How To – Understanding Automotive Paint Choices

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    There are a variety of different types of paints used on vehicles today and the choices are as wide as their price range. Lets take a look at some of the paint choices you have when you want to perform an overall or repair paint job.

    First we should understand that some paints are called single stage. This group is usually limited to enamels and urethanes where a single can of paint includes both the base color and the clear shiny finish. You usually apply one half coat and 2 full coats of a single stage paint and do not need to clear over it for your final finish. Specialty Paints like powder coating and epoxy paints may or may not need a clear coat.

    Two Stage or base and top coat finishes require that you apply a base color coat that looks flat and then paint over it with a clear top coat for protection.

    There are many other techniques including candy paints which require many coats of paint but the difference we are covering is the difference between a single stage that you can apply and walk away from and a 2 stage that must have a clear top coat.

    When you are asking for paint most beginners should use a single stage paint because the results are more forgiving and the paint is always even if you apply it correctly.

    Now lets talk about paint types

    There are 3 basic types of car finishes Lacquer, Enamel and Urethane

    Lacquer paints are really an historic paint choice and are not used on new vehicles. If you are restoring an older car you may choose this paint type to match its original finish or you may use it to get a specific technique but Urethane paints can provide the same look with harder surface protection.

    Lacquer is still used today for primer surfacers and other under finish products. They allow fast dry times and because of the heavy materials in Primer surfacers which are made for sanding the lacquer thinner is a good choice.

    Lacquer paints also require a larger amount of hand work. You can expect to sand color coats between the many top coats that are needed for a full paint job. Most Lacquer finishes will require more then 5 top coats.

    Special techniques such as Candy Apple where a silver undercoat and a translucent red, blue or green top coat are available in Lacquer and the control of the color is based on the under coat showing through evenly. Urethane Enamels can also produce a similar result in a single or dual stage paint only requiring 1 or 2 full coats of a single color.

    Synthetic And Acrylic Enamel Paints are a medium range paint that is stronger then Lacquer Based Paint. 

    Synthetic Enamel should be thought of as a Utility Grade Paint. Although you can probably get the same metallic finish mixed in Synthetic Enamel based paints they are not as strong as a urethane and will last only a short time. For this reason they are great for vehicles that will see short lives in the field and many box and tractor trailers which have their side logos changed can be painted in a lower cost enamel. Synthetic Enamel is usually only available in premixed colors without the option for tinting.

    Acrylic Enamel paints are used with a Urethane Hardener which will increase their durability. Acrylic Enamel Paints can be produced in a standard Batch of premixed colors or they can be mixed to match your car. Technically the introduction of a hardener brings the standard Enamel paint into the Urethane category but they are not quite the same.

    If you are painting a Tractor or an old beater a gallon of Acrylic Enamel with a Hardener can be purchased for maybe $125 and should produce a quality finish that may last about 5 to 7 years.

    Urethane Finishes are probably the best commercially available paint choice the variety of colors are unlimited unlike Synthetic Enamel that comes in a standard set of premixed colors, Shop Grade Urethane paints can be mixed to match any car color or tinted to match variations in colors that happen due to the finish ageing from exposure to sun and the elements. This is why Urethane paints are the best product for repairs and full paint jobs. Unlike Acrylic Enamels that have a Urethane Hardener paint that is produced as a Urethane Paint must always use a hardener.

    Other Paint types you will run in to

    Epoxy Paints are not usually used on automotive vehicles but are great for boats, airplanes and other vehicles that require an extremely durable surface. If you paint with epoxy paint you need to wear an in-line forced air respirator or you will die…. well maybe not die but epoxy paint is very toxic so only use it in a professional booth with a forced air respirator and a full tyvek paint suit. This paint is also good for Frames and suspension parts but because it is so expensive don’t use it unless you need to.

    Powder Coating is a special process that requires bakeing and is not used normaly on exterior finishes but may be used on your engine especially the valve covers. This process produces toxic fumes during baking  although there are nontoxic versions coming to market. NEVER use your home oven for baking parts if you ever intend to cook food in it again.

