DeVILBISS, 3M, Pacer, POR-15, Altex Coatings

How much paint does it take to fully paint a car?

It depends on the size of the vehicle, and the type of paint used. There are formulas for sq. ft. coverage, but in my experience are not always reliable. Let's take a Holden Commodore for example, which would be a fairly common size. In a base coat /clear coat (BC/CC) application, I would mix 2 litres of base coat, (perhaps one litre with an HVLP) which thinned to spraying consistency would give me 4 litres of sprayable material, and should provide adequate coverage. However, some are more transparent than others, and additional or less material may be required. Paint booth lighting is essential to ensure proper coverage.

After applying the base coat, I would mix two litres of clear, which reduced would give me three litres of sprayable material (two coats at approx 1 1/2 litres per coat). An additional third coat could be applied if desired, but be sure to watch for excessive film build which can lead to dulling or solvent popping problems. If you don't have access to a paint mixing system, then buy more than you need. There is no way to fix a paint job that does not have adequate coverage except for repainting the entire car.

What are some Important things to remember when using Aerosol cans?

Shake can well
If Laquer apply 3-4 Layered Coats
Any metallics apply 2 coats of clearcoat
Metallic colours can change according to the distance the can is held from the area to be painted, e.g. a close distance will be a darker shade, while a further distance will make a lighter shade.

How do you properly adjust a standard spray gun?

For a conventional suction feed spray gun. Set your air pressure first. The gauge at the gun should read approximately 380 kPa(55psi) with the trigger pulled far enough to allow air and not fluid. Point the gun at a piece of masking paper, and pull the trigger a bit further to allow fluid. The pattern should be convex, with slightly more paint in the centre than the edges. When you spray with a half overlap, it evenly distributes the material.

Can these same tips be applied to airbrushing? I am trying to airbrush designs on my motorcycle. Please let me know.

I generally use acrylic enamel (uncatalysed and reduced to a very thin viscosity) for air brush work, although I admit I don't do much of it anymore. It might be a good idea to get your base colour finished with a urethane clear coat so you have a nice base to work with. After you are happy with your design, clear over the acrylic enamel with the same urethane clear. It sort of goes against the rules, since uncatalysed acrylic enamel SHOULD wrinkle when clear is applied over it, but maybe because it is so thin it doesn't (or at least it hasn't for me). Lacquers dry too quickly and plug up on the tip of the air brush, and catalyzed paint cannot be stored. Acrylic enamels are cheap, and you'll only need a few basic (bright) colours to tint with blue red yellow black and white to give you all the colours. Oh yes, one last thing, don't buy tinting colours, buy mixed colours. The tinting colours don't have driers added and may not work properly.

What type of paints are used on automobiles?

Japanese Varnish: In the early years, between 1900 and the 1920's, Japanese varnishes were used. The varnish was applied by brush. Nitrocellulose Lacquer: in the 1920's, several paint manufacturers were involved in the development of nitrocellulose lacquers. This paint had rapid drying and low viscosity properties, and was applied with air pressure through a spray gun leaving a hard dry finish in approximately one hour. When rubbed, polished, and waxed, it far surpassed in durability and appearance the qualities of the Japanese lacquers. Synthetic Enamel: In the mid 1930's, a new and completely different type of paint was developed, the alkyd or synthetic enamels. It proved to have superior qualities in film strength, adhesion, lustre, flexibility and durability over all previous paints. The resin base was developed from the reaction between phthalic anhydride and glycerin, with gums, oils and plasticizers added during the manufacturing process a drying oil such as linseed, a polyhydric alcohol, such as glycerine, and a dibasic acid, such as Phthalic Anhydride. It dries by solvent evaporation, like the lacquer paints, but the resin remains soft and sticky when no solvents are present. It cures to a hard finish by absorption of oxygen from the air. The curing process can be accelerated by heat, and several methods of baking enamel were developed. Unlike lacquer, when dry, it needs no polishing to produce a high lustre finish. Acrylic Lacquer: As time passed, chemists developed a substitute for nitrocellulose lacquer, using an acrylic resin as a base. The resins used in acrylic lacquer tend to be slightly brittle. This deficiency is overcome by the use of a plasticizer (a liquid that is a solvent for these resins and softens them slightly). A cellulosic resin is any resin derived from cellulose (pure cotton). Acrylic lacquer was used extensively by General Motors. Acrylic Enamel: During the late 1960's and early 1970's, technology brought on the development of acrylic enamel, which was harder and more durable. Chemically, it is a cousin to synthetic enamel, but is modified with acrylic resin, and is not soft and sticky with no solvents present. It cures further with the absorption of oxygen from the air. Unlike the lacquers, which remain soluble in solvents, the enamel family is insoluble in solvent when cured. An acrylic resin is chemically any polymer whose basic monomers are chemical derivatives of acrylic acid. Polyurethane Enamel: In the mid 1970's, polyurethane enamel was developed to withstand the severe stress of high speed airplane surfaces, which are subject to rapid temperature changes and flexing. This paint was much more durable than the acrylic enamels. Acrylic Urethane Enamel: Acrylic urethane enamels were developed to withstand environmental elements, such as acid rain and ultra violet rays. It is the most durable paint to date.

