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

August 14th, 2007 - Issue 16

In this issue:

• We conclude the series on Bodywork Repair and cover Preparing Fiberglass.
• We're going to make a start on getting back to automotive painting basics this week. So just what is Auto Painting?
• Questions & Answers: The first question this week comes from Ronald Divino and he asks:
  

'Please explain to me the difference between Acrylic Lacquer and Acrylic Enamel.'

Our second question comes from William Barth:

'Thanks for your expertise. I am learning a lot and I feel my project ('97 Ford F150 GT) will be a great success with your support.

However, I have painted a few work trucks and though my preparation work on the bodies has been thorough, my application of the paint has left me with a lot of wet sanding.

There has been pin hole like orange peel effect and even after wet sanding for hours on end I still get little pin holes. Most people don't see it but I can and it is unacceptable to me. I want my truck to be a show stopper! Thanks again, Bill.'

To repair damaged fiberglass you will need to use resin, catalyst and fiberglass matte products, unless your vehicle is made from a product called Fiber Reinforced Plastic (FRP).

Those vehicles will require specific repair materials that are unique to their physical make-up and to their chemical design.

There are auto body technicians who prefer to cover a finished fiberglass repair with a light coat of glazing putty to reduce the problem of air bubble induced pinholes.

Air bubbles in resin are a common hazard and pinholes found on the surface are sometimes impossible to avoid.

Unless you have to abide by any special product instructions, primer is mixed and applied to fiberglass repairs using the same method as for sheet metal surfaces.

You would then simply use 320- and 500-grit sandpaper to smooth down the surface.

After you have finished sanding the primer material, blow off any dust ideally using an air hose and then mask the car.

Masking about two feet in all directions will be sufficient as long as you maintain control when spraying the primer.

Use wax and grease remover to thoroughly clean the surface followed, if you wish, by a wipe down with an aerosol glass cleaner.

Wipe with a tack cloth and then spray the appropriate sealer. When you've reached the flash (drying) time, tack off the body again and paint.

To witness a professional demonstration of bodywork being repaired on a vehicle, please refer to 'How to Paint a Car - Part 1'.

Great...that concludes our series on Bodywork Repair.

Now let us move onto covering the basics of automotive painting. We both feel that by covering the basics we're going to be building the right foundations with all our subscribers.

The different ways that paint can be applied to an automotive body depends on the job in hand.

It is a well known fact that a new vehicle leaving the factory has a perfect coat of fresh paint. Over a period of time however, the appearance of a vehicle will start to diminish due to driving; this will cause minor scratches and other such problems to occur.

These commonly occurring problems are generally solved by touch-up work using a small brush from a bottle of touch-up paint used to apply the paint to the scratches and other nicks.

Likewise, paint from a spray can may close enough match the color and texture to refinish or modify a trim panel.

In the case that your vehicle has been involved in a collision, generally the repair work for the various damaged parts or sections would be carried out by using conventional spray guns.

If the entire vehicle is going to be repainted however, paint specifically meant for automotive refinishing should be used.

The techniques used to apply vehicle paint are decided by the amount and type of coverage needed and the current surface material condition.

For example, to touch-up a small scratch there is no need for a full size spray gun, conversely for an entire panel a touch-up brush would not be the most appropriate option.

So an understanding of the situation and common sense are required during the planning stages of any painting project.

To get optimum results from spray paint, aerosol can or otherwise, it's required that the spray-can be warm.

This will help with mixing the paint ingredients and give maximum power to the propellant.

Heating of the spray-can should be carried out as per guidelines given on the label and never over the recommended safety level. Whatever you do never heat a spray can directly over a flame.

If you need to warm the spray paint, you could allow it to sit in a sink of warm water prior to use.
 
Preparation plays a vital role in auto painting. To obtain a professionally and visually acceptable, compatible and durable paint job, it is required that you use products designed for the right purpose and that they suit the existing paint finishes and undercoat preparations.

A paint job will only be long lasting, if the various layers of body filler, primer, sealer and final top coat are compatible with one another.

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Questions & Answers

Ronald Divino asks:

'Please explain to me the difference between Acrylic Lacquer and Acrylic Enamel.'

Ans: No problem Ronald. For all intents and purposes, the use of lacquers and enamels in automotive painting is obsolete.

Alkyd (natural-based) and acrylic (plastic-based) enamels dry by evaporation of the reducers first and then by oxidation of the resin or binder.

The result here is that the paint finish may appear to dry quickly through evaporation of its solvent base however, the material continues to harden as resins combine with oxygen in the air.

This is why infrared lamps were used; the heat from them would speed up this process.

During this curing process, a dry synthetic film would solidify over the top of the finish to offer a tough, shiny color coat.

Wet sanding this coat to remove bits of dirt or debris would destroy that film and require touch-up painting to repair the surface blemishes.

When compared to the durability of Urethane products, alkyd and acrylic enamels fall way short.

Although they can cover in just one or two coats they cannot hold up to the same kind of harsh environments.

In addition, the application of any lacquer based product over enamel would result in surface wrinkling. This is because the materials in enamel cannot hold up to the strong chemicals in lacquer.

A special sealer had to be applied first to prevent lacquer solvents from penetrating and ruining enamel bases.

Acrylic Lacquer has been a favorite paint among auto enthusiasts for years.

It is easy to mix, can be applied at relatively low pressures, dries quickly and can generally be repaired and re-coated within 10 to 20 minutes after the last coat has been sprayed making it popular with custom car painters.

Lacquer requires a number of coats to achieve color and coverage expectations. Then coats of clear lacquer are sprayed over color bases for protection and for required buffing.

To buff lacquer color coats you would affect the color tint. This is why clear coats are applied so that buffing shines them to a showroom finish without disturbing the underlying color base.

Due to the amount of Volatile Organic Compounds (VOC's) emitted by lacquer solvents, regulatory agencies minimized the use of lacquer paint or required that it only be sprayed in down-draft paint spray booths equipped with special filters and air-purifying systems.

This is a factor to consider Donald if you're contemplating a complete paint job for your car.

If you are using Acrylic Enamel or Lacquer Donald then we recommend you consult an auto body paint a supply store member of staff for advice and recommendations that apply to your specific job.

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Our second question this week comes from William Barth:

'Thanks for your expertise. I am learning a lot and I feel my project ('97 Ford F150 GT) will be a great success with your support.

However, I have painted a few work trucks and though my preparation work on the bodies has been thorough, my application of the paint has left me with a lot of wet sanding.

There has been pin hole like orange peel effect and even after wet sanding for hours on end I still get little pin holes. Most people don't see it but I can and it is unacceptable to me. I want my truck to be a show stopper! Thanks again, Bill.'

Ans: Orange peel Bill is caused by a number of factors:

1. Paint was mixed and reduced incorrectly,
2. Spray gun was not set up properly (wrong tips and spray cap),
3. Adverse climatic conditions (Hot or Cold). The ideal temp to paint at is 22.5 degrees centigrade.

As for pinholes, this is usually caused by too much clear coat being applied, again 2-3 coats is all that should be required.

Specific lacquer and urethane paint finishes can be wet sanded and polished to remove nibs, flatten orange peel and smooth out blemishes.

This work is normally carried out on clear coats instead of on actual color coats and may require additional light applications of clear afterwards.

This is why professionals will rarely remove the masking from a vehicle until they are pleased with the entire paint job and are sure that they have taken care of all imperfections.

We hope this helps guys.

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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 'How you can determine the type of paint on your car.'

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com