Fiberglass (Fiber Reinforced Plastic) is often susceptible to water incursion and/or sun damage depending on the resin used. Epoxy weakens, with time, in sunlight. Polyesters are subject to water infiltration and vinylesters are not as strong as epoxy; though are stronger than polyesters.

Water incursion will cause blistering or bubbling, though this typically takes years to develop.However, once blistering appears its only a matter of time before the composite (fiberglass and resin) delaminates and you have major problems on your hands. This is especially important in boating.

Sunlight, usually with epoxy resins, will cause the composite to crumble. As you might imagine this is pretty bad.

To add an additional barrier to both water and ultraviolet light (sunlight) paints are used (in the business they are called industrial coatings) as a protective layer against these incursions. They look good too.

In this hub I will recommend two types of paint (not brands) and cover the pros and cons of using them.

With this information I'll also recommend two painting techniques. Any paint type covered here can be applied with either technique.

This hub covers the basics of these methods. For full instructions on either look to the bottom of this hub for links titled Roll and Tip Method of Painting and Spray Method of Painting.

There are two major categories of paint. They are both polymers (plastics based). One uses exposure to air to cure; the other a catalyst, heat, and air.

Because these paint types are basically plastics in a volatile liquid they adhere well to epoxy resin, vinylester resin, and polyester resin* as long as those resins are dry to the touch.

Basically any resin based paint is suitable for application on Fiber Reinforced Plastic (FRP), but I recommend using epoxy based paints with epoxy based FRP resins and polyester based paints on polyester based FRP. The reason is better bonding to the FRP.

However, should you be painting a boat or other FRP object subject to temperature extremes and/or water immersion I recommend epoxy based paints regardless of the resin used in the FRP. Epoxy, as long as it is protected from sunlight, is both strong and flexible. Naturally, the pigments in an epoxy based paint will provide the ultraviolet barrier epoxy FRP needs.

* ^{Listed in order of overall strength}

Paint typically consists of a vehicle (liquid), binder, and pigment. In paints used for durable plastic coatings these are volatile organic compounds (liquid carrier), polymers (binder), and pigment (color). I do not recommend powder-coat due to the high temperatures required to bond the coating. Since powder-coats require temperatures of 300~350F fiber reinforced plastics will melt.

A component of most of these paints is Volatile Organic Compounds (VOCs).

VOCs are liquids designed to evaporate at a set rate....usually quickly. The idea is for the liquid to remain long enough for the paint to self-level, but evaporate quickly enough to present a durable coating. VOCs serve as a vehicle for the paint pigment & binder and keep those pigment particles in suspension until the paint is applied, self-levels, and dries. VOCs also insure faster drying times.

Both one part polyurethane and two-part epoxy paints use VOCs. Without VOCs drying times would be measured in days or weeks not hours. In some situations (professional shops) external heat sometimes brings those times down to minutes.

As you might imagine anything that evaporates this rapidly is not good to breathe so proper protective gear should be considered when applying these paints. A simple "hospital" style mask is not appropriate as it allows VOCs to enter your lungs. A better mask is one designed specifically for painting.

Another component in polymer paints is the binder.

Binders are the chemical compounds that cause the pigment particles to bind to each other. The binder is typically a plastic including resins such as acrylics, polyurethanes, polyesters, melamine resins, epoxy, or oil.

All of the coatings above work well with metal or wood. Only the bold faced types (above) work well on fiberglass.

FRP is different because of it's typical uses of Fiberglass (FRP) and the additional protection specific types of FRP require. Oil, melamine, and acrylics have too many disadvantages to be effecively used on FRP.

Paints for FRP should not be oil based and melamine is not durable enough, to make a good coating. Acrylics, polyurethanes, polyesters, and epoxy are best. Note that the pigment in epoxy paint protects it from ultraviolet light. In matter of fact the worst thing for epoxy is direct exposure to sunlight without some sort of protective coating.

When applying any of these paints there is very little difference in the two methods used in applying them. Naturally, you want to read the manufacturers label carefully for any special circumstances. Ambient temperature is the most common reason for differences in application technique. Higher temperatures typically requires that a thinner or "brushing liquid" be added to keep the paint from setting too soon. As you might imagine a paint that sets as you are using it is bad news.