How do you remove fisheyes or water spots that end up in the paint due to the compressor?

You can't. The affected areas will have to be sanded and repainted. A good water trap is very important when painting.

I have a question referring to fisheyes on paint. What exactly causes it? How can it be prevented?

Fish eyes are caused by contamination usually containing silicone, which messes up the surface tension of the paint. To prevent them you need a very clean surface and a clean air supply. As a last resort you can use some fish eye eliminator, but use caution since it might result in loss of adhesion.

My question(s) are: 1. What causes fisheye. 2. What do I do to prep the hood for repainting. 3. Is there an additive that will stop this from occurring?

After sanding, ensure the surface is clean by washing with a final wash like Prepsol, and check your air supply. You need a good water trap and clean lines. Acrylic Enamel is prone to fisheye easily. If you must you can use a little fisheye eliminator, but only if you absolutely need to.

Will I really get a high gloss finish by putting say 6 very thin coats of lacquer on ??? It just seems to be building up to a 'satin' finish.

Lacquer is unique, as it does not undergo any molecular changes when it cures. It dries by solvent evaporation alone. The reason for applying several thin coats is that the solvents may become trapped, and the paint may appear dry on the surface, but will be wet underneath. Also, piling on heavy coats may result in checking problems. Nitrocellulose lacquer, or acrylic lacquer will dry to a dull shine (satin). It has to be polished to get a good gloss. Fortunately, although lacquer has many drawbacks, it is very easy to work with. Apply it, wait till it dries thoroughly, and polish it.

Is it possible that slapping, or even hitting a car can cause the paint to chip? What does cause paint chips??

Paint chips from a loss of adhesion to the substrate. This can occur as a result of several factors. First, poor prep work before painting, inferior product, or sometimes from a sharp impact from a hard object, which might abrade the paint. (Hail does not chip paint, but gravel will). Perhaps if you were wearing a ring it may cause the paint to chip. It is very unlikely that the impact from a hand would cause properly applied paint to chip.

What are reducers or thinners and why do we need them?

Aliphatic hydrocarbons (Mineral Spirits- V M P, Naphtha) Aromatic hydrocarbons (Toluene, Xylene) Esters (Ethyl Acetate, Butyl Acetate) Ketone (Acetone, Methyl Ethyl Ketone (MEK)) Various combinations are used along with other additives (retarders, accelerators, and levellers) to reduce the viscosity of the material to a sprayable consistency and accommodate climatic conditions. In general, the smaller the molecular size of the resin (high volume solids), the less reducer will be required. Some products require very little or no reduction. I recommend following the manufacturers directions unless you have extensive experience in spray painting automotive finishes. However, in a pinch, the general rule is that reducers are downward compatible (i.e. you may substitute acrylic enamel reducer for enamel reducer, but NEVER vice versa. The solvents are weaker and you'll end up with an ugly curdled mess in the bottom of the paint gun).

What causes rust?

