Uniform coating (LCP) is a key stage in the recovery of the car, which directly affects the visual perception and durability of body protection. Use of the spray-drill allows you to achieve professional surface quality, which is not available when working with aerosol cans or brush, creating a perfectly smooth "mirror" layer.
However, the tool itself does not guarantee an excellent result, if you do not know the intricacies of preparing the mixture and setting up the equipment. Beginners often face sweats, shaking or dry spray, not realizing that the reason lies in the wrong ratio of pressure and viscosity.
In this article, we will take a detailed look at the entire process, from the selection of compressor parameters to the finish polishing, so that you can get the job done qualitatively the first time.
Selection and preparation of equipment
The foundation of quality painting is properly selected compressorIt is capable of producing the required volume of air continuously. To work with modern spray guns HVLP (High Volume Low Pressure) requires not just high pressure, but a large output, measured in liters per minute.
If the compressor receiver is too small, the pressure will drop when the trigger is opened, which will lead to an uneven torch and the appearance of stripes on the body. The optimal choice for garage conditions is considered to be a unit with a receiver of 50 liters and a capacity of at least 250-300 liters per minute.
A critical element of the chain is the air preparation system, including a moisture separator and a gearbox. Getting even microscopic drops of oil or water in the paint is fatal for coating, causing craters and detachment, so the presence of a quality filter-water separator is mandatory.
- 🔧 Check the tightness of all hose joints before starting work to avoid pressure surges.
- 💧 Pour the condensate from the compressor receiver before each painting session.
- 🎯 Make sure that the diameter of the spray gun duse corresponds to the type of material applied (base, varnish, soil).
- 🌡️ Work in a room with temperatures between +18 and +22°C for proper polymerization.
⚠️ Warning: Never use direct-pumped home compressors without a receiver to paint your car, as the pulsation of air is guaranteed to spoil the spray torch.
Adjusting the pressure and viscosity of the paint
The two main parameters that determine the quality of the torch are the pressure at the outlet of the handle of the spray gun and the viscosity of the paint material. The pressure is usually adjusted in the range of 1.5 to 2.5 atmospheres, but the exact value depends on the recommendations of the paint manufacturer and the sprayer model.
To measure the pressure directly at the time of spraying, a special pressure gauge with a remote scale is used, which is connected to the handle of the pistol. If you adjust the pressure on the compressor gearbox "by eye", then the losses in the hose can be up to 0.5-0.8 atm, which will lead to errors.
The viscosity of the material is measured by a viscometer (DIN-4 funnel) and indicates how easily the liquid flows. Too thick paint will lie "orange peel", and liquid flow vertical stripes, so the diluent is added strictly according to the instructions.
Use measuring rulers and proportioned glasses to accurately mix components, as a deviation of 5-10% can change the cover and drying time.
The tuning process requires a consistent approach: first, the viscosity is exposed, then the pressure is selected, and only after that, a test spraying on the cardboard is carried out. Ignoring any of the steps makes the outcome unpredictable.
Applying technique and hand movement
The correct painting technique is to move the spray gun strictly parallel to the surface of the body at a constant speed. The hand should move from the elbow or shoulder, not just the hand, to keep the same distance to the part (usually 15-20 cm) throughout the passage.
Each subsequent passage should overlap the previous one by about 50-60%, which ensures a uniform distribution of the material without stripes and gaps. Press the trigger before the movement over the part and release after passing the edge to avoid the accumulation of paint at the beginning and end of the strip.
There are several application schemes, but the most common horizontal or vertical sequence of stripes depending on the shape of the element. The main rule is not to stop the movement of the hand with the trigger pressed, otherwise a drop will form, which will have to be removed.
☑️ Checklist before the start of painting
When painting complex reliefs or arches, care must be taken that the axis of the torch is always perpendicular to the painted surface. If you hold the gun at an angle, some of the paint will ricochet, creating a dry fog and an uneven layer.
