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HOME RESTORATION
AUTOMOTIVE PAINTING
Part 1.
Paintwork is a restoration task that is often, like the engine build, left to professionals. Professional car painters have more and better equipment at their disposal, along with a large amount of experience and training. However, unless you pay top prices, you cannot guarantee that they are going to take more care of your car than they do of the usual insurance repairs and to-a-price resprays that make up most of their work.
It is possible for the home restorer to achieve results as good as a professional, though it may take ten times as many hours and a lot of mistakes. However, if you paint a car yourself, you know for sure that those rusty patches have been adequately repaired, and no rust, water or dirt is trapped in any crevices waiting to rot out your panels within a couple of years.
Choosing a Paint Shop:
Care is needed when choosing a paint shop for your car, to ensure that they work to high standards, as problems with poor preparation and shoddy technique may not become visible for up to two years after the paint was applied.
When obtaining quotes, be specific about the work you want done. For example, you may wish to have the entire body shell stripped, all dents and surface imperfections removed, the car painted with two-pack paint, and the box sections treated with rust proofing chemicals. If you ask only for a quote to paint the car, painters will tend to quote for a respray of the outside of the shell with minimal surface preparation. Get an itemised quote if possible. You get what you pay for.
Inspect the premises where the painting is to take place. The paint shop should be clean, well-lit and contain a spray booth. Tools should be neatly stored, clean, and in good condition. Staff should be wearing appropriate protective clothing, and should not be painting outdoors or in the same room as general preparation work is done, or sand and dirt will accumulate in the wet paint.
The process of writing a quote should take more than just a few minutes and should involve a thorough assessment of the car. For this reason, paint shop owners may be wary of writing quotes for potential time-wasters.
Restoration shops are less likely to have spray booths, and the best restoration shops will have their own fully equipped paint shop, or farm painting out to someone better equipped.
Restoration shops that paint cars in their workrooms or even "out the back" may still give excellent results, but they have to work much harder under those conditions to get them.
Finally, contact local car clubs and get in touch with the owners of concours competition-winning cars. Ask them where they had their cars painted. This should provide you with a few leads.
Paint Types:
Automotive paint is made up of many compounds, often toxic. The ones of interest to the restorer are the pigment (colour), and its delivery medium (the stuff it is dissolved in that allows it to be sprayed from a gun). All types of paint follow a basic principle - primer is sprayed onto the surface to prepare it for the top (colour) coats. The primer provides an even, neutral base for the colour coats; colour paint does not have good natural adhesion to wood or metal.
Paint is available in many different types - choosing the type of paint to use is very important. application techniques, cost and the resulting appearance vary widely between them.
Nitrocellulose Lacquer;
One of the oldest types of car paint still available. Nitrocellulose is based on cellulose, as the name implies, and is an "organic" paint finish. It was used on production cars up until the 1950's to 1960's depending on the car manufacturer.
It is not particularly resistant to light or pollution and consequently more modern paints have been developed that last longer. It also takes a long time to dry. Environmental regulations make the purchase and legal use of nitrocellulose increasingly difficult in many countries, due to the amount of organic solvents that evaporate into the air during painting and drying.
Acrylic Lacquer;
Used on many cars from the 1950s to the 1970s, and some, such as Rolls Royce, until the late 1980s. The paint is mixed with paint thinner which evaporates, leaving the paint pigment on the car. The finish is usually deep or glass-like, suiting classic cars. However the finish must be buffed regularly to maintain it's look, and is not as long-lasting as 2 Pack. Acrylic lacquer is the paint of choice for the amateur painter, especially for cars of the period. It has a relatively fast drying time, preventing dirt from sticking to the finish.. The fast dying time permits dust or painting mistakes to be sanded down within a relatively short time of paint application.
Acrylic Enamel;
A cheap type of paint often used on commercial vehicles. The only advantage is low cost, but you get what you pay for; the finish is somewhat dull. This paint should only be considered for showroom finishes for cars originally painted with it.
2 Pack;
Paint used on all modern cars, used increasingly since the 1970s. Very easy and efficient to paint with, requiring less coats than lacquer and drying to a "showroom shine" with no sanding or buffing, in the hands of a skilled painter. The finish looks like plastic, although a skilled painter can reduce this effect. It usually does not look "right" on classic cars.
The finish is also longer-lasting and more damage-resistant. The name comes from the mixture of paint and hardener that dries by chemical reaction, conceptually similar to epoxy glue. This paint contains is ocyanates. If that word looks familiar, think of cyanide. When this paint is being sprayed, the spray can be considered as dangerous as sprayed cyanide gas. In the worst case, death can result from inhalation of 2 Pack paint fumes. In the best case, the immune system is seriously impaired resulting in increased susceptibility to minor diseases and a great magnification of the symptoms.
This paint is not suitable for use by the home painter. Professionals must wear full-body protection with air-fed masks kept at higher than atmospheric pressure to prevent is ocyanates from entering the mask. Spraying is done in a filtered spray booth equipped with heating equipment to bake the finish and reduce the drying time.
Most of the paint types above are not compatible, and often different brands of the same type will react. Enamel over lacquer usually does not work, resulting in an unpleasant chemical reaction. Lacquer over 2 Pack usually works, but if there are scratches in the 2 Pack the lacquer will eat into the 2-pack from beneath, via the scratches. Fortunately, the results are immediately obvious. The only solution when this occurs is to strip the surface back to bare metal. When painting over old paint, always find out the correct type - the paint supplier will be able to help.
Metallic and Pearlescent Paint;
Most modern cars are available with pearlescent or metallic paint, although metallic paint has been used on cars including Wolsleys since the 1960s, and pearlescent is a development of the American custom hot rod scene of the 1970s. Both these paint types rely on flakes of material added to coloured paint, which is then coated with several layers of clear paint which are buffed to give the final finish. If the flakes were exposed to the elements or buffed, they would degrade or oxidise, ruining the finish. Therefore the "clear over base" method is used.
Metallic paint consists of tiny aluminium flakes, purchased separately from the paint and mixed into it to give the required metallic effect. The effect is controlled by the proportion of flakes used, their size distribution and their reflectiveness, and dozens of types are available.
With practice, and preferably some training, a DIY painter can master metallic and pearlescent painting to give acceptable results. Fortunately, however, most classic cars are painted in solid colours.
Next month ……”DIY Car Painting”.
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