct heating on line. Hot spraying was also used with Airless and Electrostatic Airless to decrease bounce- back. Two pack materials usually had premix before tip systems using dual pumps.Air assisted airless spray guns
These use air pressure and fluid pressure 300 to 3000 psi (2,068,427.2 to 20,684,271.9 ) to achieve atomization of the coating. This equipment provides high transfer and increased application speed and is most often used with flat-line applications in factory finish shops.The fluid pressure is provided by an airless pump, which allows much heavier materials to be sprayed than is possible with an airspray gun. Compressed air is introduced into the spray from an airless tip (nozzle) to improve the fineness of atomisation. Some electric airless sprayers are fitted with a compressor to allow the use of an air assisted airless gun in situations where portability is important.
Airless spray guns
These operate connected to a high pressure pump commonly found using 300 to 7500 psi (2,068,427.2 to 51,710,679.7 ) pressure to atomize the coating, using different tip sizes to achieve desired atomization and spray pattern size. This type of system is used by contract painters to paint heavy duty industrial, chemical and marine coatings and linings.Advantages of airless spray are:
- The coating penetrates better into pits and crevices.
- A uniform thick coating is produced, reducing the number of coats required.
- A very "wet" coating is applied, ensuring good adhesion and flow-out.
Most coatings can be sprayed with very little thinner added, thereby reducing drying time and decreasing the release of solvent into the environment.
Care must be used when operating, as airless spray guns can cause serious injury, such as injection injuries, due to the paint ejecting from the nozzle at high pressure.
Automated linear spray systems
Manufacturers who mass-produce wood products use automated spray systems, allowing them to paint materials at a very high rate with a minimum of personnel. Automated spray systems usually incorporate a paint-saving system which recovers paint not applied to the products. Commonly, linear spray systems are for products which are laying flat on a conveyor belt and then fed into a linear spray system, where automated spray guns are stationed above. When the material is directly below the guns, the guns begin to paint the material. Materials consist of lineal parts usually less than 12 inches (30.5 cm) wide, such as window frames, wood moulding, baseboard, casing, trim stock and any other material that is simple in design.These machines are commonly used to apply stain, sealer, and lacquer. They can apply water- or solvent-based coatings. In recent years ultraviolet-cured coatings have become commonplace in profile finishing, and there are machines particularly suited to this type of coating.
http://www.chinapaintsprayer.net
Automated flatline spray systems
Mass produced material is loaded on a conveyor belt where it is fed into one of these flatline machines. Flatline machines are designed to specifically paint material that is less than 4 inches (10.2 cm) thick and complex in shape, for example a kitchen cabinet door or drawer front. Spray guns are aligned above the material and the guns are in motion in order to hit all the grooves of the material. The guns can be moved in a cycle, circle, or can be moved back and forth in order to apply paint evenly across the material. Flatline systems are typically large and can paint doors, kitchen cabinets, and other plastic or wooden products.Spray booth
A spray booth is a pressurePressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
controlled closed environment, used to paint vehicles in a body shop
Body shop
Body shopping is the practice of consultancy firms recruiting information technology workers in order to contract their services out on short-term bases...
. To ensure the ideal working conditions (temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, air flow and humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
), these environments are equipped with one or more groups of ventilation
Ventilation (architecture)
Ventilating is the process of "changing" or replacing air in any space to provide high indoor air quality...
, consisting of one or more motors
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
and one or more burners to heat the air blown.
Other Applications
One application of spray painting is graffitiGraffiti
Graffiti is the name for images or lettering scratched, scrawled, painted or marked in any manner on property....
. The introduction of inexpensive and portable aerosol paint
Aerosol paint
Aerosol paint is a type of paint that comes in a sealed pressurized container and is released in a fine spray mist when depressing a valve button. A form of spray painting, aerosol paint leaves a smooth, evenly coated surface, unlike many rolled or brushed paints. Standard sized cans are portable,...
has been a boon to this art form, which has spread all over the world. Spray painting has also been used in fine art
Fine art
Fine art or the fine arts encompass art forms developed primarily for aesthetics and/or concept rather than practical application. Art is often a synonym for fine art, as employed in the term "art gallery"....
. Jules Olitski
Jules Olitski
Jules Olitski was an American abstract painter, printmaker, and sculptor.-Early life:Olitski was born Jevel Demikovski in Snovsk, in the Russian SFSR , a few months after his father, a commissar, was executed by the Russian government...
, Dan Christensen
Dan Christensen
Dan Christensen, the American abstract painter, was born in Cozad, Nebraska on October 6, 1942, he died in Easthampton, New York on January 20, 2007....
, Peter Reginato
Peter Reginato
Peter Reginato , is an American abstract sculptor.Reginato was born in Dallas, Texas, but grew up in the hills outside Oakland, California and he attended the San Francisco Art Institute. He began making abstract sculpture in 1965 and moved to New York City in 1966 to pursue his career as a sculptor...
, Sir Anthony Caro, and Jean-Michel Basquiat
Jean-Michel Basquiat
Jean-Michel Basquiat was an American artist. His career in art began as a graffiti artist in New York City in the late 1970s, and in the 1980s produced Neo-expressionist painting.-Early life:...
have used airbrush
Airbrush
An airbrush is a small, air-operated tool that sprays various media including ink and dye, but most often paint by a process of nebulization. Spray guns developed from the airbrush and are still considered a type of airbrush.-History:...
es, for both painting
Painting
Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...
and sculpture
Sculpture
Sculpture is three-dimensional artwork created by shaping or combining hard materials—typically stone such as marble—or metal, glass, or wood. Softer materials can also be used, such as clay, textiles, plastics, polymers and softer metals...
.
See also
- Aerosol paintAerosol paintAerosol paint is a type of paint that comes in a sealed pressurized container and is released in a fine spray mist when depressing a valve button. A form of spray painting, aerosol paint leaves a smooth, evenly coated surface, unlike many rolled or brushed paints. Standard sized cans are portable,...
- AirbrushAirbrushAn airbrush is a small, air-operated tool that sprays various media including ink and dye, but most often paint by a process of nebulization. Spray guns developed from the airbrush and are still considered a type of airbrush.-History:...
- Frederick William LawrenceFrederick William LawrenceFrederick William Lawrence was a Canadian/American airbrush painter, and probably the father of realistic spray painting.Formerly an officer of the Royal Canadian Mounted Police , he served with the Canadian Army in World War I, where he was severely wounded. After months of hospitalisation, he...
- Huffing
- Primer (paint)Primer (paint)A primer is a preparatory coating put on materials before painting. Priming ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.-When primers are used:...
- Spray paint artSpray paint artSpray paint art is an art form using spray paint, traditionally on posterboard, but can be done on any non-porous material, such as wood, metal, glass, ceramic or plastic...
(graffiti)
More Spray Painting Resources
- Encyc: Spray paint
- Beginners Guide To Car Spray Painting & Cleaning - Car Paint and Bodywork Guide