When people talk about "spray painting gelcoat," they are typically referring to the process of applying gelcoat itself using a spray gun, rather than applying paint over a gelcoat surface. Spraying gelcoat is a common technique used in fiberglass construction and repair to achieve a smooth, even finish. It's a method often used when creating parts from a mold.
Key Aspects of Spraying Gelcoat
Spraying gelcoat requires attention to detail, particularly concerning application location and thickness.
Applying Gelcoat Over a Mold
As highlighted in some instructional resources on the subject, spraying gelcoat is frequently done over a mold like this when fabricating fiberglass parts. Applying it directly to the mold surface allows the gelcoat to become the outer layer of the finished product, taking on the smooth surface of the mold.
Achieving Consistent Thickness
A crucial element in successfully spraying gelcoat is achieving and maintaining consistency in the thickness that you're after. Unlike paint, gelcoat is applied relatively thickly and acts as a protective, colored, and structural layer. Consistent thickness ensures uniform curing, appearance, and durability.
Understanding Gelcoat Thickness Problems
The thickness of the applied gelcoat layer is critical. Applying it incorrectly can lead to significant issues:
- Too Thick: As noted in some techniques, you don't want to put it on too thick or you're going to get cracking. Excessive thickness can prevent proper curing, cause internal stress, lead to shrinkage, or result in structural failure like cracking over time.
- Too Thin: Applying gelcoat if you put on too thin can also cause problems. A layer that is too thin may not cure properly, can show the underlying fiberglass texture ("print-through"), provide insufficient UV protection, or lack the desired color depth and durability.
| Thickness Issue | Consequence |
|---|---|
| Too Thick | Cracking, poor curing |
| Too Thin | Print-through, poor UV protection, insufficient durability |
Techniques for Spraying Gelcoat
While specific techniques vary depending on the equipment (like an HVLP spray gun) and the project, the goal is always to apply the gelcoat evenly to achieve the correct wet film thickness, typically measured before curing. This involves using consistent spray passes, maintaining a steady speed and distance from the surface, and ensuring adequate overlap between passes to build up the layer uniformly and achieve the desired consistency in the thickness.
Effective spraying techniques help avoid the pitfalls of applying the gelcoat too thick or too thin, thus preventing issues like cracking and ensuring a durable, high-quality finish.
