Invisible, but essential – the clear coat

What makes a clear coat special?

The clear coat is a key element of the protection and aesthetics of the painted surface. Its composition includes resins, which are responsible for mechanical and insulating properties, thinners that regulate the application viscosity and flow of the coating, UV stabilisers that protect against ultraviolet radiation, and special additives that improve the durability and appearance of the coating.

Types of clear coats

The main component of clear coats are resins, and their content determines the classification of the clear coat. We distinguish between MS (Medium Solid) clear coats with a resin content of around 40%, HS (High Solid) with 50%, and VHS (Very High Solid) with 60%. The higher the resin content, the better the quality of the coating and the lower the solvent content. MS and HS clear coats use between 2.5% and 20% solvent, while VHS clear coats are often applied without any solvent, which affects their durability and efficiency.

Clear coat regulations

Current regulations impose restrictions on the content of Volatile Organic Compounds (VOCs). In Poland, the maximum permitted thinner content in clear coats is 420g/l for HS and VHS, while MS clear coats, which are classified as speciality clear coats, can contain up to 840g/l. Thanks to these regulations, modern clear coats meet strict ecological and technological standards.

How can the resistance of clear coats be tested?

The UV and weather resistance of clear coats is tested both in laboratories and in natural conditions. Laboratory accelerated ageing tests use devices such as climatic, UV and salt chambers as well as temperature shock chambers. They make it possible to simulate extreme conditions and accelerate the ageing process of coatings. Natural tests are carried out in the harsh climate of southern Florida, where high sunlight, humidity and proximity to the ocean allow for a reliable assessment of the durability of the clear coat in real operating conditions.

Two-component products

Two-component products, a combination of clear coat and hardener, are used for renovation work. The quality of the resulting coating depends on the correct choice of hardener, according to the guidelines of the technical data sheet (TDS). An important component of hardeners are isocyanates, which are responsible for the high durability and resistance of the clear coat. Two-component clear coats are generally recommended due to their durability and excellent coating quality.

Surface preparation before applying the clear coat

The final quality of the coated surface depends on the proper preparation of the substrate. Before applying the clear coat, make sure that the surface is thoroughly cleaned and that the application conditions are right. Apply the base coat, whether conventional or water-based, according to the technical data sheet. Once the solvents have evaporated, apply the clear coat. Make sure the work area is clean to avoid contamination and defects in the coating.

Applying the clear coat

The type of clear coat determines the number of layers needed to achieve the optimal coating thickness. Three layers are needed for an MS clear coat with 20% thinner. High-solids (HS) clear coats require two coats, while a one-and-a-half coat application is sufficient for a vinyl-high-solids (VHS) clear coat, taking into account the appropriate pressure and nozzle diameter of the spray gun. When applying the clear coat, it is crucial to maintain the correct distance between the spray gun and the surface to be coated, usually 15-25 cm, and to guide the spray gun perpendicular to the substrate. This technique has an impact on the durability of the coating and the efficiency of the use of the material. HS and VHS clear coats form an orange peel texture, which increases their scratch resistance, while MS clear coats give a smoother surface.

Clear coat application time

Applying the clear coat at the right time is crucial. If it is applied too soon, the thinner from the base layer can become trapped, resulting in blistering and poor adhesion. If the clear coat is applied too late, the dried base coat will not bond properly with the clear coat, which can lead to flaking. Therefore, it is worth checking the manufacturer's recommendations before application and adjusting the drying time of the base coat to the prevailing conditions.

How fast does it dry?

The curing time of the clear coat depends on the drying method. In natural conditions, it can take several hours, while in a spray booth, the drying time is reduced to several dozen minutes. Modern clear coats, such as CP 2015 HS X-SPEED, allow for complete curing in just five minutes, which significantly reduces repair time and increases work efficiency.

Final effect and trends

The clear coat not only protects the painted surface, but also affects its appearance. It can have a high gloss, which emphasises the depth of colour, or a matt finish, which is becoming increasingly popular in modern automotive design. Matt clear coats are a technological challenge because they must provide the same scratch resistance as glossy coatings. In some cases, it is possible to adjust the degree of mattness by mixing CM 10 matt clear coat with CP 1500 high-gloss clear coat, which allows for a customised end result.

Summary

The clear coat has a protective and decorative function, and its quality and application method are crucial for the durability and aesthetics of the vehicle. Choosing the right type of clear coat, taking care to prepare the surface correctly and using the right application techniques ensure a long-lasting effect and keep the painted surface looking perfect for many years.