Which nozzle to apply metallic base: size, pressure and technique for flawless coverage

Application metallic bases - one of the most important stages of car painting, where even little things determine the final result. Incorrectly selected nozzle (spray gun nozzle) may cause uneven spraying, excessive consumption of material or defects like fisheye and stripes. At the same time, there is no universal answer to the question “what is the ideal nozzle size?” does not exist: the choice depends on base viscosity, metallic type, air pressure and even weather conditions in the workshop.

Many novice craftsmen mistakenly believe that the wider the nozzle, the easier it is to apply paint. In practice nozzle too large leads to rough texture and drips, and excessively fine - to insufficient coverage and increased layers. In this article we will analyze exact parameters for different scenarios: from thin "dusty" metallics up to thick bases with large aluminum chips, and also reveal professional tricks for setting up equipment.

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Why nozzle size is critical for metallics

The metallic base is suspension of pigments and metal particles in a solvent, where the key role is played even distribution of crumbs on the surface. If the nozzle is too narrow, particles aluminum or mica will not pass through the nozzle and will settle at the bottom of the tank, which will lead to dull shade or stains. A nozzle that is too wide, on the contrary, creates excess paint cloudwhere metal flakes lie chaotically - as a result, the coating loses color depth and "play" in the light.

Additional complexity - base viscosity. Manufacturers (eg PPG, Sikkens, Mobihel) indicate the recommended viscosity in seconds by viscometer (usually 18–22 sec at 20°C). The thicker the base, the wider the nozzle should be. For example, for thin "dusty" metallics (type Silver Metallic) enough nozzle 1.2–1.3 mm, and for thick bases with coarse crumbs (for example, Ford Moondust Silver) will be required 1.4–1.5 mm.

• 🔍 Fine nozzle (1.0–1.2 mm): suitable for liquid bases and small parts (mirrors, handles). Risk: Particle clogging.
• ⚖️ Medium nozzle (1.3–1.4 mm): Universal choice for 80% metallics. Optimal for large panels (hood, roof).
• 🚗 Large nozzle (1.5–1.7 mm): only for thick bases with large crumbs or at high temperature in a box (+25°C and above).

⚠️ Attention: If you are using HVLP spray gun (low outlet pressure), the nozzle should be at 0.1mm widerthan for HP systems (high blood pressure). For example, for HVLP it is optimal 1.4 mm instead of 1.3 mm.

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Dependence on the type of metallic: nozzle selection table

Not all metallics are the same: some contain fine aluminum dust, others - large mica flakes, third - combined pigments. Paint manufacturers classify bases according to size of metal particles, which directly affects the choice of nozzle. Below is a table for popular types:

Metallic type	Color examples	Recommended nozzle (mm)	Pressure (bar)	Features
Thin "dusty"	Silver Metallic, Graphite Grey	1.2–1.3	2.0–2.5	Sensitive to spray distance (20–25 cm).
Medium with aluminum chips	Ford Moondust, BMW Mineral White	1.3–1.4	2.2–2.8	Requires thorough mixing before application.
Rough with mica	Toyota Super White, Nissan Brilliant Silver	1.4–1.5	2.5–3.0	Risk of "striations" - apply in a crisscross pattern.
Pearlescent (3-layer)	Honda Polished Metal, Mazda Machine Grey	1.3 (base) / 1.5 (mother of pearl)	2.0–2.5	Mother of pearl is applied as the last layer with an enlarged nozzle.

For mother-of-pearl and chameleon paints separate rules apply: the base (usually metallic) is applied with a standard nozzle, and the mother of pearl itself is applied to 0.1–0.2 mm wider. This is due to the fact that pearlescent pigments are larger and require a “softer” spray.

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Air pressure: how it affects the result

Nozzle and pressure - inseparable pair. Even a perfectly selected nozzle will fail if the air pressure does not match paint viscosity and type of equipment. General rule:

• 📉 Low pressure (1.5–2.0 bar): suitable for HVLP spray guns and liquid bases. The downside is slow application.
• ⚖️ Medium pressure (2.2–2.8 bar): Universal for most metallics. Optimal for HP and RP systems.
• 📈 High pressure (3.0+ bar): Only for thick bases or when working in hot conditions. Risk: Excessive fogging.

