Application Description

This article discusses GOLDEN products that can be used and gives our suggestions on how to apply them in the soundest manner. It is important to understand that these products have limitations when used for any exterior application. However, when the products are applied correctly, the resulting painted sculpture should last for quite some time.

It is equally important to realize the future owner's role in preserving this sculpture. As with an outdoor mural (or any artwork for that matter), there should be periodical inspections for early warning signs of failure, such as film degradation and discoloration. We suggest that the future owner be made aware of the products used in these sculptures and that they should keep this information in their records to assist any possible conservation or restoration processes.


Surface Preparation

Preprimed Fiberglass

Some fiberglass sculptures may arrive preprimed. These most likely have some sort of automotive primer intended for metal and fiberglass. If this surface is acceptable for the intended artwork, then skip down to the Painting Application section. 

Testing for Adequate Preparation

If you have any concerns about the preprimed surface, you should contact the people in charge of the committee and ask them what product has been applied. You can also test the paints you plan on using in an inconspicuous location on the fiberglass body. We suggest the "Crosshatch Adhesion Test" in which the paint films are scored with a razor knife. In a space of approximately 2 square inches, score a series of parallel lines about 1/8" apart. Then score another series (perpendicular) across the first ones, creating a crosshatch pattern of little squares. Finally, take a piece of ordinary masking tape, burnish it on the section, and lift off straight up from the surface. If there are no squares that lift off, then you have excellent adhesion between all layers. If a few squares come off but the majority remains, you may have sufficient enough adhesion, especially after the sculpture is clear coated. If most or all of the squares come off, this suggests poor adhesion. Note where the failure occurred. Did the primer come off of the fiberglass? Did the paint come off of the primer coat? This will indicate whether or not the primer is suitable or if it needs to be sanded to accept the acrylic paints.

If the priming was done poorly and is unacceptable, or the (bare or preprimed) surface is too rough or too slick, then sanding the surface may be required. Because of the unusual textures and other animal features, hand sanding is probably the most practical method.

CAUTION: inhaling fiberglass dust is extremely dangerous and should be avoided at all costs. Wear a properly fitting dust mask or have someone with appropriate equipment do your sanding. In general, any airborne dust or particulate is bad to inhale, but fiberglass is quite harmful to the lungs.

Sand the surface in a circular motion with sandpaper grits between 220 and 440. The surface should be wiped down with a damp rag frequently and inspected for glossy spots. Once there are no noticeable areas of gloss, give a final wipedown and then degrease (below).


Inspect the surface, looking for any greasy, oily substances. The fiberglass body was created in a mold process. Mold release agents (such as silicone sprays) may have been used to ensure the sculpture will pop out cleanly from the mold. It is imperative that these contaminants are removed by wiping the surface with either "degreaser" solvents made especially for this purpose, or isopropyl alcohol. This process will also remove fingerprint oils and other materials that may have accidentally been applied to the surface. Allow the degreaser to fully evaporate before priming.

Applying the Priming Coat(s)

It is critical to use a high quality product for priming any artwork. No matter how durable the subsequent layers of paints and varnish may be, they will only last as long as the priming coats. Keep in mind that artist materials are not intended for outdoor use, and that a gesso may be used with good results when all of these steps have been followed. However, failure to apply subsequent layers of acrylic paints, mediums and sealer coats may result in chalking of the surface or even worse problems. Most manufacturers of artist grade gessoes use Calcium Carbonate in their products
to provide tooth and a matte finish. Use of Calcium Carbonate in housepaints has been shown to cause chalking. While we do not anticipate this occurring with our gessoes on this project or on other applications such as murals (when the proper procedure is followed), we feel it is important to inform artists of this.

There are several options for priming the fiberglass body:

  • Automotive primers for fiberglass.
  • Professional grade, exterior housepaint primers specifically intended for nonporous surfaces.
  • GOLDEN Gesso blended 3:1 with GOLDEN GAC 200.

Apply either one or two coats of the primer and allow 24 hours to dry after the final coat is applied. The surface is now ready to be painted or decorated.


Product Selection

In general, most GOLDEN Acrylic products can be used for this application. GOLDEN Heavy Body, Fluid, Matte, Matte Fluid and High Load Acrylics, High Flow Acrylics, and Iridescent/Interference Colors should all have adequate adhesion. However, to increase adhesion and physical hardness of the acrylics, blend between 10 to 75% GAC 200. This is the hardest acrylic medium Golden produce; it extends paints while increasing durability.
Other brands of acrylics can be used; however, we cannot offer assistance for their use, as we do not know what their adhesion, permanence and durability may be. We suggest contacting the manufacturer of these products before embarking on the project.

Other kinds of paints, such as housepaints, oil paints, automotive, acrylic enamels, etc., may also be used for this application. Because of the infinite factors involved with using these products, we suggest contacting the manufacturer before use on the project.

Pigment Selection

Certain pigments are more fugitive than others, meaning that they are more prone to color fades and changes from exposure to sunlight and exterior environments. GOLDEN only uses Lightfast rated I & II pigments, with the exception of the Fluorescent products. Using anything less than Lightfastness I pigment may result in rapid color shifts when exposed to sunlight. Lightfastness information is available for GOLDEN products upon request. Even the use of GOLDEN Hard MSA Varnish (with UVLS) cannot insure fugitive materials (this includes papers, dyed fabric,
plastics, etc.) from some degree of fading. Some pigments react to the combination of sunlight, temperature, moisture and acidity present in outdoor areas.

