Painting the body of a car is not just a color application, but the creation of a multi-layer protective pie, where each level performs its function. When it comes to polymerMany motorists are wondering: is it necessary to cover it with varnish or can it be left as it is? Technically, acrylic is the finishing coating itself, but applying varnish over it drastically changes the performance and appearance of the part.
The depth of color, resistance to chemical reagents and the possibility of polishing - all these advantages are opened after varnishing. In this article, we will discuss how to paint acrylic under varnish on a car to avoid detachments, matte spots and other defects that can negate all work.
The process requires strict adherence to timing and temperature regimes, as chemical reactions between layers are critical. An error in choosing the time of applying the varnish can lead to the fact that the coating will become cloudy or, conversely, the solvent will burn through the base.
Physics of the process: why varnish the acrylic base
Acrylic paint, or "acrylic", is a pigmented composition that, after the evaporation of the solvent and the reaction of the hardener, forms a strong matte or semi-matte film. However, this film, although persistent, does not have the inertia to the external environment, which gives a special varnish. Lacquer creates a solid transparent shell, taking on the impact of gravel, exposure to ultraviolet and aggressive chemistry on the sinks.
In addition to the protective function, the varnish is responsible for aesthetics. Without it, the color looks flat and dry, especially if it is complex shades like “metallic” or “pearl”. Lacquer saturates the color, making it deep and voluminous. It is important to understand that not all acrylic paints are the same: there are bases that require mandatory varnishing (1K or 2K base for varnish), and enamels that already contain components for gloss.
If you plan to polish the body in the future to eliminate scratches, then a layer of varnish is simply necessary. The acrylic base itself is extremely risky to polish because of its softness and thinness of the layer - you can easily wipe to the ground.
⚠️ Warning: Never apply varnish to acrylic paint that has dried for more than 24 hours without special preparation. The surface will become too smooth, and the adhesion of the varnish will be broken, which will lead to peeling with a "stocking" in the future.
Required tools and materials for the job
The quality of the result depends on what you do. The use of cheap solvents or spray guns with worn-out duzes is guaranteed to lead to defects. You'll need to work. spray-shoot with a duse of 1.3-1.4 mm for the base and 1.4-1.6 mm for varnish. The compressor must provide stable pressure without pulsation, otherwise the torch will "spit".
The most important element is the air conditioning system. The moisture separator should be of high quality, since even microscopic drops of oil caught in the paint will create craters that cannot be removed without repainting. Also, you can not do without a degreasing agent, sticky wipes and a properly selected solvent.
The temperature in the paint chamber or garage should be stable. Cold air will slow the evaporation of the solvent, causing stains, and too hot will accelerate the drying, creating an “orange peel”.
- 🎨 Acrylic base (Selected by body code) and the corresponding hardener.
- ✨ Car lacquer (HS is dry residue, or MS is average dry residue) with a hardener.
- 💧 Solvent (Dilluent) for the base, selected by the temperature in the room (fast, medium or slow).
- 🧹 Degreasing, antistatic and sticky wipes to remove dust.
- 🛡️ PPE: respirator with carbon filters, gloves, protective suit.
Choosing a solvent is not a small thing. If the garage is cool (about +18°C), use a “fast” diluent to keep the paint from flowing. In the heat (+25 ° C and above) a "slow" solvent is required, otherwise the base will dry on the fly, without having time to spread, and lie down "stepping".
Surface preparation technology and application of the base
Before painting, the surface must be perfectly prepared. This means that the filler soil is polished, the risks are primed, and the surface is defatted. Apply an acrylic base on glossy old varnish or greasy spots can not - the coating will fall off.
The process of applying the base is carried out in several thin layers. The first layer, often called “fog” or “slinging”, is applied from a distance of 25–30 cm in rapid movements. It does not have to cover the surface completely, its task is to create an adhesive layer. After this, a technological pause (usually 10-15 minutes) is followed for the evaporation of the solvent.
The second and third layers are applied more wetly, covering the surface by 50-70%. Here it is important to monitor the torch: it should be smooth, without tears. If you see the paint start to boil or bubble, it means the layer is too thick or the solvent is too fast for the current temperature.
☑️ Checklist before applying varnish
It is critical to let the base dry before varnishing. Acrylic should be matte. If you apply the varnish on a glossy, undried base, the solvent from the varnish will "lift" the paint, and it will shrivel. Drying time depends on the manufacturer of the materials and temperature, but the average is 20 to 40 minutes.
Material compatibility and solvent table
One of the main problems with painting is chemical incompatibility. Aggressive solvents in the varnish can react with a dry base. Therefore, manufacturers often recommend using products of the same system or proven compatible analogues.
Below is a table of the approximate drying time of the acrylic base before applying the varnish at different temperatures. This data is relevant to most standard systems (e.g., Mobihel, Vika, PPG).
| Air temperature | Type of base solvent | Min. drying-time | Max. varnishing | Risk of defects |
|---|---|---|---|---|
| +18...+20°C | Normal (Standard) | 30 minutes | 12 hours. | Medium (possible shaking) |
| +22...+25°C | Slow (Slow) | 20 minutes | 24 hours. | Low (ideal conditions) |
| +15...+17°C | Fast (Fast) | 40 minutes | 6 hours | High (dust, smudges) |
| Above +25°C | Very slow. | 15 minutes | 4 hours | Critical (boiling) |
Note the column "Max". time before varnishing”. If you overstay the base for more than a day, it must be treated with scotch bright (grey or white, P800-P1200) and again degrease before varnishing, otherwise the varnish will not stick.
