Painting a car with a spray gun is a process where the quality of the result depends 70% on the correct preparation of the paint and varnish material. Even a professional spray gun SATAjet 5000 or WALCOM CW-100 will not save the situation if the paint is diluted in violation of the technology: too thick will lead to “orange peel”, liquid - to drips and low coverage. And errors with the solvent can cause peeling of layers a month after the repair.
Many self-taught masters believe that it is enough to “dilute it to the state of milk” - but this is a grave mistake. Modern car enamels (especially base paints with chameleon effect or metallic) require strict adherence viscosity, temperature and even air humidity. For example, for acrylic enamels type Mobihel or Vika It is critical to use the “native” solvent from the manufacturer, otherwise the pigments may separate in the gun tank.
In this article - step by step instructions with tables of proportions for different types of paints, secrets of professionals in filtration and viscosity testing, as well as an analysis of typical mistakes that spoil the result even with expensive equipment.
1. What kind of paint can be thinned for a spray gun?
Not all paint materials are suitable for spraying through a paint gun. Here main types of car enamels, which are diluted for the spray gun:
- 🔴 Acrylic enamels (one-component and two-component): most popular for local repairs. Examples: Mobihel Acryl-2K, Vika 2K HS.
- 🟡 Basic paints (for “base + varnish” systems): used for metallics, pearls. Popular: Sikkens Autowave, PPG Deltabase.
- 🟢 Alkyd enamels: cheaper than acrylic ones, but take longer to dry. Example: Duxone Alkyd.
- 🔵 Water-soluble paints: environmentally friendly option, but require special solvents. Brands: Standox Aquabase, Spies Hecker Permahyd.
❌ Do not dilute for spray gun:
- 🚫 Nitro paints - are too toxic and require special equipment.
- 🚫 Powder paints — applied electrostatically, not by spraying.
- 🚫 Spray paints - are ready for use, dilution will disrupt the pressure.
For metallics and pearls critical to use special thinners for base paints (for example, PPG DT870 or Sikkens Autoclear LV). Regular solvent 646 destroys the pigments, and the “chameleon” effect will disappear.
2. What you need to thin the paint
Before thinning the paint, prepare your tools and materials. Without them it is impossible to achieve the correct consistency:
- 📏 Viscosity gauge (viscometer) - for accurate viscosity measurement. Popular models: DIN-4 or ISO-2431.
- 🧪 Measuring containers — plastic cups with divisions (volume 100–500 ml).
- 🔄 Solvent - must match the type of paint (for example, P812-60 for acrylic or DT870 for the base).
- 🧴 Hardener - for two-component systems (for example, Vika Hardener).
- 🧻 Paint filter - mesh (190 microns) or paper (for final filtration).
- 🌡️ Thermometer - the temperature of the paint and solvent should be 20–25°C (for other values the viscosity changes!).
⚠️ Attention: Never use solvent R-646 for base paints with effect metallic or pearl! It is aggressive on aluminum pigments, and the paint will lose its shine after 2-3 months.
For water-soluble paints additionally required distilled water and a special diluent (for example, Standox Aqua Plus). Regular tap water contains salts that can corrode the metal underneath the paint.
☑️ Preparing for paint thinning
3. Dilution proportions: table for different paints
The ratio of paint, solvent and hardener depends on:
- 🔹 Type of paint (acrylic, base, alkyd).
- 🔹 Temperatures in the paint booth.
- 🔹 Brands of equipment (pressure at the outlet of the pulverizer nozzle).
Below - basic proportions for standard conditions (temperature +20°C, humidity 50–70%):
| Paint type | Paint | Solvent | Hardener | Viscosity (DIN-4) |
|---|---|---|---|---|
| Acrylic 2K (HS) | 100% | 50–60% | 50% (of paint volume) | 18–22 sec |
| Base paint (metallic) | 100% | 30–50% | — | 14–16 sec |
| Alkyd enamel | 100% | 40–50% | — | 20–24 sec |
| Water soluble | 100% | 10–20% (water + thinner) | 20–30% | 15–18 sec |
⚠️ Critical nuances:
- For hot drying (temperature +60°C) the amount of solvent is reduced by 10–15%.
- When painting vertical surfaces (for example, doors), the paint is made 5–10% thicker to avoid drips.
- For HVLP spray guns (for example, Iwata W-400) the viscosity should be 2-3 seconds lower than for conventional guns.
If you paint plastic parts (bumper, mirrors), add 5–10% to paint plasticizer (for example, PPG Flex Additive). This will prevent cracking due to temperature changes.
4. Step-by-step instructions: how to thin the paint
Follow this algorithm to avoid errors:
- Step 1. Preparing the paint.
Stir the paint in the jar with a wooden stick for 3-5 minutes. If there is a film on the surface, remove it no shaking (film may contain hardened particles).
- Step 2. Add solvent.
Measure out the required amount of paint and thinner using a measuring cup. Pour solvent first, then paint - this makes it easier to control the consistency.
- Step 3. Mixing.
Use stirrer at low speed (400-600 rpm) for 5-7 minutes. Do not allow bubbles to form!
- Step 4. Viscosity check.
Pour the finished mixture into the viscometer DIN-4 and note the expiration time. If the viscosity does not correspond to the table, add solvent (to decrease) or paint (to increase).
- Step 5. Filtration.
Filter the paint through mesh filter 190 microns, then through paper filter (for example, 3M Paint Filter). This will even remove microparticles that can clog the nozzle.
- Step 6: Test spray.
Apply paint to test surface (for example, an old hood). Evaluate the texture: if there is a “sand effect”, the paint is too thick; if there are drips, the paint is too thin.
