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

October 16th, 2007 - Issue 25

In this issue:

• Basic Paint Ingredients (Paint Pigments, Binders and Paint Solvents).

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Automotive paint is made up of paint pigments, binders and paint solvents.

• Paint Pigments give paint material its color, whereas

• Binders are used to hold pigment materials together and keep them in a solid state that remains attached to vehicle bodies.

• Paint Solvents (thinners and reducers) transform solid pigment and binder materials into spray-able liquids and are for the most part, the materials that evaporate into the atmosphere and cause pollution concerns.

To discover how to reduce pollution when spray painting a vehicle please refer to our May, 1st on 'How to Reduce Pollution When Spray Painting a Vehicle'.

Various combinations of paint pigments, binders and paint solvents indeed produce different types of paint. These differences are reflected in coverage techniques, drying times, how easy it is to repair and durability.

In general, all paint materials are basically solid substances that have been mixed with a solvent, changing them into a liquid form so that they can be sprayed.

Once the paint solvents have evaporated, paint pigments and binders harden into a colorful medium that strongly adheres to auto body surfaces, offering attractive appearances and protection against rust for the underlying metal.

In the past, auto painters were limited to either straight enamel paint or lacquer paint.

• Enamel paint was relatively easy to apply and covered in just one or two coats. They did not have to be rubbed out and they had good durability.

• Lacquer paint on the other hand required many thin color base coats and numerous clear coats over the color bases, which then had to be rubbed out in order to gain a deep, lustrous, showroom shine.

Lacquer also dried fast and allowed minor flaws to be gently wet-sanded and then painted over just minutes after the paint was applied.

Advances in automotive paint chemistry have introduced new kinds of enamel paint and lacquer paint, referred to as acrylic paint. Acrylic simply means 'plastic'.

Although acrylic enamel and acrylic lacquer retain their same basic application and benefit characteristics, their durability and ultraviolet sunlight resistance have been greatly improved.

As acrylic enamels and lacquers underwent improvements, a new type was introduced: Urethane Paint.

Urethane paint products and more recently polyurethane, combined advantages of both enamel paint and lacquer paint to offer quick drying ingredients that could cover in one to three coats and could allow blemish repair soon after a coat was sprayed on.

In How to Paint a Car - Part 1 you can see the use of urethane paint being applied. As you will see from the film, it only takes 2-3 coats before the repair area is covered and ready for clear coat.

One of the biggest advantages urethane paint offers is DURABILITY. They were developed to resist the hazards of today's harsh airborne pollutants, acid rain and other oxidizing elements.

To confirm, although basic ingredients remain the same (paint pigments, binders and paint solvents) their chemical make-up gives paint its own individual characteristics.

The addition of chemical hardeners plays a significant role by improving the way paint pigments and binders bond together and adhere to painted surfaces.

Liquid hardeners or catalysts are added to paint and solvent mixtures in established proportions as recommended by label instructions and informational guidelines.

Instructions for hardeners as well as their labels and information sheets, emphasize that fresh air respirators must be employed whenever hardeners are used.

This is because hardeners contain isocyanate chemicals, which have been regarded as being a health hazard when inhaled or absorbed through the skin.

Currently, three basic types of automotive paint are being produced:

• Acrylic-Enamel

• Acrylic-Lacquer

• Urethane

The vast majority of automotive paint sales these days are urethane-based products. Any sales of acrylic enamel or acrylic lacquer are usually for restoration projects only.

Therefore, following this article, we strongly suggest that you use urethane paint products with a base coat clear coat system being the first choice over a single stage.

Here are the characteristics of a Base Coat Clear Coat Paint System:

• Base coat sprays like lacquer; can be sprayed anywhere.
• Base coat dries very quickly and can be sanded and resprayed.
• Base coat cannot be sanded without re-coating before applying clear coat.
• Most base coat drying time controlled by 'reactive reducer' must be matched to ambient temperatures, however this is not as critical as with lacquer.
• Shelf-life of 'reactive reducer' is short; cannot be checked without spray testing.
• Once mixed, paints must be sprayed, gun cleaned thoroughly, left overs disposed of safely, etc.
• Un-mixed left over paint products do not keep well.
• Mixing ratios for most paint products are critical.
• Clear coat should be sprayed in a booth however it can effectively be sprayed in a clean, bug-free, indoor, ventilated space such as a home workshop or garage.
• Clear coat requires proper spray technique; runs/fish eyes and also orange-peels easily.
• Runs/sags can often be color sanded out of clear.
• Dirt, bugs and other problems require respraying of base coat (can be spotted-in) and re-clearing.
• If sprayed correctly, clear dries smooth and very glossy (showroom shine) but is usually color sanded and rubbed out for the best finish.
• Clear coat is tough, ages well; but peels if left open to the elements.
• Can be repaired/spotted-in/touched up but requires several steps, increasing coverage area of each step (primer, base coat, clear coat)
• Base coat overspray is minimal, like lacquer; clear coat overspray is not readily visible, but leaves rough residue on surfaces.
  

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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.

COMING NEXT ISSUE: We cover in more detail: Modern-day Urethane Paint.

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com