How to Polish GRP/Gelcoat Correctly!

Glass-fiber reinforced plastic, often abbreviated as GRP, is a composite material made from plastic and glass fibers. It is also commonly referred to as fiberglass. GRP can be made from thermosetting plastics such as polyester resin (UP) or epoxy resin, as well as from thermoplastic plastics such as polyamide. In the automotive and boat building industry, GRP is usually coated with a protective and visually appealing "gelcoat." The term "gelcoat" refers to a hard paint used as a protective layer on molded parts made of fiber-reinforced plastics like GRP. The gelcoat serves to protect the component from moisture (hydrolysis), UV radiation, and pressure damage by providing a sealing function.

GRP components are commonly found in boats, where even the entire hulls are often made of GRP. GRP is also often used in motorhomes, where the rear and/or front of many models are made of GRP, and sometimes even the entire structure.

Is Polishing GRP & Gelcoat Difficult?

Polishing GRP or gelcoat is usually necessary when components no longer appear visually appealing due to natural wear and tear. This can be identified when the surface loses its shine and appears rather dull, matte, cloudy, or discolored. In addition to the visual defects, the GRP surface becomes much more susceptible to dirt, which can easily adhere and, in some cases, even embed itself into the surface.

Polishing gelcoat-coated GRP surfaces is generally more challenging than polishing a regular vehicle paint because gelcoat, as explained above, is an extremely hard paint. We have our own polishing system using "Ultra-Cut polishing pads in combination with Max-Cut polish," which significantly simplifies the process.

Our Guide to Polishing GRP/Gelcoat:

In this guide, you will find some proven tips and product recommendations that we have already successfully tested for you.

 You will need: A polishing machine (preferably a rotary machine, as it allows you to apply more pressure than an eccentric machine), Ultra Cut polishing pads, Max Cut polish, a soft microfiber cloth.

Step 1: Preparation - Ensure that the GRP surface is clean by removing dirt, dust, or other contaminants. Use a mild detergent and water to thoroughly clean the surface. Then, dry it carefully.

Step 2: Polishing - Attach the polishing pad to the polishing machine and apply a sufficient amount of polish to the pad. [Max Cut polish is a dust-free polish that can be applied for a long time. This is extremely useful for GRP polishing, as most other polishes tend to dust and stick here.] Work on small areas in a cross-motion with the polishing compounds. The areas should not be larger than about 40x40cm to achieve a uniform and reasonable result.

Step 3: Remove and Check Polish - Wipe the surface with a soft microfiber cloth to remove any polishing residues. Examine the surface from different angles to see if the result is satisfactory. If deviations are noticed, simply repeat the process.

Step 4: (Usually only necessary for dark surfaces) If you want a finish for your surface to remove any holograms, etc., you can do this ideally with our Medium polishing pads and Medium polish.

Step 5: Aftercare - After polishing, you can protect the surface with a wax or sealant specifically designed for GRP. Apply the wax or sealant according to the manufacturer's instructions. This will protect the surface and maintain its shine for longer.

TIP: Our Ultra-Shine Quick Detailer is sprayed on and wiped off, providing good preservation. You can also use the product in between to maintain your GRP.

Please note that this guide is very general and may vary depending on specific conditions and products used. It is always advisable to read and follow the instructions of the manufacturer of the products used.