Introduction
Painting a car is a process where every detail affects the final result. One of the key steps is proper paint thinning. Even the most expensive enamel from PPG or Sikkens will lose its properties if it is diluted with an inappropriate solvent or the proportions are violated. In this article we will look at how to thin car paint depending on its type, application conditions and equipment, and we will also reveal professional secrets that are rarely mentioned in instructions.
Many car owners mistakenly believe that any solvent is suitable for any paint. In practice, the wrong choice leads to loss of shine, prolonged drying, formation of shagreen or even peeling of the coating after a few months. For example, acrylic enamels require slow solvents for high-quality spreading, and “fast” compounds are often used for base paints under varnish. Next is a detailed guide with tables, warnings and life hacks from experts with 10 years of experience.
Types of automotive paints and their features
Before choosing a solvent, you need to understand what kind of paint you are working with. Car enamels are divided into several main categories, each of which requires its own approach to dilution:
- 🔴 Acrylic enamels (for example, Mobihel or Vika) - the most common. Consist of pigment, acrylic resin and hardener. Requires dilution for uniform application with a spray gun.
- 🟡 Base paints for varnish (for example, Standox or Lesonal) - contain only pigment and binder, without a protective layer. They are diluted more aggressively, since varnish is applied on top.
- 🟢 Chalky (matte) paints — used for retro cars or decorative elements. They require special solvents with matting additives.
- 🔵 Alkyd enamels (for example, Duxone) - an outdated type, but still found in budget repairs. Diluted with white spirit or solvent.
- ⚫ Nitro paints - quick-drying, but toxic. Rarely used, diluted with solvent No. 646 or No. 647.
Important: base paints cannot be diluted in the same way as acrylic enamels. The former do not have a hardener, so they dry only due to the evaporation of the solvent. If you overdo it with the thinner, the pigment will lie unevenly, and the varnish will not be able to hide it. For example, for Standox Basecoat the manufacturer recommends a solvent Standox 360 in a ratio of 1:1, whereas for acrylic enamel of the same brand it is 2:1 (paint:solvent).
Types of solvents for automobile paints
Solvents are divided into three main groups based on evaporation rate: fast, average and slow. The choice depends on the ambient temperature, humidity and type of spray gun. Here are the key options:
| Solvent type | Application | Use temperature | Examples of brands |
|---|---|---|---|
| Fast | For cold weather (below +15°C) or base paints | +5°C to +15°C | PPG DX330, Sikkens Autoclear Rapid |
| Medium | Universal for acrylic enamels | +15°C to +25°C | Mobihel 2K Universal, Vika R12 |
| Slow | For hot weather (above +25°C) or large parts | +25°C and above | Lesonal Lackverdünner Langsam, Standox 340 |
| Special | For matte paints or effects (chameleon, metallic) | Depends on the task | Sikkens Autoclear Matte, PPG Deltaclear |
⚠️ Attention: Never use solvent No. 646 for acrylic paints! It aggressively breaks down the binder, leading to loss of adhesion and peeling of the coating after 3-6 months. Only specialized thinners based on butyl acetate or xylene.
Another nuance: some manufacturers (for example, PPG) produce solvents with additives to improve spreading. Such compositions are designated as "High Flow" or "Super Wet". They are more expensive, but reduce paint consumption by 10–15% due to more uniform spraying.
If you are painting a car in a garage without heating in winter, add 5–10% to the solvent isopropyl alcohol (sold in pharmacies). This will speed up evaporation and prevent condensation from forming on fresh paint.
Dilution proportions: how not to make mistakes
Standard dilution ratios are indicated on the paint can, but they are often calculated for ideal conditions (temperature +20°C, humidity 50%). In reality, the proportions need to be adjusted. Here are some basic recommendations:
- 🔘 Acrylic enamel + hardener:
- Paint : Hardener : Solvent =
2:1:0.5(for average conditions). - At +30°C reduce the solvent to
2:1:0.3. - At +10°C increase to
2:1:1.
- Paint : Hardener : Solvent =
- 🔘 Base paint for varnish:
- Paint : Solvent =
1:1or1:0.8(depending on pigmentation). - For metallics and pearls, use
1:0.5to avoid particle settling.
- Paint : Solvent =
- 🔘 Alkyd enamel:
- Paint : Solvent =
3:1(white spirit or solvent).
- Paint : Solvent =
🔹 Critical: When diluted metallics or mother of pearl Never shake the paint before applying! Stir slowly with a stick in a circle so that the pigment does not settle to the bottom, but also does not create bubbles. Shaking leads to an uneven distribution of particles, causing dark and light spots to appear on the body.
