Which nozzle to apply varnish to a car: size, type of spray gun and nuances of work

The quality of car varnishing depends 70% on the correct choice of equipment. Even professional varnish Sikkens or PPG will lie unevenly if you use the wrong nozzle (nozzle) of the spray gun. And mistakes here are costly: from excess material consumption up to irreversible "orange peel", which will have to be sanded and polished for hours.

Beginners often think that “the wider the nozzle, the faster the work.” This is a dangerous misconception. A nozzle that is too large will give a rough textured layer, while a small nozzle will lead to overheating of the varnish and bubbles. In this article we will look at how to choose the nozzle diameter for the type of varnish, the viscosity of the material and even the weather in the workshop. And also why professionals sometimes use two nozzles for one layer.

Spoiler: there is no universal size. Even for standard acrylic varnish 2K the optimal diameter varies from 1.3 mm up to 1.7 mm depending on conditions. And that's not to mention HS-varnishes or ceramic coatings, where the rules are different.

1. Nozzle diameter: what do the numbers 1.2, 1.4, 1.8 mm mean?

The nozzle size indicates hole diameter, through which the varnish passes. The higher the number, the thicker the jet and the higher the material consumption. But that doesn't mean that 1.8 mm always better 1.3 mm. Here's how size affects the result:

• 🔹 1.0–1.2 mm: For liquid varnishes (for example, 1K or diluted HS). It gives a thin layer with a minimal textured pattern, but requires ideal surface preparation - the slightest scratches will be visible.
• 🔹 1.3–1.4 mm: Gold standard for the majority acrylic 2K varnishes (viscosity 18–22 sec according to DIN4). Balance between application speed and quality.
• 🔹 1.5–1.7 mm: For thick varnishes (for example, PPG D8115) or working in a hot workshop. Allows you to apply thick “wet” layers, but increases the risk of smudges.
• 🔹 1.8 mm or more: Used for soils or base enamels, but not for varnish - will give a rough texture that will take a long time to polish.

A critical mistake for beginners: choosing a nozzle based on the "the more the better". In practice 1.7 mm on liquid varnish will lead to "spider web" effect (microcracks during drying), and 1.2 mm on thick material - to overheating of the gun and bubbles.

Professionals often keep on hand two spray guns with nozzles 1.3 mm and 1.5 mm: first for first layer (thin, “dusty”), the second - for finishing ("wet").

2. Spray gun type: HVLP vs RP vs LVLP

Nozzle diameter is only half the battle. The second key factor is sprayer type. It determines how much varnish gets on the car, and how much escapes into the air (and into your lungs).

Spray gun type	Material transfer (%)	Inlet pressure (bar)	Better for...	Cons
HVLP	65–75%	2.0–2.5	Beginners, small parts, eco-friendly workshops	Applies more slowly, requires a compressor with a receiver
RP	55–65%	1.5–2.0	Universal works, varnishing of large panels	More fog, needs a good exhaust
LVLP	70–80%	0.7–1.2	Professionals working with expensive varnishes	Expensive models, sensitive to material viscosity

Optimal for varnish HVLP or LVLP - they give less fog and more accurately control the layer. RP suitable for primers, but with varnish it often gives "dry" spray (small particles that do not spread).

⚠️ Attention: If your compressor produces less 250 l/min, HVLP will “spit” varnish. In this case it is better to take RP with nozzle 1.4 mm and work at reduced pressure (1.8–2.0 bar).

3. Viscosity of varnish: how does it affect the choice of nozzle

Viscosity is measured in seconds according to DIN4 (time of varnish flowing out of a funnel with a 4 mm hole). Manufacturers always indicate the recommended viscosity on the can. For example:

• 🔬 Sikkens Autoclear LV: 18–20 sec → nozzle 1.3–1.4 mm
• 🔬 PPG D8115: 22–24 sec → nozzle 1.5–1.6 mm
• 🔬 Mobihel Topcoat: 16–18 sec → nozzle 1.2–1.3 mm

If the varnish is too thick, thin it out special solvent (not acetone!). The formula is simple:

Solvent volume (ml) = (Actual viscosity − Target viscosity) × 10

Example: your varnish is leaking 28 sec, but it is necessary 20 sec. Add (28−20)×10 = 80 ml solvent on 1 l varnish

⚠️ Attention: Thinned varnish changes drying time! If >10% solvent has been added, increase the dwell time by 30-50%. Otherwise you risk getting swelling during polymerization.

4. Weather in the workshop: why different nozzles are needed in winter and summer

Temperature and humidity directly affect spreadability of varnish. Professionals regulate not only the nozzle, but also the pressure:

• ☀️ Heat (>25°C) or low humidity (<40%):
• 🔥 The varnish dries too quickly → use a nozzle 0.1 mm less (for example, 1.4 mm instead of 1.5 mm).
• 🔥 Increase the distance to the part to 25–30 cm (usually 20–25 cm).
• 🔥 Add drying retarder (up to 5% of the varnish volume).
• ❄️ Cold (<15°C) or high humidity (>70%):
• ❄️ The varnish goes on “wet” and takes a long time to dry → take the dosage 0.1 mm more.
• ❄️ Reduce the distance to 15–20 cm for better droplet merging.
• ❄️ Use fast solvent (for example, Sikkens Thinner 208).

Ignoring the climate in the workshop is the main reason "matte" varnish (underpolymerization) or smudges (excessive turnover). If your workshop is not climate controlled, keep it on hand. two nozzles with a difference of 0.2 mm.

What happens if you apply varnish at temperatures below 10°C?

