Restoration of paintwork (paint and varnish) is one of the most complex and important processes in body repair, requiring not only high-quality equipment, but also a deep understanding of the chemical properties of materials. Painting of body elements often becomes necessary after an accident, the appearance of pockets of corrosion, or simply due to the natural fading of pigment under the influence of ultraviolet radiation. It is the quality of the work that determines how long the new layer will protect the metal from an aggressive external environment and maintain its aesthetic appeal.
Many owners mistakenly believe that it is enough to simply apply paint to the damaged area, but without careful preparation and adherence to technological instructions, the result will be disastrous. Modern materials such as base enamel and two-component varnishes require precise adherence to mixing proportions and drying temperature conditions. In this article, we will analyze in detail all stages of the process so that you understand what you are paying money for in the service or what you need to do yourself.
High-quality painting is always a balance between drying speed, adhesion (adhesion) of materials and the final appearance. A critical factor is absolute cleanliness in the spray booth, as even a microscopic speck of dust can ruin the entire result. Let's look at what this complex technological process consists of and what tools are required to implement it.
Diagnosis of damage and selection of repair technology
Before taking active action, it is necessary to conduct a thorough inspection of the damaged element. It is not always necessary to completely repaint the part; sometimes local repairs or even polishing are enough. Cleavage depth determines the strategy: if only the varnish is damaged, the problem is solved by polishing, and if the metal is already visible, a comprehensive restoration with priming will be required.
It is important to determine the type of paint used in the factory. This can be acrylic, metallics, mother-of-pearl or special coatings like “chameleon”. Each type automotive enamel requires its own approach to application and dilution. For example, metallics are more difficult to apply due to the risk of apples-eye stains, while acrylics are more forgiving but require a high-quality varnish for shine.
⚠️ Warning: Never attempt to paint over rust without completely removing it. Corrosion will develop under the new coat of paint, blistering it from the inside over several months.
Computer analysis is used to accurately select colors, but even this does not provide a 100% guarantee due to the fading of the old paintwork. Therefore it is often required shading (transition) to adjacent elements to visually smooth out the difference in shades. This is especially true for red, yellow and black colors, which are the most sensitive to change.
Necessary materials and equipment for painting
The quality of the result directly depends on the materials used. Cheap solvents can cause cloudy varnish or poor enamel flow. You will need to purchase degreaser, which does not leave a greasy film, high-quality sandpaper of different grits (from P80 to P2000) and sticky wipes to remove dust.
The basic set of materials includes a filler primer, base enamel (color) and a two-component varnish with a hardener. Also spray gun with a correctly selected nozzle: 1.3–1.4 mm is usually used for the base, and 1.6–1.8 mm for thick soils. The compressor must provide stable pressure and air volume so that the spray pattern is uniform.
- 🎨 HVLP spray gun — provides high material transfer and saves paint by minimizing fog.
- 🌬️ Compressor - must have a receiver with a volume of at least 50 liters for stable operation without pressure pulsation.
- 🧤 Protective equipment — a respirator with carbon filters, gloves and a painting suit are required for health safety.
Don’t forget about consumables: masking tape, covering film or paper, polishing wheels of varying hardness. All these components form the final cost of the work. Using professional chemical brands like Mipa, Motip or Novol significantly increases the chances of success, especially for beginners.
Buy solvent of the same brand as the paint material. Mixing chemicals from different manufacturers can lead to unpredictable reactions and coating defects.
Surface preparation: cleaning and priming
Preparation takes up to 70% of the entire process and is the foundation for the durability of the coating. First, the part is washed, then the old paintwork is removed to the metal or to a durable layer of soil. To remove corrosion, use a rust converter, mechanical cleaning or sandblasting.
After cleaning, the surface must be degreased. Application acid soil (phosphating) onto bare metal creates a chemical bond and prevents rust from reappearing. After it dries, an acrylic filler primer is applied, which evens out small scratches and creates an ideal base for the paint.
Sequence of soil grinding:1. Primary grinding: P240-P320 (for leveling)
2. Second stage: P400-P500 (under the base)
3. Finishing: P600-P800 (for complex colors)
The primer is dried according to the instructions, then sanded. It is important not to rub the primer layer down to the metal, especially on the edges and ribs. If this happens, the area needs to be primed again. Before applying the paint, thoroughly blow the surface with compressed air and wipe it with a sticky cloth.
