Working with Gelcoats

The Guide for your Production Department

Overview of Working with Gelcoats

The Way to a Better Surface!

Everything you should know about working with gelcoats can be found here in this compact overview.

It’s best to print this guide out immediately and hang it up in your production department. Step by step and with simple graphics, this is an explanation of how to achieve a better gelcoat surface. 


Working with gelcoats


Gelcoat Application

For high-gloss Surfaces

Choosing the right gelcoat or topcoat is crucial for the final properties of fibre-reinforced and cast moulded parts. So quality comes first here!


Material required
Mould, gelcoat, peroxide, brush or cup gun, airless system

Useful accessories
Adhesive tape, layer thickness gauge, personal protective equipment

Working with gelcoats is not difficult. But you should follow a few basic rules. Remember that the gelcoat is the visible side of the component that gives it its colour. Any defects are easy to spot. The gelcoat also serves as protection for the supporting laminate (against moisture, UV radiation, chemicals and abrasion).
The following rules should therefore be followed to achieve the best possible results:
1. Temperature: No lower than 15°C, ideally between 18 and 23°C
2. Layer thickness: Between 500 und 700?m
3. Peroxide: Usually MEKP medium reactive, between 1.5 – 2.5%
Processing methods
1. Brushing on
Recommended for smaller components up to 0.5 m². Usually two layers are applied, with curing in between. This is necessary to achieve the required layer thickness and to prevent any brush marks from showing through.
2. Spraying
Recommended for components larger than 0.5 m². We recommend application in two layers. The first layer with a layer thickness of approx. 150 ?m. Then please wait approx. 90 sec. for de-airing of the gelcoat. The risk of pores will be minimised. The second layer is sprayed on to achieve a total layer thickness of 500 to 700?m (except for specialist products, e.g. fire-retardant applications. Follow the instructions on the technical information sheets). The spraying distance should be between 0.4 m and 0.7 m.
After applying the gelcoat, wait approx. 45 – 60 minutes, but no longer than 6 hours, before applying the laminate. Complete curing of the gelcoat can be checked with the so-called “squeak test”. Carefully rub your finger over the gelcoat surface, applying light pressure. If curing is complete, you will hear a slight squeaking sound.
3. Machine technology
For smaller components (up to 10 m²) and/or only occasional spray applications, we recommend BÜFA®-Tec GSU ES1. For larger components up to 50 m², we recommend
the BÜFA®-Tec GSU Delta 5.5; for even larger components, we advise using the BÜFA®-Tec GSU Sigma 6
4. Troubleshooting
Typical fault patterns include elephant skin, pores, glass fibre showing through and pre-demoulding.

If you have any questions, please feel free to send us an email or give us a call.
To choose a suitable spraying system, please contact Mr Lars Franke from BÜFA Tec.

Contact form