The varnish will appear cloudy, with poor adhesion, and after 1–2 years it will begin to peel off in layers. Even if it looks normal visually after polishing, the microstructure of the coating will be damaged.

5. Mistakes when choosing a nozzle: what even professionals spoil

Experienced painters sometimes make mistakes - especially when changing materials or spray guns. Here are the top 5 mistakes and their consequences:

1. Using a primer nozzle for varnish (for example, 1.8 mm). Result: "shagreen" (rough texture) that even polishing cannot remove 3000 grit.
2. Working with a clogged nozzle. Signs: the varnish is coming out in spots, the gun is spitting. Solution: clean ultrasonic bath or special brush (not with a needle!).
3. Nozzle and needle mismatch. If you installed a nozzle 1.4 mm, and the needle is from 1.2 mm, the varnish will flow unevenly. Check the completeness!
4. Excessive pressure. For HVLP enough 2.0–2.5 bar. Exceeding results in “dry” spraying and overconsumption of up to 30%.
5. Ignoring the shape of the torch. Optimal for varnish oval torch (not round!). Adjust gun air caps.

⚠️ Attention: If after varnishing there are microbubbles (like tubercles), it is not the nozzle that is to blame, but polluted air. Check dehumidifier and oil filter compressor - even a drop of oil in the air will ruin the layer.

6. Professional life hacks: how to apply nail polish perfectly

Experienced painters use tricks that are not written about in the instructions. Here are some tricks for mirror shine:

• 🎨 "Double Pass": Apply the first layer with a nozzle 1.3 mm at a distance 30 cm (thin “dusty” layer), the second - nozzle 1.5 mm on 20 cm ("wet" layer). This eliminates the risk of smudges and improves adhesion.
• 🌀 Spiral movement: Do not zigzag the gun - move in a spiral from the center of the part out to the edges. This way the varnish applies more evenly.
• ⏱ Time control: The optimal gun speed is 30–40 cm/sec. Slower - smudges, faster - "dry" spraying.
• 🔍 Cardboard test: Before work, spray varnish on a piece of cardboard. An ideal torch should have smooth edges without “tails”.

For metallics and mother of pearl use a nozzle 1.2–1.3 mm and apply varnish in 2.5 layers (the first is thin, the second is normal, the third is only for problem areas). This will prevent "spotting" effective coating.

If you work with matte varnish (for example, PPG Matte Clear), take the nozzle 1.5–1.6 mm and apply one layer — multi-layer application will kill the matte effect.

7. How to clean a nozzle: why a needle and a toothpick are the worst tools

Dried varnish in the nozzle is problem #1 after work. Do not pick the hole under any circumstances. needle or toothpick - this deforms the edge of the nozzle and disrupts the shape of the torch. Correct algorithm:

1. Clean the gun immediately after use solvent (for example, Sikkens Thinner 200).
2. Remove the nozzle and soak it in ultrasonic bath with cleaning solution (5–10 minutes).
3. Clean out soft brush (for example, Sata Jet Cleaner).
4. Blow with compressed air (pressure no more than 3 bar).
5. Check the clearance with light: if scratches are visible, it is better to replace the nozzle.

For emergency cleaning (if the varnish has already dried) use special sets (for example, DeVilbiss Cleaning Kit). They include pipe cleaners of different diameters and wooden sticks that do not scratch metal.

⚠️ Attention: If after cleaning the torch becomes asymmetrical, check air cap - the side holes may be clogged. They are being cleaned toothpick, soaked in solvent.

FAQ: Frequently asked questions about varnish nozzles

Is it possible to apply varnish with a 2.0 mm nozzle to speed up the work?

No. Duza 2.0 mm Designed for primers or liquid putty. For varnish, it will give a rough texture (“orange peel”) that even polishing will not remove. Maximum size for varnish - 1.7 mm, and then only for thick materials like PPG D8115.

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

Signs of a clogged nozzle:

• 🔸 Varnish is coming unevenly (sometimes thick, sometimes liquid).
• 🔸 The gun starts"spit"in large drops.
• 🔸 The torch becomes asymmetrical.
• 🔸 Pressure on the pressure gauge jumps.

Solution: Stop immediately, flush the nozzle and check the filter on the reservoir.

Which nozzle is best for chameleon effect varnish?

For chameleons and mother of pearl critical thin application, so use nozzle 1.2–1.3 mm. Apply varnish in 2.5 layers:

1. 1st layer: 50% overlap, distance 30 cm.
2. 2nd layer: 70% overlap, distance 20 cm.
3. 3rd layer: only on problem areas (for example, hood ribs).

Pressure: 2.0–2.2 bar for HVLP.

Is it possible to use one nozzle for base and varnish?

Technically possible, but not recommended. Base enamel is usually thinner than varnish, so a nozzle is suitable for it 1.2–1.3 mm, and for varnish - 1.3–1.5 mm. If you use one nozzle, you will have to juggle pressure and distance, which increases the risk of defects.

Exception: if you are working with "wet on wet" system (for example, PPG Envirobase), where the base and varnish are applied almost simultaneously, you can use a nozzle 1.3 mm for both materials.

How does the shape of the nozzle (round vs oval) affect the result?

The shape of the nozzle hole determines torch type:

• 🔵 Round nozzle: gives round torch. Suitable for small parts (mirrors, handles), but ineffective for varnishing the body - it leaves streaks.
• 🟢 Oval nozzle: forms flat torch. Ideal for large panels (hood, roof). Allows you to apply the varnish evenly with overlap 50–70%.

All professional spray guns (for example, Sata RP or Iwata W400) come with oval nozzles. Round ones are used only in mini pistols for local repairs.