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With Chris Curwen & Expert Auto Painter - Dave Gage (Car Cosmetics)

May 1st, 2007 - Issue 01

In this issue:

    * How to Reduce Pollution when Spray Painting a Vehicle.

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It is clear to us all that our planet is becoming more and more polluted over time and this has propelled various government agencies and research institutions to start taking the necessary steps to reduce the amount of new pollution as well as reduce the amount we already have in the environment.

The automotive paint industry is a field of concern because of the methods of applying automotive paint and has had to abide by these same emission standards.

If automotive paint was applied by a brush or roller then the level of concern wouldn't be as apparent.

However by thinning paint by the use of solvents, making it possible for it to be sprayed onto surfaces easily, allows for a great deal of these harmful solvents to escape into the atmosphere not only from paint overspray but also from solvent evaporation (after paint is sprayed, the solvents must evaporate so that the paint can dry and solidify).

Lacquer paints contain lacquer thinner and enamel paints as well and urethanes contain reducers. You may be surprised to read that any gallon of paint can contain anything up to 90% solvent!

Unfortunately the types of solvents used in automotive paints are composed of volatile (evaporate easily) organic compounds (VOCs).

The types of organic compounds in traditional auto paint solvents react with other molecules in the air such as nitrous oxides resulting in the production of ozone, ozone being one of the main causes of smog.

To comply with government regulations, body shops use high-tech paint booths complete with downdraft ventilation systems. Each booth must be equipped with special filtering systems that will burn off or filter out the VOC's.

Government agencies, auto paint manufacturers, auto painters and paint equipment companies have addressed the problem of VOC's, paint overspray and material waste as contributing factors to atmospheric pollution and are therefore currently looking for a solution to this pollution problem.

One effective solution to help reduce the amount of VOC and paint overspray pollution significantly involves using a high volume spray with low pressure, referred to as High Volume Low Pressure (HVLP).

This process results in more paint sticking to the vehicles body and less overspray than conventional spray paint systems. In principle, with more of the materials sticking to the sheet metal surface, less is released into the atmosphere.

The early HVLP spray paint systems incorporated a turbine system that replaced the conventional air compressor. This concept wasn't widely accepted thanks to the turbine system causing the air pushing the paint onto the vehicle to be too hot. The result was the paint dried too fast.

A better solution was to develop a HVLP spray paint gun to use in conjunction with a conventional air compressor. The concept was familiar to experienced painters. It also justified purchasing an air compressor for the novice.

HVLP works by increasing the amount or volume of paint that can pass evenly through the spray gun's ports and nozzle. This means a low amount of pressure is only needed to propel the paint material.

The result is paint being given a better chance at sticking to the surface of the vehicle and up to 50% less material being wasted as overspray. Since the cost of paint material is expensive, a quality HVLP spray gun will more than pay for itself in just a few paint jobs.

This reduction in overspray is very important to any part-time auto painter who is working out of his home garage or workshop.

It is recommended that a HVLP spray gun has an air pressure of 10 psi at its tip. Don't confuse this with the air pressure at the inlet of the spray gun where the hose connects. The inlet pressure may sometimes need to be near 60 psi to obtain the right tip pressure; this will of course depend on the design of the spray gun.

A spray gun may be classified as siphon feed or gravity feed in addition to being either a conventional or HVLP model. A siphon fed gun has a paint cup that is mounted below the air nozzle. The design requires more air pressure in order to get the paint out of the cup.

A gravity fed spray gun has a paint cup that is mounted above the air nozzle to allow gravity to do some of the work for the air pressure. The result is that a lower inlet of air pressure is required.

Paint manufacturers are always looking for ways to develop new paint products to reduce the amount of VOC's entering the atmosphere.

Waterborne paint products are in the works for this very reason, using water to transfer the paint through the gun onto the car reduces the need for solvents that contain VOC's, however these types of paint products are still not widely used for a variety of reasons.

Durability issues remain. Paint manufacturers are working hard to develop automotive paints that can be mixed with water for spraying and that have the durability needed for the final top coat.

Many of today's cars have a waterborne color coat but it is covered with a solvent borne enamel clear coat for added durability.

Waterborne paints are also sensitive to humidity during their application. Humidity controlled spray booths had to be used and carefully controlled when spraying the first waterborne paints.

To ensure you are fully aware of the regulations at all times, stay in contact with your local auto body paint and supply store. The staff will get to know quickly about important changes that have taken place in regard to industry standards.

They will also have access to the most current information sheets on the various paint products, materials and compatible systems, including those for older vehicles in need of touch up.

For your benefit, the manufacturers of most paint products are responsible for making their products environmentally safe as well as user-friendly. The manufacturers of such products continually work to reduce the amount of VOC's in the various products.

There is not a lot that you can personally do to reduce the amount of VOC's in the actual paint itself, it is very important therefore that you follow the laws regarding the proper use and disposal of these products.

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That's all we have for you this week. Thank you very much for reading. We both hope this issue has been of valued interest to you.

Next week we'll cover more on HVLP and include a new topic.

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com