Paint technology has gotten so good that some car manufacturer paints make one big molecule covering the car from front to back. Naturally, this makes a very durable coating. Automotive paints are typically polymer based.

Pigments comprise the smallest percentage of a paint. Though certainly most modern pigments are chemically derived, manufacturers tend to keep the actual sources and formulations a trade secret.

As with fiber-glassing, preparation is almost everything. Relative humidity should be below sixty (60%) percent and temperature should be between sixty five (65°) and ninety (90°) degrees Fahrenhiedt or 19° to 35° Celcius. Note that the lower the temperature (within the range) the longer the drying time.

If the humidity is too high you'll trap water droplets in your paint and end up with a dull looking finish. This cannot be buffed out and can only be "cured" if the offending layer is sanded out and repainted. Worse, water droplets can migrate into your fiberglass can cause it to de-laminate.

In painting if there is too low an ambient temperature the paint won't harden. Too high a temperature and the paint will set almost instantly.

Paint has to have time to "self-level." This means that any bumps, brush marks, or droplets left by the spray gun or brush have to have time to level out and become smooth.

Surface prep is very important. Paint will not stick to oily or greasy surfaces. The oil from your hands is enough to prevent adhesion. So a clean surface is vital. Also, if the surface is too rough or has gouges in it those blemishes will show right through the paint.

Paint will not adhere well to glossy surfaces so sanding is also a vital step. This is especially true of you are painting over a previous coating of poly or epoxy. The best bet it to use a very fine "wet" sandpaper to be sure you have just enough roughness for the paint to stick.

Contrary to popular rumor you can paint a single part paint over a two part paint. It is not advisable to attempt to paint with a "two parter" over a single part paint though I've had good luck with this too. The key, of course, is preparation.

Rules of Thumb: If you are painting over;

• a fresh fiberglass or metal surface use a primer first
• a pre-primed surface, rough sanding (120 grit) first
  
• a first coat painted surface fine sandpaper (400 grit) first
  
• Succeeding layers wet sanding (1000 and higher grit)

  
  

The steps for painting with primer are not as rigid as the finish coats. By and large you can apply primer a bit thicker and you certainly don't need a "tip" method to smooth it out. Primer provides an excellent bond between fiberglass and the finish paint. It also provides an additional moisture barrier.

Be sure that each surface to be painted is clean and completely dry.

The typical steps to preparing the surface just prior to painting is to sand, blow or brush the surface free of particles, denatured alcohol rub, water wipe-down, and a tack rag.

There are two main methods of applying paint to various surfaces. These methods are geared toward the home hobbyist or adventurous hobbyist depending on available equipment and/or experience.

Note: You do not have to be a professional to spray paint, but if you've never done it before I strongly advise practicing on something you don't mind throwing out. Even a scrap of cardboard will do.

Spray: The paint is applied with a compressed air/or pumped pressure spray gun. This requires a compressor and/or a good quality spray gun, paint filters, paint stirrers, eye and hand protection, masks (you don't want to breath the stuff), solvents, containers, and plenty of clean rags.

I recommend compressed air and an High Volume Low Pressure (HVLP) gun. The advantages are only low pressure (about twenty-five to fifty pounds) is needed. Since an HVLP gun applies more paint that air, as the name implies, you'll also have fewer airborne particles to breathe. You'll also get most of the paint on your target; not everything else.Note: paint settling on objects not intended for paint is called "overspray." HVLP helps you prevent overspray.

Advantages;

• Spraying is quick and provides good, consistent, coverage with practice.
  
• Spraying can be done by one person
• Gives professional looking results
• Has reduced drying times

Disadvantages;

• Takes some practice to get it right
• Goes on thinly and so will take more applications for a good coverage.
  
• Lots of cleanup is required
• Risk of overspray (getting the paint on surroundings)
• Inhalation risk. This stuff can damage your lungs.

Roll and Tip: The paint is applied with a roller and then followed up almost immediately with the tip of a fine bristle or foam brush. Tools requirements are a solvent resistant roller, solvent resistant roller covers, brushes, containers, paint filters, eye and hand protection, stirrers, solvents, and plenty of rags.