    Paint Mixing
    Most paints today come ready to shoot once you add a hardener. Unlike just a few years ago where you had to measure out the paint then add reducer to thin it to the proper viscosity the hardener is to be used in 3:1 or 4:1 Paint to Hardener ratios.

    Cleanup and Pot Life
    Pot life is the time that mixed paint can sit in your spray gun or in your mixing container.  Lacquer Paints and Synthetic Enamels without a hardener can be stored for a few weeks to 2 years even after they are reduced but once a hardener is used in the paint you have from about 30 minutes to 2 hours to use it before it turns into a gel and starts to harden.  If it is hot out over 80F or if you add dryers you can see that time reduced even more. For this reason it is best to clean your gun between coats, throw away any mixed paint and use a new mixing container for the next batch.

    Note: when performing an overall paint job you will want to do your door jams, under hood, inside trunk and other areas first then allow a flash time of 30 minutes to 8 hours before you paint the outside of the car. Don’t try to keep that paint or mix it back in the unused original can or it will turn all of your paint to garbage. Once your paint leaves the original can it never goes back in.

    Dry Times
    Drying times for paint are effected by the products used in the paint and the drying method. Commercial shops can bake the paint at 140F for about an hour and the car can be ready to continue work or to deliver to the customer after a short set time. Lacquer based paints will dry the fastest however Urethane paint that is specifically made for quick turn around can be use even in air dry settings.

    Flash Times vs Drying Times when you are painting a car you need to use a number of coats of paint to build up the finish. Flash time which is usually about 15 to 30 minutes between coats allows enough of the thinners to escape so you can put another coat on. Drying time refers to the ability to work with the surface. Most top coats can be applied over a base coat in a number of hours but for best results you may want to wait overnight or up to 8 hrs. The same is true when painting more then one color (in a two-tone or stripe) or when you need to tape off fresh paint. You should check your manufacturers recommendations but a full 8 to 12 hours is needed before you can tape on a fresh coat of paint with professional painters tape. For Buffing and sanding you may need to wait from 18 to 48 hours. Now times are different for spot paint jobs fixing a small repair where you use a heat lamp or when you bake the whole car at 140F for an hour.

    As a rule of thumb for home paint jobs

    15 – 30 minutes flash between layers – gives you time to mix more paint and clean your gun.
    Overnight between doing door jams or before you apply tape.
    One Week before you compound or sand out the clear.
    One Month before you wax and never use wax that contains silicon.

    for the most part Lacquer paint is the least toxic followed by straight enamel then urethane then epoxy each require the use of a respirator however urethane and epoxy paints contain poisons and should only be used in professional booths with inline forced air respirators. Always read warnings and directions and then actually follow those directions… don’t just read them and then say Yea Sure I Read it.. Or you could DIE.

    Paint Additives  additives allow you to add features to your paint to adapt their qualities for your application.

    Flex Agents are used when you are painting a part like a bumper cover or ground effects that will flex and move with the car. If you were to use a hardened paint you will probably endup with chips and cracking. You should also use a flex agent when you paint a plastic car like the Saturn.

    Hardeners were already mentioned they are a catalyst that is added to urethane or enamel paint that improves durability.

    Fish Eye Eliminator is an additive that is used when you are painting a car that might have oils from wax or your hands. It is good when performing touch-ups or in an emergency during a full paint job.

    Chip Guard is a product not always used but can be used around wheel wells to reduce the likelihood of debri causing paint chips. It takes on a textured appearance and is not very attractive.

    Flattening Agent will turn any paint into a flat color. This is good for custom stripes it can also provide a low gloss for engine compartments.

    Drying Agents are another emergency fixer. They are added to paint in high humidity settings to allow the solvents to escape the paint before they end up with a fog or milky quality due to the paint skinning over and solvents being trapped.

    There are many other things that need to be covered about paints and additives and their proper use but you should also seek the advice of your local professional paint supplier. Just remember to stay away from cheap synthetic enamel paints if you want your car to look nice for more then a year. And once you mix in a hardener clean your gun within 30 minutes and toss the paint away.

    See our other HowTos on Primers, Clear Coats and Specialty Finishes.

    The YouRepair Store carries a full line of Automotive Custom Paints , Paint Guns, Compressors , Tools and other items you will need for your project.

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