Table of parameters for different materials
Different types of car enamels require an individual approach to equipment setup. Soils, bases and varnishes have different density and evaporation rate of solvent, which dictates their working conditions.
Below are the averages that serve as a starting point for customization, but always check the technical map of a particular product.
| Materials | Duse diameter (mm) | Pressure (atm) | Viscosity (sec) |
|---|---|---|---|
| Acrylic soil | 1.6 - 1.8 | 3.0 - 4.0 | 18 - 22 |
| Basic enamel | 1.3 - 1.4 | 2.0 - 2.5 | 16 - 18 |
| Acrylic lacquer | 1.3 - 1.5 | 2.0 - 2.5 | 16 - 20 |
| Liquid plastic | 2.5 - 3.0 | 3.5 - 5.0 | 20 - 25 |
Using a smaller diameter duse for thick soils will lead to constant clogging and the need for frequent cleaning, and too large duse for varnish will cause overconsumption of material and the risk of leakage.
Why is it important to maintain viscosity?
If the viscosity is too high, the paint will not have time to spread before drying, forming a large shavel. If it is too low, there will be leaks and loss of gloss effect.
Removal of paint defects
Even experienced painters sometimes face defects, the causes of which are often rooted in a violation of technology or external conditions. Understanding the nature of the defects allows you to quickly eliminate them without completely repainting the element.
One of the most common defects is shashadrane ("orange peel"), which occurs due to too rapid drying of the solvent, high pressure or improper viscosity. To correct mild shashaven is often enough polishing after complete polymerization, but severe cases require sanding and re-application.
The leaks are formed when too slow movement of the hand, close location of the gun to the surface or excessive overlapping of the strips. Fresh flow can be carefully collected with a blade or needle, but the frozen will have to be removed by grinding.
- 🌫️ Dry fog (dust on the surface) occurs when working in a dusty room or at too high pressure, breaking the paint into dust.
- 💧 Craters (fish eye) are caused by the ingress of silicone, oil or water to the surface before or during painting.
- 🎨 The swelling is often caused by an incorrect layer thickness or a violation of the interlayer drying time.
- 🌡️ Boiling of paint occurs if too thick a layer is applied or a solvent is used too fast at high temperature.
⚠️ Warning: Trying to polish fresh varnish in the first 24 hours after painting will lead to clouding and the appearance of holograms, as the material has not yet gained final hardness.
Tool care and safety
The service life of the spray gun and the quality of its work directly depend on timely and thorough washing. Residues of paint, frozen in the channels or on the needle, violate the geometry of the torch and can get to the painted surface at the next work.
Washing should be performed immediately after completion of work, using the appropriate solvent. Do not leave the tool with the chemistry poured inside for a long time, as this can damage the sealing cuffs.
Safety issues when working with auto repair varnishes and solvents are in the first place, since the pairs of these substances are toxic and flammable. The use of a quality charcoal respirator and protective suit is a requirement, not a recommendation.
The quality of painting depends on 80% of the surface preparation and cleanliness in the room, and only 20% on the skills of the master and equipment.
The room should be equipped with ventilation to remove the mist of paint and solvent vapors. Sparking from power tools or static electricity in the painting area is unacceptable due to the high concentration of flammable vapors.
How often should I change the filters in the spray gun?
Filters in the handle and tank of the spray gun should be checked before each refueling. If the net shows contamination or it is deformed, the filter must be replaced or thoroughly washed with a solvent with purge. A clogged filter creates resistance to the flow, which changes the characteristics of the torch.
Can I paint in the winter in an unheated garage?
It is not recommended to paint at a temperature below +15 ° C. At low temperatures, the paint loses fluidity, spreads worse, and drying time increases significantly, which increases the risk of dust settling. In addition, moisture condensation from the air on cold metal is possible.
What if the paint started to dry in the duo during work?
It is necessary to immediately stop spraying, wipe the nose of the spray gun with a napkin moistened with solvent, and blow the tool. If the problem recurs, it means that the room is too hot or a solvent is used too quickly, which should be replaced with a "slow one".