Duratec 904-001 Hi-Gloss Additive

Duratec 904-001 Benefits

• Air-cured surface: Produces a hard, sandable finish without wax or PVA.
• Improved gloss: Helps eliminate dull repair edges and supports a smooth polished finish.
• Better flow and leveling: Thins compatible gelcoat to help reduce orange peel and improve spray characteristics.
• Easier finishing: Creates a smooth surface that is easier to sand, compound and polish.
• Reduced tooling porosity: Improves air release when added to tooling gelcoat.
• Versatile use: Suitable for gelcoat repair, resurfacing, plugs, patterns and tooling gelcoat upgrades.

Recommended Mix Ratios

Catalyst: Both the gelcoat and Duratec require catalyst. Hawkeye Industries recommends catalyzing the complete blend with a full-strength MEKP catalyst at a 2% mix ratio. Accurately measure the catalyst by weight with a scale or by volume with an MEKP dispenser, and mix only the amount that can be sprayed within the gelcoat's working time.

Preparation and Application

1. Confirm conditions. Apply at 64°F or warmer. Cooler temperatures extend cure time.
2. Prepare the surface. Sand the repair or resurfacing area with 180 grit. Remove failed or cracked gelcoat, grind cracks to the laminate and bevel the surrounding edge. Repair any damaged laminate before coating.
3. Test compatibility. Mix a small cup test with the selected gelcoat and verify gel time and final cure before spraying.
4. Choose the blend. Use the 50/50 blend for normal repairs and resurfacing when opacity is not a concern. Use the 25/75 blend or unmodified gelcoat build coats when working with dark colors that require greater hide.
5. Catalyze the full blend. Add full-strength MEKP at 2% and mix thoroughly.
6. Spray controlled passes. Keep each pass within the sticky or thumbprint stage so the coats bond properly. Allow out-gassing between passes.

50/50 repair blend: Spray at least two passes and build approximately 8 mils or more as needed to match the surrounding surface. For full-surface resurfacing, build at least 18 mils overall in 5-7 mil passes, allowing out-gassing between passes.

25/75 higher-hide blend: Spray three to four passes to build approximately 12-15 mils, allowing at least two minutes between passes. Do not allow the coating to cure beyond the sticky or thumbprint stage between coats.

Spray Tip Guidance

Duratec 904-001 lowers the viscosity of gelcoat. A thinner blend may flow well and resist orange peel with a spray tip of 2.0 mm or smaller, while a thicker material may require a 2.5 mm or larger tip to avoid clogging and poor atomization. Select the final tip size by testing the specific gelcoat, blend ratio and spray equipment.

Below-Waterline Use

Duratec 904-001 may be used wherever the selected gelcoat is suitable. For areas exposed to water for extended periods, Hawkeye Industries recommends a 50/50 Duratec-to-gelcoat blend on the final passes, building at least 10 mils of closed, fully cured surface. Duratec 1799-006 Vinyl Ester Primer is recommended during surface preparation, especially below the waterline.

Sanding, Compounding and Polishing

Begin sanding only after the surface has cured enough that it does not clog the abrasive. Start with the finest practical grit; a well-sprayed surface may allow a 400-grit starting point. Progress through finer grits such as 400, 600, 800 and 1000 before compounding and polishing with products formulated for gelcoat.

After the initial sanding opens the surface, wait at least eight hours before polishing. This open time allows styrene release and supports full cure.

Product Properties

Cure-Time Expectations

Cure time depends on the gelcoat manufacturer and color, ambient temperature, humidity, catalyst ratio, blend ratio and film thickness. A surface may become sandable in approximately two to four hours under favorable conditions, but some applications can require more than 24 hours for full cure. Avoid spraying below 64°F and use controlled warmth near the part when possible.

Frequently Asked Questions

What does Duratec Hi-Gloss Additive do?

Duratec 904-001 converts compatible gelcoat to an air-cure blend that flows and levels more like paint. It creates a hard, sandable surface without wax or PVA and helps produce a smooth, polished gelcoat repair.

What is the mixing ratio for Duratec 904-001 and gelcoat?

Use a 50/50 blend of one part Duratec to one part gelcoat for most repairs where opacity is not a concern. Use one part Duratec to three parts gelcoat when greater color hide is needed. Tooling gelcoat may be upgraded with 10-25% Duratec.

Does Duratec 904-001 need MEKP catalyst?

Yes. Both the gelcoat and Duratec require catalyst. The manufacturer recommends catalyzing the complete blend with full-strength MEKP at 2%.

Can Duratec Hi-Gloss Additive be used below the waterline?

It may be used where the selected gelcoat is suitable. For prolonged water exposure, the manufacturer recommends using a 50/50 blend on the final passes and building at least 10 mils of closed, fully cured surface.

How long should Duratec cure before sanding and polishing?

The surface may become sandable in approximately two to four hours, although conditions and gelcoat chemistry can extend the cure. After initial sanding, leave the surface open for at least eight hours before polishing.