Today, metallic paints are one of the most used and widespread types of car paint, both by manufacturers, with a wide catalogue of metallic and pearl colours, and by users, who seek to provide a differential aesthetics to their vehicles.
Many years ago, the development of innovative acrylic varnishes allowed for great progress in the field of automotive colorimetry. This was the root cause that favoured the emergence of new formulas and types of colours, with metallic colours standing out among them all.
Practically all cars manufactured today have the possibility of being customised in metallic colours.
This great variety of colours increased especially with the arrival of the two-coat finishes to the refinish sector, putting on a second levelsingle-coat finishes, which were used mostly up to then.
What is metallic car paint?
Metallic paint, also known as polychromatic, is a type of paint that has small aluminium particles or other metals added to it in order to produce a shiny effect and depth to the surface, especially emphasised in body contours.
The type, amount, size and colour of the particles can vary to produce all kinds of effects, glows and reflections, providing a brighter finish than any solid paint.
This type of paint usually has a wide variety of shades and colours, and its characteristic brightness is produced by light reflection on the tiny aluminium particles that are mixed with the paint. These particles capture light and reflect it.
The successive coats of the finishing paint emphasise this brightness and depth effect. The metallic colours are integrated in two or three-coat systems and require the final varnish coat to ensure sealing and protectionof the surface.
Advantages and disadvantages of metallic paint
One of the main advantages of metallic paint is that it provides a light protection against small damages and against discolouration caused by UV rays.
The colour variations produced by some metallic colours make small defects more easily concealed. On the other hand, in a solid colour, dents, scratches and other small damages are more visible.
Metallic paint also has an aesthetic function, beautifying the surface by enhancing vehicle contours and lines, providing effects, brightness and luminosity and a selection of colour customisation.
In short, metallic paint significantly increases the visual appeal of a vehicle and its market value.
Its most common disadvantageis related to its cost. Solid colours have a higher cost in the vehicle, which is the result of a more expensive and elaborate manufacturing and application process.
For the professional painter, the reproducibility of some metallic colours also entails greater complexity and difficulty in matching the colours, in addition to higher time required for the repair.
What are the pigments used in metallic paint?
Metallic car paint is classified depending on the type of pigments and particles it is composed of.
These types of pigments are the most common in metallic paint.
They are composed of small aluminium particles, which are responsible for providing the shiny metallic lustre effect. They are usually mixed with absorption pigments (with some transparency to improve the brightness and depth effect).
In order to obtain improved reflection effects, they can also be mixed with other types of particles such as mica. The metallic particles of these pigments come in different sizes and shapes:
- Lenticular aluminium: this is a type of particle that has an oval shape, and whose size can vary, differentiating between thin, medium and thick lenticular aluminium. Due to its shape, the correct direction and coupling of this type of particles during refinishing will be essential to obtain a final flawless finish.
- Irregular aluminium: this is a type of aluminium that has shapes with more irregular edges and different sizes (extra thin, thin, medium, thick and extra thick). Its application and direction is usually simpler than that of lenticular aluminium.
These differences in shape and size, and the direction of the particles during application, will determine the type of effect obtained.
This is why in certain metallic colours you can observe differences in brightness and shade depending on the angle from which you look at the surface, resulting in the so-called “flop effect.”
In order to reduce this effect, some metallic colours include a flop control in their formulation.
Thin aluminium particles are matte, and less problematic than coarse aluminium particles, which are bright and reflect more light. Therefore, colours with a high percentage of coarse aluminium pigments will have a greater “flop effect”.
Pearl pigments contain small particles or scales of the ore in different shapes and sizes.
These particles are mixed with translucent pigments, which means low opacity, which makes it impossible to apply without first mixing it with a solid or metallic colour.
The pearly glow of pearl colours is produced due to the ceramic crystals that make up the paint and are responsible for reflecting and refracting light.
This reflection and refraction of light gives the colour a brightness and depth that is difficult to match even for colours with metallic pigments, and under bright light, the lighter shades become iridescent, producing different colours and shades from various angles, with very striking results. Pearl car paints are even more prone to small marks and defects than paints with metallic pigments.
These types of pigments provide an even sharper visual effect than metallic or pearl pigments.
Its use and application is not very common in the sheet metal and paint sector; they are more used in bodywork customisation.
When painting with special colours, apply a coloured base on the repaired area covering the undercoat before applying the pearl base. Being very transparent pigments, if the percentage of pearl pigments in the colour base is very high, the colour effect obtained will depend on the number of coats applied, the product load or the base colour.
The main special pigments that have a greater presence in the refinishing sector are ColourStream and Xirallic.
ColourStream pigments are formed by silicon dioxide sheets coated with metal oxide, which allow the reflection of different colours and shades. These have a uniform geometry and are developed by manufacturers to provide the body with exclusive visual effects that change shades and colours depending on the angle of vision and impact of light on the surface.
Xirallic pigments are composed of aluminium oxide sheets coated with metal oxides. The formulas containing these types of pigments are called “electric colours”. They provide a crystalline effect with high levels of sparkle and gloss.
Tips on applying metallic colours
Failing to work and prepare the base paints or failing to observe the finish under optimal light source imitating sunlight are some of the reasons that will influence the correct application of metallic colours.
Let us look at some of the keys to follow to correctly apply metallic colours:
- Adapting the use of catalysts and thinners to room temperature and humidity
Adapting the catalysts and thinners according to the temperature will help the metal particles to be directed and coupled correctly.
This is especially relevant when the temperature is high, where the use of slower dilutions and catalysts is recommended, to prevent the appearance of paint defects such as shadows or bursts.
- Applying a final control coat
Applying a final control or anchorage coat will help provide good colour-matching to the finish, and to correctly direct the metallic paint particles.
- Using the blurring technique
In metallic colours, blurring will allow for the part to better integrate with the other adjacent areas, improving colour-matching and minimising the appearance of possible painting defects.
- Correct application technique
A correct application technique makes it easier to match the metallic colour, improving the paint’s covering and the distribution of the particles (to avoid the flop effect).
To do this, it is advisable to direct the gun so that the spray hits the surface regularly, with overlapping coats, distributing the particles evenly.
- Correct colour identification
It is important to identify the size of the metal or the hue of the pearl to assess the shade and make sure that it is the original colour. Once this is done, check the colour version that best matches.
- Correct application of the base
Priming paint plays a key role in colours with two or three-coat finishes. Problems such as excessive product loading or using a priming colour that is not suitable for the finish colour can cause darkening of the metallic colour in some shades.
- Following the product’s technical specifications
In short, as in many other cases, following the manufacturer’s technical specifications (pressure, fan and material flow regulation) will be essential to ensure good metallic colour reproduction.
The correct application of metallic paint can sometimes become a real challenge for professional painters. Some colours like pearl white, metallic grey or pearl blue can cause doubts and problems during the repair process.
Knowing their composition and the most efficient application techniques and advice will help to obtain perfect finishes, free of defects, even in the more complex metallic colours.