Hand Laminating & Spray-Up Technical Support

Hand laminating and spray-up are two of the most common open molding processes used in fiberglass fabrication. While both methods rely on similar materials, success depends on understanding the differences in application technique, resin behavior, and process control.

At Fiberglass Florida, we provide technical support to help fabricators, repair yards, and builders choose the right laminating method and materials for their project — and apply them correctly the first time.

If you need help selecting resins, setting up a process, or troubleshooting lamination issues, contact our technical team by calling us or emailing orders@fiberglassflorida.com.

What Is Hand Laminating?

Hand laminating, also known as hand lay-up, is an open molding process where fiberglass reinforcement is placed into a mold and manually saturated with resin using rollers, brushes, or spreaders.

This method offers excellent control over laminate placement and is commonly used for boat repair, custom fabrication, tooling, and low- to medium-volume production.

Key Characteristics of Hand Laminating

• Fiberglass reinforcement is placed dry into the mold
• Resin is applied manually and worked into the fibers
• Air is removed using laminating rollers
• Laminate thickness and fiber orientation are carefully controlled

Hand Laminating Resin Selection

Resins used for hand laminating must wet out fiberglass efficiently while maintaining enough body to prevent excessive sag or drainage on vertical surfaces.

Common resin choices include:

• Polyester Laminating Resins for general-purpose fabrication and repair
• Vinyl Ester Laminating Resins for improved strength, water resistance, and corrosion resistance

Resin working time, thixotropy, and cure behavior should be matched to part size, laminate thickness, and ambient conditions.

Hand Laminating Best Practices

• Prepare molds or surfaces thoroughly before lamination
• Pre-cut fiberglass reinforcement for efficient placement
• Apply resin evenly and avoid flooding the laminate
• Use proper rollers to remove air and compact fibers
• Control laminate thickness to manage heat buildup
• Allow proper cure before trimming or secondary bonding

What Is Spray-Up?

Spray-up is an open molding process where chopped fiberglass roving and catalyzed resin are sprayed simultaneously into a mold using a chopper gun system.

Spray-up is commonly used for larger parts and higher production volumes where speed and material efficiency are important.

Key Characteristics of Spray-Up

• Continuous roving is chopped and sprayed with resin
• Material is applied quickly over large surface areas
• Roll-out is required to remove air and compact fibers
• Laminate thickness is built up in controlled passes

Spray-Up Resin Selection

Spray-up resins are formulated to atomize properly through chopper gun systems while maintaining wet-out and sag control.

Key resin characteristics include:

• Consistent viscosity for reliable spraying
• Balanced thixotropy to reduce sag after application
• Controlled gel time to allow roll-out and consolidation
• Predictable cure and exotherm behavior

Polyester and vinyl ester resins can both be used for spray-up, depending on performance requirements and environmental exposure.

Spray-Up Best Practices

• Maintain proper gun setup and catalyst calibration
• Apply material in even, overlapping passes
• Roll each pass thoroughly to remove trapped air
• Avoid excessive build-up in a single pass
• Monitor ambient temperature and humidity

Hand Laminating vs Spray-Up

Choosing between hand laminating and spray-up depends on part design, production volume, and performance requirements.

• Hand Laminating: Greater control, higher fiber orientation accuracy, ideal for repairs, tooling, and custom work
• Spray-Up: Faster coverage, efficient for large parts and production runs, requires careful roll-out and process control

Common Lamination Issues We Help Solve

• Poor fiberglass wet-out
• Excessive air entrapment or voids
• Resin sag or drainage on vertical surfaces
• Inconsistent cure or slow Barcol development
• Excessive heat buildup or print-through

Need Help With Hand Laminating or Spray-Up?

If you’re selecting a lamination method, choosing a resin, or troubleshooting an open molding process, our technical team is here to help.

Email: orders@fiberglassflorida.com
Call us for expert guidance before you begin

Fiberglass Florida — practical open molding support, trusted laminating materials, and real-world experience.