Cadmiums and Ultramarine Blue are pigments to avoid outdoors, especially when used in glazes.

GOLDEN Suggested Color List for Exterior Sculpture

Although GOLDEN uses only the most permanent pigments available within each chemical classification, we have compiled this list of the best pigment choices for use on an exterior mural. Application of isolation coats and MSA Varnish layers is highly recommended.

BEST PIGMENTS - The most stable GOLDEN colors for exterior use.

  • Bismuth Vanadate Yellow
  • Bone Black
  • Burnt Sienna
  • Burnt Umber Light
  • Burnt Umber
  • Carbon Black
  • Chromium Oxide Green
  • Chromium Oxide Green Dark
  • Cobalt Blue
  • Cobalt Green
  • Cobalt Teal
  • Cobalt Titanate Green
  • Cobalt Turquois
  • Graphite Gray
  • Iridescent and Interference Colors
  • Manganese Blue Hue
  • Mars Black
  • Mars Yellow
  • Neutral Grays
  • Phthalo Blue GS
  • Phthalo Blue RS
  • Phthalo Green BS
  • Phthalo Green YS
  • Primary Cyan
  • Pyrrole Orange
  • Pyrrole Red
  • Pyrrole Red Dark
  • Pyrrole Red Light
  • Raw Sienna
  • Raw Umber
  • Red Oxide
  • Terre Verte Hue
  • Titan Buff
  • Titanate Yellow
  • Transparent Brown Iron Oxide
  • Transparent Red Iron Oxide
  • Transparent Yellow Iron Oxide
  • Titanium White
  • Van Dyke Brown Hue
  • Violet Oxide
  • Yellow Oxide
  • Zinc White

GOOD PIGMENTS - Stable colors, but avoid thin layers or glazes for minimal color shift.

  • Cerulean Blue
  • Cerulean Blue Deep
  • Naples Yellow Hue
  • Turquois (Phthalo)
  • Diarylide Yellow
  • Hansa Yellow Opaque
  • Quinacridone Red

Special Application Requirements

Some artists have had questions about using materials other than artist products for applications ranging from imbedding objects in acrylic gels, riveting metal platelets, creating unusual textures, and unique paper and fabric collage applications. Most of these applications can be done with GOLDEN Gels and Mediums (most commonly using Soft Gel Gloss as a glue); however, certain objects should be attached with more commercially acceptable methods. 2part epoxy glues are best for joining nonporous materials together. Acrylics dry from evaporation, and thus would not be acceptable for materials that did not allow some airflow or have some porosity to them. Contact the GOLDEN Technical Support Department if you require some specific recommendations.

Thick layers of gel mediums and paints require a minimum of 48 hours to dry. Humidity, temperature and airflow are important factors for the drying of acrylics. Be sure to allow for this curing process before final varnishes are applied, as trapped moisture and other additives can be the cause for early delamination.


Clearcoat/Sealing Information

Possible Topcoating Products

The best clear coats in regard to durability are the 2part automotive grade urethanes. These products will have the best weather and marring resistance. Unless the artist has the proper spray equipment, respirators, and adequate spraying space, we suggest consulting a local automotive body repair shop and contracting them to apply this kind of product.

Creating a test panel made from the exact materials that will be used on the fiberglass sculpture is important so the shop can understand what they are asked to do. They can clearcoat the sample prior to the artwork and both you and the sprayer will have a better understanding of the application requirements. Outdoor grade 1part polyurethanes may also be considered for this application; however, they have been known to yellow after application. They may also chip or peel off earlier than the automotive urethane. Other kinds of varnishes such as lacquers, acrylic enamels and epoxies may also be used; however, we cannot offer any suggestions, as we have not completed enough compatibility testing or research for this application.

If a twopart urethane or other acceptable topcoat can not be applied, a secondary option might be GOLDEN's Hard MSA Varnish (with UVLS). However, this varnish is not waterproof and areas where standing water can collect will be prone to blistering and potential delamination from moisture penetration. It is also not recommended where heavy use is anticipated, such as carousel animals or benches. Hard MSA Varnish is a clear, mineral spiritbased acrylic coating that offers Ultraviolet light protection. While removable for cleaning and restoration purposes, Hard MSA Varnish is not readily resoluble in mineral spirits, so stronger aromatic solvents will likely be required (like toluene). It is available in Gloss, Satin and Matte finishes, all of which are intermixable. It is recommended to avoid using mixtures of Satin and Matte, or Matte alone for an outdoor application, as these finishes are more likely to retain dirt and dust. Additionally, they are more susceptible to marring if rubbed, and for these sculptures, chances are high that the public will want to touch and even climb on these objects. We suggest consulting the GOLDEN Hard MSA Varnish literature for information about isolation coats, thinning and other key information.



We hope this information helps artists to achieve long lasting, durable, outdoor fiberglass sculptures, and will encourage, rather than stifle, their creativity. You may have read about some GOLDEN (and other manufacturers) products you are unfamiliar with in the preceding text.

The above information is based on research and testing done by Golden Artist Colors, Inc., and is provided as a basis for understanding the potential uses of the products mentioned. Due to the numerous variables in methods, materials and conditions of producing art, Golden Artist Colors, Inc. cannot be sure the product will be right for you. Therefore, we urge product users to test each application to ensure all individual project requirements are met.