⚠️ Attention: If you dilute chameleon effect paint (for example, House of Kolor Kameleon), never use metal stirrers! Pigments are sensitive to metal - use only plastic or wooden sticks.
What happens if you don't filter the paint?
Unfiltered particles clog the nozzle of the spray gun, which leads to uneven spraying (“spitting” of paint). In addition, debris may remain on the painted surface, and after drying it will have to be sanded and repainted.
5. Common mistakes and how to avoid them
Even experienced painters sometimes make mistakes when thinning paint. Here TOP-5 misses and their consequences:
- 🔴 Using the wrong solvent.
For example, solvent R-12 for alkyd enamels in acrylic paint will cause dullness and poor adhesion. Always check the manufacturer's recommendations on the can!
- 🟡 Failure to comply with temperature conditions.
If the paint is colder than +15°C, it will be thicker and you will add excess solvent. At +30°C, on the contrary, the paint will become too liquid.
- 🟢 Poor mixing.
Insufficient mixing leads to separation of pigments (especially in metallics). As a result, spots of different shades will appear on the car.
- 🔵 Ignoring test spray.
Without a test on the rough surface you may miss uneven spray or incorrect invoice.
- ⚪ Saving on filters.
Cheap filters allow microparticles to pass through, which will clog the nozzle HVLP gun in 10 minutes of work.
💡 Life hack from professionals: If you paint metallic and are afraid of pigment separation, add 1–2% to the paint anti-silicone additive (for example, Sikkens Balancer). This stabilizes the pigments in the solvent.
Main rule: always follow the paint manufacturer's instructions, even if the “old-fashioned methods” seem simpler. Modern car enamels are sensitive to little things!
6. How to check viscosity without a viscometer
If you don't have it at hand DIN-4, you can approximately estimate the viscosity using “old-fashioned” methods:
- 🥄 Stick method.
Dip a wooden stick into the paint and lift it up. If the paint runs off at a speed of 1 drop per second — viscosity is close to normal. If the drops fall more often, the paint is liquid; less often, the paint is thick.
- 🧃 Glass method.
Pour paint into a plastic cup and tilt it at a 45° angle. If the paint runs out in a thin stream — viscosity is normal. If it flows in a stream, it is too liquid.
- ✋ Hand method.
Dip your finger into the paint and remove. The optimal consistency is when the paint envelops the finger, but does not drip when the hand is held horizontally.
⚠️ Important: These methods only provide a rough estimate! For professional painting a viscometer is required, especially when working with base paints or mother-of-pearl.
If you paint matte enamel (for example, Mobihel Matt), the viscosity should be 2–3 seconds higher than for glossy paints. Matte finishes are more sensitive to smudges.
7. Features of dilution for different spray guns
The type of paint gun directly affects the required paint viscosity. Here are the key differences:
| Gun type | Recommended viscosity (DIN-4) | Inlet pressure (bar) | Features |
|---|---|---|---|
| HVLP (eg. SATAjet 5000) | 14–18 sec | 2.0–2.5 | Requires thinner paint due to low outlet pressure. |
| LVLP (eg. WALCOM CW-100) | 16–20 sec | 1.5–2.0 | Universal for most paints, less fog. |
| Conventional (for example, DeVilbiss GTI) | 18–22 sec | 2.5–3.5 | Suitable for thick paints, but more overuse. |
| Mini-HVLP (for parts) | 12–15 sec | 1.0–1.5 | Used for painting mirrors or handles. |
For HVLP guns It is critical to maintain viscosity: if the paint is too thick, the gun will “spit” rather than spray. For conventional For pulverizers, a slight deviation in the direction of density can be allowed.
💡 Advice: If you are using adjustable nozzle gun (for example, Iwata Supernova), for thick paints (for example, primer), install a nozzle 1.7–2.0 mm, for liquid (varnish) - 1.3–1.4 mm.
8. FAQ: Frequently asked questions about paint thinning
Is it possible to thin paint with water instead of thinner?
❌ Not if it's not water soluble paint. For regular acrylic or alkyd enamels, water will cause coagulation paints and formation of lumps. For water-soluble systems, water is used, but mixed with a special diluent (for example, Standox Aqua Plus).
How long can diluted paint be stored?
⏳ Divorced two-component paint (with hardener) must be used within 4–6 hours. One-component acrylic enamels can be stored in an airtight container for up to 24 hours, but they need to be filtered again before use.
Why did streaks appear after painting?
🎨 Leaks occur due to:
- Too liquid paint (viscosity below 12 sec according to DIN-4).
- High humidity in the painting booth (more than 70%).
- Low air pressure in the gun (less than 1.5 bar).
- Too close range to the surface (optimally 15–20 cm).
🔧 How to fix: If the streaks are small, wait until dry and polish the surface with paste. 3M Perfect-it. For heavy leaks - sanding P1200–P1500 and repainting.
Is it possible to mix paints from different manufacturers?
⚠️ Risky! Even if both paints are acrylic, they may have different chemical bases. For example, mixing Mobihel and Vika sometimes leads to delominations (delamination) after 1–2 years. If you have to mix, do a compatibility test: mix a small amount and apply to a metal plate. If wrinkles do not appear after a day, you can use it.
How to thin paint for painting in a cold garage?
❄️ At temperatures below +15°C:
- Use "winter" solvent (for example, PPG DT885).
- Reduce the amount of solvent by 10–15% (the paint will already be thicker due to the cold).
- Warm the paint and solvent until 20–25°C before mixing (for example, in warm water).
- Increase gun inlet pressure by 0.3–0.5 bar.
⚠️ Do not use common solvent 646 in the cold - it evaporates too quickly, and the paint will appear “dry” (without gloss).