Key parameter - nozzle outlet pressure (not on the compressor pressure gauge!). To measure it use regulator with pressure gauge on the spray gun handle. For example, if the compressor shows 4 bar, and on the spray gun after the gearbox - 2.3 bar, you need to focus on the second value.

⚠️ Attention: When the temperature in the box is higher 25°C pressure should be reduced by 0.2–0.3 barto avoid too rapid evaporation of the solvent and the appearance of “dry fog”.

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Application technique: how to avoid defects

Even with the correct nozzle and pressure incorrect spray technique will spoil the result. Main mistakes:

1. Incorrect distance: optimal - 20–25 cm from the surface. Closer - drips, further - "dust".
2. Uneven driving speed: The hand should move at a constant speed (~30–40 cm/s).
3. Non-overlapping layers: each new pass must overlap the previous one by 50–70%.

Critical for metallics spray direction:

- First layer - horizontal movement (from left to right).

- Second layer - vertical (from top to bottom).

- Third (if necessary) - criss-cross at an angle 45°.

Check the cleanliness of the nozzle (blow with compressed air)|Adjust the outlet pressure (2.2–2.8 bar)|Install the correct nozzle (1.3–1.5 mm depending on the base)|Test the spray pattern on a sample panel|Stir the base for 5–7 minutes before pouring into the reservoir-->

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Common problems and how to avoid them

Even experienced painters encounter defects when working with metallic paints. Let's look at typical cases and solutions:

Defect	Reason	Solution
"Fisheye"	Surface contamination (silicone, wax) or too high pressure.	Clean the panel with wipe, reduce pressure on 0.3 bar.
Striping	Uneven distribution of metal particles or incorrect spray angle.	Apply crosswise, increase the distance to 25 cm.
Dull color	The nozzle is too narrow - metallic does not pass through the nozzle.	Replace the nozzle with 1.4–1.5 mm, mix the base thoroughly.
Drips	Too thick base or low hand speed.	Dilute the base by 5–10%, increase the spray speed.

Critical error: using the same nozzle for base and varnish. The varnish requires a nozzle 0.1–0.2 mm wider (for example, 1.5–1.7 mm), otherwise it will lie too “dry” and will not provide gloss.

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Professional tricks from the masters

Experienced colorists share life hacks that save time and improve results:

• 🔄 Double filtration: Before pouring into the tank, pass the base through two filters - first 190 microns, then 125 microns. This will even remove microparticles that can clog the nozzle.
• 🌡️ Temperature control: if it’s colder in the box 18°C, preheat the base until 20–22°C in warm water. This will reduce viscosity and improve spray.
• 🎨 Test panel: Before working on the machine, apply the base to aluminum or plastic panel the same color. This will help calibrate the pressure and speed.

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FAQ: Answers to frequently asked questions

Is it possible to apply metallic with a 1.7 mm nozzle?

Technically yes, but only for very thick bases (for example, Mercedes Designo) or at high temperatures in the box (+30°C and above). In other cases, this will lead to rough texture and waste of material. The optimal range for metallics is 1.2–1.5 mm.

How can you tell if the nozzle is clogged during operation?

Signs of a clogged nozzle:

• Uneven spray fan (broken lines).
• Increasing pressure on the pressure gauge with the same air flow.
• The appearance of paint spitting.

Solution: Stop immediately, flush the nozzle with solvent and blow with compressed air. If clogging recurs, check the filters on the compressor and in the spray gun.

Do I need to change the nozzle when changing the metallic color?

Not necessary if the colors are similar in viscosity (for example, both are “dusty”). However, when moving from subtle metallic on thick with mica it is better to replace the nozzle (for example, with 1.3 mm on 1.5 mm). Also be sure to wash the spray gun. universal cleaner (for example, PPG DX330) to avoid mixing of pigments.

What pressure should I set for the SATA RP spray gun?

For SATA RP (reduced pressure system) optimal settings:

• Duza: 1.3–1.4 mm (depending on the base).
• Inlet pressure: 2.5–3.0 bar.
• Outlet pressure (at handle pressure gauge): 0.7–1.0 bar.

Important: SATA RP is sensitive to air quality - use moisture-oil separator and filter 5 microns.

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