How to polish gelcoat
Written by: Vinnie van Rooij
Gelcoats are mostly found when working on boats and jetski’s. It is a specified type of surface that is used in the process of making the shape of the object. a Gelcoat is different then paint. It can be polished, clayed and protected, but slightly different then automobile paint.
What is a gelcoat
Wikipedia has an excellent explanation on this:
Gelcoat is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite. The most common gelcoats are based on epoxy or unsaturated polyester resin chemistry. Gelcoats are modified resins which are applied to moulds in the liquid state. They are cured to form crosslinked polymers and are subsequently backed with composite polymer matrices, often mixtures of polyester resin and fiberglass or epoxy resin with glass.
The manufactured component, when sufficiently cured and removed from the mold, presents the gelcoated surface. This is usually pigmented to provide a coloured, glossy surface which improves the aesthetic appearance of the article, such as a counter made with cultured marble.
Many marine craft and aircraft are manufactured using composite materials with an outer layer of gelcoat, typically 0.5 mm to 0.8 mm (0.02 in to 0.03 in) thick. Gelcoats are designed to be durable, providing resistance to ultraviolet degradation and hydrolysis.
Specialized gelcoats can be used to manufacture the moulds which in turn are used to manufacture components. These require very high levels of durability to overcome the mechanical and thermal stresses encountered during the curing and demoulding processes.
Suitable resin chemistries for the manufacture of gelcoats vary, but the most commonly encountered are unsaturated polyesters or epoxies. Within each of these categories, the resin chemistries are further subdivided.
In addition to any pigment a gelcoat will, if necessary, contain a thixotropic additive to assist its tenacity to vertical portions of the mould whilst it cures.
There are certain differences between a gelcoat and paint. This means that you need a slightly different approach to polish it. It can still be clayed and protected in the same way.
Gelcoat isn’t a type of paint, gelcoat is a colored resin that is sprayed/smeared on a surface and then left to harder (sometimes by light or heat).
How to polish gelcoat
Of all the processes, polishing gelcoat is the one with the biggest difference compared to regular automotive paint. There are a few things to keep in mind when polishing gelcoat.
- Gelcoats like heat and abrasion
- A DA won’t offer you the friction-power you are looking for
- A rotary polisher on a high setting (around 2500-3000 rpm)will do
- Make sure the polish stays moist. Don’t let it dry out or reduce your workarea
- Work in spaces of roughly 2 feet by 2 feet
- You can start with a bit of pressure and then slowly let off when the polish is being worked in
- When using a fine/finishing polish, use a rougher pad then normal to really work it in
- After polishing, apply the wax with a machine. The heat and rubbing speed will help to spread it out
- Remember that your polish needs to stay liquid. Don’t let it dry out. You can keep a spray bottle with water to keep it moist if it is drying out to quick
The end result
A gelcoat can be waxed or sealed by regular products, but there are a few special products that perform best in a very wet environment. Wax is very cost effective, but sealants can perform better for longer. If you have regular access to your boat, then you can use a regular wax. If you only have access to its hull once a year, then a sealant might be a better choice.
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