Check the room temperature (optimally +18°C–+22°C)|
Use the same brand of thinner as the paint|
Measure proportions by weight (not by eye)|
Filter the paint through a 190-220 micron mesh before pouring into the spray gun|
Carry out a test spray on a test surface -->
How to thin paint for different types of spray guns
The viscosity of paint directly depends on the type of equipment. Spray gun manufacturers indicate the optimal viscosity in seconds by viscometer (usually 18–22 sec at +20°C). Here's how it compares to proportions:
| Spray gun type | Optimal viscosity | Thinning ratio (paint: thinner) | Inlet pressure |
|---|---|---|---|
| HVLP (low pressure, high transfer) | 18–20 sec | 2:1:0.5 (with hardener) | 2–2.5 bar |
| LVLP (low volume, low pressure) | 16–18 sec | 2:1:0.3 | 1.5–2 bar |
| Conventional (usual) | 20–22 sec | 2:1:0.8 | 3–4 bar |
| Airless spray | 22–25 sec | Minimum dilution (1:0.2) | 150–200 bar |
⚠️ Attention: When working with HVLP spray guns Never thin the paint by eye! These systems are sensitive to viscosity: too thin paint will cause smudges, and thick paint will cause shagreen. Use viscometer (costs ~500 rubles) or monitor the flow time through a funnel with a 4 mm hole (should be 18–22 seconds).
To check viscosity without instruments, you can use a simple test: dip a clean stick into the paint and lift it up. If the paint runs off uniform stream no drops or breaks - normal viscosity. If it drips, it’s too thin; if it “stretches” like a thread, it’s thick.
What happens if you dilute the paint incorrectly?
Insufficient dilution will result in shagreens (uneven surface), excess - to smudges and long drying. In both cases, you will have to sand and repaint the part. Particularly critical for metallic paints: incorrect viscosity causes leopard effect (uneven distribution of pigment), which cannot be corrected even with varnish.
Common mistakes and how to avoid them
Even experienced painters sometimes make mistakes when thinning paint. Here are the top 5 mistakes and their consequences:
- Using a different brand of solvent.
For example, dilution Sikkens solvent Mobihel. This leads to chemical incompatibility: the paint may curl, lose its shine or adhere poorly to the primer.
- Violation of hardener proportions.
An excess of hardener makes the paint brittle (it cracks on impact), while too little makes the paint soft (fingerprints remain).
- Thin the paint in advance.
Acrylic enamels with hardener must be used within 4–6 hours. If you dilute them in the evening and paint in the morning, the paint will lose its fluidity.
- Ignoring temperature.
At +5°C, a “slow” solvent will not dry out in a day, but at +35°C, a “fast” solvent will produce bubbles.
- Unfiltered paint.
Small lumps or dust clog the spray gun nozzle and spoil the texture. Always filter paint through
mesh 190–220 microns.
🔹 Secret from the masters: If you paint vertical surfaces (for example doors), add 5% to the paint anti-silicone additive (sold in auto stores). This will prevent paint from running off and forming “tears” on the lower edges of the parts.
Always test thinned paint on a sample surface (such as an old part or piece of metal). This will allow you to evaluate flow, drying speed and final color before applying to your vehicle.
How to dilute paint for airbrush and brushes
If you apply paint not with a spray gun, but brush or airbrush, dilution rules are changing. For a brush, the paint should be thicker so as not to leave lint marks. For airbrushing - thinner to pass through a needle 0.2–0.5 mm.
- 🖌️ For the brush:
- Thin the paint to consistency liquid sour cream.
- Proportion:
3 parts paint: 1 part thinner(without hardener if the paint is one-component). - Apply 2-3 thin layers with 15-20 minutes drying in between.
- 🎨 For airbrush:
- Use special solvent for airbrush (for example, Createx Airbrush Reducer).
- Proportion:
1 part paint: 1 part solvent(for details) or1:2(for large areas). - Compressor pressure:
1.5–2 bar.
⚠️ Attention: When working with an airbrush, never use fast solvents! They evaporate too quickly, clogging the needle and causing a "web" on the surface. Optimal choice - slow solvents or special compositions for airbrushing.
To check the thickness of airbrush paint, drop it onto the glass: if the drop spreads until 2–3 cm in 10 seconds - the consistency is correct. If it spreads faster, add paint; if it spreads slower, add solvent.
FAQ: Frequently asked questions about car paint thinning
Is it possible to thin car paint with white spirit?
White spirit is suitable only for alkyd enamels (for example, Duxone). It is not suitable for acrylic paints - it destroys the binder. For modern car enamels, use specialized solvents based on butyl acetate or xylene.
How to dilute paint if there is no proprietary solvent?
As a last resort, for acrylic paints you can use solvent R-12 (for average conditions) or R-5 (for hot weather). Suitable for base paints R-7. But remember: this is a temporary solution - the quality of the coating will be worse than with a branded thinner.
How to thin dried car paint?
If the paint has thickened but not become a hard lump, try adding 5–10% solvent and leave for 12 hours. This will not work for acrylic enamels with a hardener - they can only be thinned in the first 4-6 hours after mixing. It is better to throw away dried paint.
Is it possible to mix paints from different manufacturers?
Mix paints from different brands not recommended, since they may have different chemical bases. An exception is if both manufacturers are part of the same concern (for example, PPG and Nexa Autocolor). Always do a test mix on a small volume.
How to dilute paint for painting plastic parts?
For plastic (bumpers, spoilers) use solvent with plasticizer (for example, PPG D8115 or Sikkens Autoclear Plastic). Proportion: 2 parts paint: 1 part solvent: 0.5 parts plasticizer. This will prevent the coating from cracking.