What to do if the base is too dry?
If more than 24 hours have passed since the base was applied, the surface must be treated with a soft abrasive (scotch bright P1000-P1200) with light circular movements. This will create a micro-risk for staining the varnish. After grinding, be sure to blow the part with compressed air and degrease. Apply varnish on a smooth, old base without matting - a guarantee of detachment.
The process of applying varnish: technique and nuances
Applying varnish is the final stage that determines the appearance. The lacquer is applied in two or three layers. The first layer is made thin, "dusty" to create the base and not cause subtexts on the verticals. The movements of the gun should be smooth, with the previous passage overlapping by 50%.
The second layer is applied "on wet", that is, immediately after the first layer has settled a little (after 10-15 minutes). Here it is important to put the polish smoothly, without shaking. If you see that the varnish began to flow, do not immediately try to exfoliate the undertrenchment - it is better to leave it and grind it later. The third layer (if a three-layer system is used or there is little gloss) is applied similarly to the second, but even more carefully.
The pressure on the gun when working with varnish is usually 2.0-2.5 atmosphere at the entrance. Too high pressure will lead to dust (varnish will dry on the fly, creating a rough surface), and too low - to poor spraying and major shaking.
- 🌪️ Keep the gun strictly perpendicular to the surface at a distance of 20-25 cm.
- ⏱️ Observe interlayer drying: the varnish should become matte, but remain sticky.
- 👀 Control the reflection of light: glossy glare should be smooth, without tears.
- 🧪 Use the hardener recommended by the varnish manufacturer (usually 50% or 33%).
⚠️ Warning: Do not try to speed up the drying of the varnish with heat guns in the first 30 minutes. The sharp heating of the surface will lead to boiling of the solvent inside the layer and the formation of bubbles, which will appear only after cooling.
Checking readiness for the next layer: touch the edge of the painted area with your finger (in an inconspicuous place or on the test plate). If the finger is not dirty, but there is a stickiness (as in scotch tape), you can apply the next layer. If the finger gets stained with paint, it's early. If the finger is dry and does not stick – late, you need to grind.
Pollination and elimination of defects after drying
Even professionals rarely get the perfect varnish the first time without dust. After complete polymerization (usually 24 hours, but it is better to give a week for final shrinkage), the surface can be polished. The small dust particles are removed with the abrasive P2000–P2500, followed by polishing with paste.
If there are stains, they can not be touched immediately. Let the varnish dry for at least 24-48 hours. The underspread is then carefully cut by the blade or sanded by the P800–P1000 to the level of the main coating, and the place is polished. A gross mistake is to try to grind fresh varnish, it will just clog up the abrasive and heat up.
For finishing polishing, use a soft-circle machine and a fine abrasive paste. This will bring depth back to the color and remove the micro-risks from grinding. Quality HS-lacquer after polishing gives a mirror shine, indistinguishable from the factory.
The main secret of the perfect varnish is not the technique of application, but the cleanliness in the room and proper drying between the layers. Dust and haste are the main enemies of the glossy effect.
Frequent Mistakes and How to Avoid Them
Beginners often encounter a defect of "matted spots" or "occurrence." This occurs when the varnish is applied to a wet base or in a room with high humidity. The solvent locked in the layer condenses and gives a whitish hue. This is treated only by a complete repainting after thorough drying.
Another problem is “appleness” (multiple). It occurs if the base is applied unevenly: somewhere thicker, somewhere thinner. Lacquer, being transparent, does not hide this defect, but emphasizes it. To avoid this, apply the base with cross movements and control the overlapping of the layers.
Ignoring the instructions on the bank is the way to failure. Different manufacturers use different chemical formulas. Mixing a hardener from one brand with another can lead to the fact that the coating will never dry or curl up into porridge right in the tank.
Can I apply varnish on acrylic if it has been 2 days?
Yes, you can, but only after preliminary preparation. Within two days, the surface was completely polymerized and smooth. You need to wrap the entire detail in a gray scotch bright or abrasive P1000-P1200 to create a risk for adhesion. Then carefully blow, degrease and only then varnish. Without matting, the polish will fall off with film.
How much does the acrylic dry before applying?
The time depends on the temperature and type of solvent. On average, at +20 ° C, it is 20-30 minutes. The main sign of readiness is uniform matting of the surface. If there are glossy spots, then the solvent has not yet gone, and apply lacquer early - there will be a boil.
Do you need soil before acrylic paint?
Acrylic base does not have anticorrosion properties and does not hold well on bare metal. On the metal must be applied acid or epoxy soil, then acrylic filler (soil filler). On the old paint or soil-filler base can be applied directly after grinding and degreasing.
Which is better: HS or MS?
HS (High Solid) - more modern, contains more dry residue, gives a thick layer, a deep gloss and is easier to polish. MS (Medium Solid) is cheaper, but gives a thinner layer and dries faster, which can be a plus for beginners, but a minus for the depth of color. For high-quality painting of the car, it is better to choose HS.