☑️ Control of surface preparation
Technology of applying paints and varnishes
The most important stage is applying paint. The room must be free of dust, the temperature of the air and the surface of the part should be about 20°C. Base enamel applied in 2-3 layers with interlayer drying (exposure) for 10-15 minutes. The first layer is made “dusty” (thin) to ensure adhesion, the subsequent ones are wetter and more opaque.
After the base has dried (it should become matte), apply varnish. Varnish is a protective layer that gives color depth and gloss. It is usually applied in 2 layers: the first thin, the second wet, glossy. It is important not to overfill the varnish, otherwise drips may form that are difficult to remove by polishing.
| Parameter | Base enamel | Acrylic varnish | Soil filler |
|---|---|---|---|
| Viscosity | Low | Medium/High | High |
| Number of layers | 2-3 layers | 2 layers | 2-3 layers |
| Drying between layers | 10-15 min | 15-20 min | 10-20 min |
| Finish | Matte | Glossy | Matte |
When working with metallic paints (metallics) it is critical to maintain the same distance to the surface and the speed of passage of the spray gun. Changing these parameters will result in different colors and spots. Movements should be smooth, perpendicular to the surface, with a torch overlap of 50%.
⚠️ Attention: Do not try to speed up the drying of the base with a hairdryer or heat. This can lead to boiling of the solvent deep in the layer and the appearance of bubbles after applying the varnish.
What to do if varnish drips?
If you notice a drip immediately after application, do not touch it. Let the varnish dry completely (it is better to leave it for a day). Then carefully cut with a sharp blade or sand with P1000-P1200 abrasive to the level of the base coat and polish.
Drying and polymerization of the coating
Proper drying determines the hardness and durability of the coating. Natural drying at room temperature takes a lot of time (full polymerization takes up to 7-14 days), so in service conditions they use infrared lamps or drying in a chamber. Temperature usually 60°C for 30-40 minutes.
When using IR drying, it is important to set the distance to the part correctly so as not to boil the solvent. Infrared radiation penetrates deep into the layers, ensuring uniform drying. This is especially important for plastic elements, which can become deformed due to uneven heating.
After drying, the part should cool naturally. It is not recommended to immediately expose it to loads or washing. Full chemical resistance of the varnish is achieved only after final polymerization, so it is better to wash the car carefully for the first couple of weeks, without aggressive chemicals or abrasives.
Proper drying at the right temperature makes the coating hard and scratch-resistant, while under-dried varnish will remain soft and quickly lose its shine.
Finishing: polishing and removing defects
Even under ideal conditions, minor defects may remain on the surface: “shagreen” (orange peel), specks of dust or micro-scratches. To eliminate them, it is carried out abrasive polishing. The process begins with the selection of an abrasive paste and a polishing wheel of appropriate hardness.
First, use a hard wheel and an abrasive paste (cutting compound) to remove shagreen. The movements of the machine should be progressive, without strong pressure, so as not to overheat the varnish. After removing the main mark, the surface is transferred to a softer wheel and finishing paste to restore gloss.
- 🔴 Hard Circle - for the initial removal of shagreen and deep scratches.
- 🟡 Middle circle — for intermediate processing and removal of holograms.
- ⚪ Soft circle - for finishing polishing and creating a deep mirror shine.
The final step may be the application of protective wax or ceramic composition. This will close the micropores in the varnish and make further car care easier. A properly polished element cannot be distinguished from the factory coating by touch or by sight.
How to understand that shagreen is completely removed?
Inspect the surface under a bright light source (flaw detection). If the reflection is clear, without ripples or blur, and the surface is smooth to the touch like glass, the shagreen has been removed. Use gloss to check.
Is it possible to paint a part without removing it from the car?
Yes, it's called transition painting. However, it requires great skill to properly blend the edges of the new paint with the old. The removed part allows you to paint the ends and avoid paint getting on adjacent elements.
How long does it take for paint to dry before polishing?
The minimum time is 24 hours with natural drying. If forced drying at 60°C was used, polishing can be done 1-2 hours after the part has cooled. Early polishing will result in varnish failures.
Why did a matte effect appear after painting?
This can be caused by high humidity in the room, using a fast solvent in cold weather, or insufficient pressure in the spray gun. In mild cases, polishing helps, in severe cases, repainting helps.