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

August 21st, 2007 - Issue 17

In this issue:

• How you can determine the type of paint on your car.
• Questions & Answers: Questions from three of our subscribers are answered for you this week.
  

Before high-tech polyurethane paint products were introduced, cars were painted using either enamel or lacquer.

Each offered its own unique characteristics. Enamels being quick and easy to work with, generally covered in one or two coats and didn't require any clear coat or rubbing out.

Lacquer however, required multiple coats, but allowed imperfections to be easily rubbed out and quickly repainted. The fast drying time enabled painters to fix surface blemishes almost immediately.

Although both enamel and lacquer paint products offer specific benefits, they cannot be used together on car bodies due to their incompatibility.

With surfaces properly prepared, it wouldn't be a problem to spray enamel over lacquer; however lacquer applied over enamel will almost always result in wrinkling or other severe surface blemishes.

This is due to the solvent base in lacquer paint (lacquer thinner) being too potent for the soft materials used in enamel paint products.

Product compatibility is just as important today. This isn't just confined to just enamel, lacquer or urethane bases either.

EVERY PRODUCT IN AN ENTIRE PAINT SYSTEM MUST BE COMPATIBLE WITH THE SURFACE MATERIAL TO WHICH IT WILL BE APPLIED, AS WELL AS WITH EVERY OTHER PRODUCT IN THE SYSTEM.

As you've probably guessed, this is very important to the success of any paint project.

For example, using a PPG reducer with a BASF hardener in a DuPont paint product is asking for real trouble.

The individual products were not designed as parts of a single compatible paint system and as a result, the color, adhesion and surface flow of that combination may well be adversely affected.

We will cover more on paint chemistry and product compatibility in future issues.

OK, so before you purchase paint for your car, you need to determine what type of material currently exists on the surface of the vehicle, whether it be enamel, lacquer or urethane.

In the case of newer vehicles, all factory paint jobs are going to be urethane based, as enamels and lacquers are being left behind.

There should be a specific paint code listed on the vehicles identification tag to enable you to find out what kind of paint was applied at the factory on your car.

In addition, you will also be able to determine the exact type of paint and color from the vehicle identification number (VIN) on older vehicles or from a separate paint and options tag on newer vehicles.

This all helps to easily identify materials when you are planning to match the existing paint.

If you're having difficulty finding the paint and options tag, staff at your auto paint and supply store should be able to offer assistance in determining where it is located on your vehicle.

If the car has been repainted since it left the factory, you will need to obtain the paint code numbers from the paint can used during repainting.

If this is not possible, contact the person who performed the paint job to attain the required information from them.

Before mixing the paint, it would be a good idea to confirm that the new paint is going to be the same color, just to verify that the new vehicle hasn't been repainted nor had the wrong tag attached.

If you cannot determine the specific paint codes or information relating to the type of paint used on your car, you yourself will have to test a hidden spot on the vehicle using lacquer thinner.

You could even possibly test an area already allocated for a repaint.

Take a clean white cloth, wet it with lacquer thinner and rub a spot of paint to test the reaction.

• If the color comes off immediately or the spot starts wrinkling, it shows that the type of paint is enamel.
  

• If however the color wipes off onto the white cloth only after vigorous rubbing, it is a sign of lacquer paint.

• If nothing wipes off onto the cloth, the paint is probably urethane based.
  

To find out if the finish on the vehicle includes coats of clear paint over its base color, simply sand a hidden spot using 600-grit or finer sandpaper.

A white sanding residue shows that there exists a clear coat finish. A color residue shows that only a color material was used to paint the body with.

Before applying fresh paint on the vehicle, it is vitally important to find out exactly what type of paint is currently on the surface.

About the only exception to this rule is where a totally new paint system has to be taken into consideration after bringing the vehicle body down to its base metal.

If you are at all unsure about the type of paint on your car after this test, or if you have any other related questions or problems, our advice would be to consult a professional auto body paint and supply store member of staff.

Remember, applying mismatched coatings to an existing finish can potentially ruin your whole paint job.


Questions & Answers

Our first question comes from Daniel Barnes.

Daniel asks:

I have primed my car with 2k-beige primer and at the moment it is sat there rubbed down to a 1500-grit sandpaper finish.

I rubbed it down in stages from 600-, 800- onto 1500-grit.

I have checked it over and over for any imperfections and all is well.

I bought midnight blue paint and was told to just mix it 50:50 with 2k thinner without any hardener.

The car is prepped including back of doors, door wells and the back of the boot and bonnet.

I was told that 5 liters of ready to apply paint would be enough, is this true or would you advise me to buy a bit more to be sure?

Also, I am unsure of the room temperature the 2k paint has to be applied to the car in, is it about 60 degrees Fahrenheit?

I just need to know a bit more about the base coat/room temperatures/how long you leave the paint to dry between coats?

Please could you give some more advice on the stages that come after the car has been primed?

Ans: 50:50 is the right mixing ratio for 2k base coat. As for the quantity of paint needed, this will usually always depend on the opacity of the color being applied.

For example, when covering a light colored primer, you will need to use more of a dark color (midnight blue) than a lighter color, due to the high contrast between the two.

Painting yellow or a similar light color over a light colored primer will generally require less paint.

The same rule applies when working with darker colors; if you use a dark colored primer such as dark gray, then less dark colored base coat will be required.

Discuss this with your auto paint supplier, they will advise you according to your budget, on the best paint setup for your project.

As for temperatures, the panel temperature should be around 25 degrees C with paint applied in a dry atmosphere.

The ambient temperature should also be around 25 degrees C, drying times between coats should be around 5 to 10 minutes.

Don't forget that 2k base coat is only a color and will require 2k clear coat lacquer over the top to give the newly applied top coat color a gloss showroom finish.

Usually 2-3 coats of lacquer is all that will be required.


Our second question comes from Albert Gommers.

Albert asks:

I'm painting a VN and have purchased a new front bar cover.

I have wet sanded it using 400-grit sandpaper and then cleaned it using wax and grease remover.

The problem is I can't get the paint to sick to it! I'm also having trouble with fry ups in the paint, is that because the temperature is too cold or because the surface is not clean enough before painting?

Ans: Firstly, establish what the the cover is made from. If it is a plastic type material, it will require an adhesion promoter.

This is a special type of plastic primer, which should be used once the cover has been flatted down and cleaned using wax & grease remover.

Usually this product can be purchased in aerosol form with 2 coats needed at room temperature, 25 degrees C.

Then a 2k primer should be applied over the cover, 2 coats will be enough.

If the cover is to air dry, leave it for at least 24 hrs at room temp.

Then wet flat using 800-grit wet and dry flatting paper.

Apply the color in light even coats leaving 5 to 10 minutes between coats.

Don't try to apply too much color with the 1st application, this is usually the cause of cracking or crazing.

Usually 2 to 3 coats of color will be enough, dry for around 30 minutes at 25 degrees C, then 2 to 3 coats of clear lacquer should be applied.

Again light even coats leaving 10 to 15 minutes in between. Leave to dry again for around 24 hrs at room temp.


Our third and final question comes from Mitchell Buckley.

Mitchell asks:

Here in the United States there is PPG paint and Dupont paint including several others. What brand do you recommend?

Ans: To be fair and honest, both brands are very good and there is very little difference between them both.

In terms of overall paint quality, there isn't much in the way of poor quality in use nowadays.

We hope these answers help guys.


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 discuss Nick & Scratch Repair and Panel Painting.

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com