Advantages;

• Professional looking results (with practice virtually indistinguishable from spraying)
  
• Only a moderate level of skill required
• Less risk of breathing VOC fumes
• Fewer coats required (it goes on thicker than spray)
• Easier cleanup

Disadvantages;

• Takes longer
• Requires two people or one (very) fast painter
• Requires a sectional^* approach
• Longer drying times.

  
  

* ^{In this instance a "sectional approach" means rolling then brushing 3 foot square sections. This approach will prevent an area painted at the beginning from drying before the brush "tipping" is applied.}

Refer to the photographs at right.

Tools required for spraying include;

• Air compressor and paint gun
• or piston sprayer
• Filters
• Paint (many brands can be sprayed or rolled)
• Thinner (depending on ambient temperature)
• Drying agent (depending on ambient temperature & humidity)
• Solvents (for "oops" and cleanup)

Notice in the video above that the painter begins spraying air just prior to shooting the paint. Much like a digital camera, the trigger on the sprayer has a "half" and "full" setting. This is a really good idea because it establishes a consistent flow of air prior to any paint coming out. This prevents spatter.

He starts from the middle and works out. Professionals may deviate from this, but if you are new to this you may be surprised how quickly you'll tire of being bent over. By starting in the middle and working out your back will sustain less stress. Do the middle when you are fresh and the edges (where less bending over is required) toward the end. This is the proper pattern to use in painting with a sprayer too.

Notice too that he keeps the gun at a consistent distance from the hood. This is also important. The farther the gun is from the hood the thinner the application of paint; the closer the thicker it goes on and the higher the risk of runs or droops.

He also paints past the object being painted. This is perfectly acceptable and insures that you don't stop the flow of paint right at the edge of the object being painted. By painting past the edges no thin spots are created at the edges.

He does not over do either. There is likely no more than a cup of paint on this hood, probably less. At this point he'll stop, allow the paint to dry, lightly wet-sand, clean, and then apply the next coat. This is very important to prevent drips, droopy spots, and runs. It is also important to apply multiple coats for a thicker protective coating.

Finally, the "rig" he is using is a High Volume Low Pressure (HVLP) gun. This type of paint gun is very efficient. It uses about thirty five (35) PSI which means that most of what's coming out of the gun is paint not air. Since there's so little pressure paint does not "splash" off of the surface, become airborne, and end up on items you didn't want to paint...or in your lungs.

Note that the painter is wearing a mask (not the right type either). Apparently the videographer isn't and is suffering for it.

Note: The mask he's wearing is not appropriate!

Tools required for roll-n-tip include;

• Roller (does not have to be high quality but should be solvent resistant)
• Brush (high quality china bristle or foam [I prefer foam it's much cheaper])
• Stirrers and Filters
• Paint (many brands can be sprayed or rolled; check with the manufacturer)
• Thinner (depending on temperature)
• Solvents for cleaning.

  
  

First notice how clean the painter is. This is no accident.

You see that he has both the roller and brush near at hand. The point is he wants to use the "tipping" method as soon as possible after rolling on the paint.

The roller is used to get good coverage; the brush is used to smooth the paint for a glossy finish. Since all paint is self leveling using a brush in this manner insures that the paint seeks it's own level (and stays there) much sooner. This also insures a glossy finish almost as perfect as the spray on method. In fact this is such a good method, one would need a magnifying glass to see the difference.

Notice too that this is not a very big roller, that the area he's painting is fairly small, and that he applies the brush strokes very shortly after applying the paint. He also uses very little pressure with the brush.

The only error I see being made here is that he really should have the brush at about a 45 degree angle to the surface.

The photo at right contains pictures of logos and brand-names of various well-known, use tested paints. These are all polymer based paints. Some are two part "epoxies" others "polyurethanes." All provide excellent results and good protection along with a beautiful shine.

Consult the manufacturers or friends for information on the best paints to use.

Generally a one part polyurethane is good for external use, holds up well to weather and bright sunlight, but is not good for total immersion (underwater) use. Brands such as Petit, Interlux (BrightSide),and Altex make good one part paints.

Epoxy paints, on the other-hand, hold up pretty well to immersion service along with being durable outdoor paints. All epoxy paints are two part paints. Brands of epoxy paints include AwlGrip, Interlux (Perfection), and DuPont Imron.