Corrosion is caused when an area of metal has a positive charge and another has a negative charge. Water acts as an electrolyte, allowing current to flow between these areas. During this process the metal absorbs oxygen from the water and forms iron oxide (rust). Salt water conducts electricity better than fresh water so in areas that use salt on the roads or if you drive on beaches, this process is greatly accelerated. The objective of applying a protective coat of paint is to insulate the metal from water. To ensure that no rust is present before we coat the metal, we clean the metal with an acid (phosphoric based, which leaves a thin film of iron phosphate or zinc phosphate that prevents flash rusting), and then apply a zinc phosphate coating which neutralizes the acid, and promotes primer adhesion. Zinc (galvanized and zinc rich primers) competes with the iron for oxygen, and becomes the sacrificial metal which corrodes, leaving the iron undamaged.

How long can you keep unmixed paint after you have opened it?

It depends on the type of paint. Some paints (urethanes or epoxies for example) do not depend on air to cure, so they will store well, in some cases indefinitely. Other types such as enamels utilize the properties of air to cure (solvent evaporation and oxygen to induce cross linking) and have a relatively short shelf life.

What is the best and quickest way to strip the paint off of a car?

The most common methods of paint removal are sandblasting, plastic blasting, chemical stripper or sanding. Sandblasting is not recommended as the high energy tends to create heat and warp the sheet metal, which creates a whole new set of problems. Plastic blasting is good, but expensive. Chemical stripper is fairly inexpensive and fast, but it is quite messy and be sure to mask or remove all the trim and plastic lens coverings. Additionally, caution must be used to avoid skin or eye contact which could result in severe injuries. A dual action sander (set to strip mode) with 80 grit paper will do the job nicely, although it may take a while. Follow with 180 in oscillating mode to remove the circular patterns in the sheet metal.

What is the basic technique of spraying?

You're in the paint booth, and you've used compressed air to blow dust from the panels, edges, beneath the mouldings and lights, and from the masking paper and the wheel covers (You do this outside the booth first, then again in the booth with the exhaust fan running, starting furthest away from the fan). You then have washed the vehicle with a Final Wash or Prep Wash (other washes contain silicone which cause fish eyes). You finally wipe the vehicle with a clean tack cloth and you're ready to spray. Occasionally, even after reducing the paint to the manufacturer's specifications it may be too dense to spray properly. The usual spec is about 15 seconds in a #4 Ford viscosity cup. Translated into English, that means about 4 seconds to stop dripping off the end of the stir stick. Turn your regulator to about 50 lbs, and get a nice oval pattern. Trigger the gun so that air passes through the cap, but no fluid comes through. Holding the tip of the gun about 20-25cm perpendicular to the surface, start your pass along the panel at a hand speed of about 30cm per second and squeeze the trigger to allow fluid. At the edge of the panel, release the trigger to stop fluid but still allow air. This constant air flow ensures that the air is not pulsing with bursts of pressure. This could cause excessive build up at the ends of you pass, leaving runs and sags. Don't stop at the edge of panels either, as this will also cause build up of material. On the back stroke, overlap half the first pass (the edge of the paint should appear dry, and the centre wet. This is known as a medium wet coat), triggering the gun as before. Always begin painting furthest away from the exhaust fan, so that you are painting over the overspray. Otherwise, overspray will settle onto the painted areas and may not blend in, leaving the surface dry and dull in appearance. With base coats, wait until the coat of paint is DRY before applying the next coat. Otherwise wait until it is almost dry, but a little sticky (the directions are usually close). If you get runs, drips, sags, don't try and fix them while you are painting. You will likely create more problems. They are easy enough to repair after the paint has cured.

What do you need in the way of ventilation?

Nearly all the materials used in automotive refinishing are hazardous to your health, the paint especially so. The catalysts usually contain Diisocyanate Prepolymer, and that is the main concern. It attacks the central nervous system, and can cause permanent injury. A good air flow and a fresh air mask should be used. If you don't have any bronchial problems, then an activated charcoal mask can be used. I have used the charcoal mask for years, but now my lungs seem to have an asthmatic reaction to the fumes and I strictly use the fresh air system. Also, some paints contain lead, which may have negative effects on your health when painting or sanding.