High-quality painting of a car or parts depends not only on the skills of the painter, but also on the correct preparation of the paint material. Even the most expensive paint and a professional spray gun will not save the situation if the composition is not properly diluted, filtered or applied under the wrong pressure. In this article we will look at all stages of paint preparation for working with compressor equipment - from the selection of consumables to the subtleties of setting up the atomizer.

Many beginners make a critical mistake: they think that it is enough to just pour paint into the tank and start painting. In practice incorrect viscosity leads to smudges or “orange peel”, and contamination in the composition leads to clogged nozzles and coating defects. Professionals spend up to 30% of the total painting time preparing the material, and this is justified: this approach guarantees an even layer, durability of the coating and no rework.

We won't talk about "the importance of following instructions" - instead you'll get specific numbers, dilution schemes and practical life hacks, which save time and paint. From theory to practice: let's get started.

1. Selection of paint and thinner: compatibility and working conditions

The first step is to decide on the type of paint and the appropriate thinner. There are three main types of car enamels on the market:

  • 🔴 Acrylic - the most popular for body work due to their durability and ease of use. Requires dilution acrylic thinner (for example, Sikkens Autoclear or Mobihel).
  • 🟡 Alkyd - cheaper than acrylic ones, but take longer to dry and are less resistant to UV. Diluted white spirit or specialized alkyd thinners.
  • 🔵 Metallics and pearls - require a special approach due to pigments. The thinner must be low viscosityso that metal particles do not settle (for example, PPG D8105).

The key parameter when choosing a thinner is ambient temperature. Manufacturers indicate three options on the cans:

Thinner type Application temperature Examples of brands
Fast (Fast) 15–25°C Sikkens Thinner 760, Lesonal Rapid
Average (Normal) 20–30°C PPG DX330, Mobihel Universal
Slow (Slow) 25–35°C Spies Hecker 5600, Duxone Retarder

⚠️ Attention: Using the “wrong” temperature thinner will result in uneven drying — the top layer may set faster than the bottom layer, causing cracks or clouding. For example, when painting in a garage in winter (<10°C), even a “fast” thinner will take too long to dry, and in the summer in the sun (>30°C), the “slow” thinner will not have time to spread, leaving shagreen.

Professionals recommend having in stock universal thinner (for example, Lesonal Universal 530-535), which is suitable for most acrylic paints at temperatures of 18–25°C. But for an ideal result, it is better to use a thinner of the same brand as the paint - this guarantees chemical compatibility.

📊 What type of paint do you use most often?
Acrylic
Alkyd
Metallic/pearl
Other

2. Equipment: what kind of spray gun and compressor is needed

Not only the quality of spraying, but also paint preparation requirements. Let's look at the key parameters:

  • 🔧 Spray gun:
    • Suitable for basic work HVLP (High Volume Low Pressure) with nozzle 1.3–1.4 mm for acrylic and 1.5–1.7 mm for soil.
    • Professional models (eg. SATAjet 5000 or Iwata W-400) allow you to adjust the shape of the torch and the air supply, which reduces paint consumption.
  • 💨 Compressor:
    • Minimum Requirements: Performance 250–300 l/min and receiver 50 l.
    • For continuous operation you need oil compressor (for example, Fubag VOF 300/50) - it heats up less and lasts longer.

⚠️ Attention: If the compressor produces air with oil vapor (typical for cheap oil-free models), the paint will peel off after 1-2 years. Be sure to use moisture-oil separator (for example, Condor MAF-50) and fine filter (5 µm) at the entrance to the spray gun.

Before starting work, check the pressure on the compressor pressure gauge and adjust it according to the recommendations of the spray gun manufacturer. For example, for HVLP-pistols working pressure at the inlet - 2.0–2.5 bar, and at the outlet (at the nozzle) - 0.7–1.0 bar. Use gearbox with pressure gauge for fine tuning.

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If the spray gun is new, wash it before painting for the first time. solvent (for example, P646) - this will remove factory grease and dust particles from the channels.

3. Paint thinning: proportions and viscosity control

The most common mistake made by beginners is to thin the paint by eye. Professionals use viscometer (for example, DIN-4 or Ford Cup #4) for accurate viscosity measurement. Optimal values:

  • 🎨 Acrylic paint: 18–22 sec at 20°C (according to DIN-4).
  • 🔘 Ground: 20–25 sec.
  • ✨ Varnish: 16–20 sec.

Typical dilution ratios (paint : thinner : hardener for 2K systems):

Material type Proportion Example (per 1 liter of paint)
Acrylic base enamel 2 : 1 : 0.5 1000 ml paint + 500 ml thinner + 250 ml hardener
Acrylic varnish 2 : 1 : 0.5 1000 ml varnish + 500 ml thinner + 250 ml hardener
Soil filler 4 : 1 : 0.5 1000 ml primer + 250 ml thinner + 125 ml hardener

🔹 How to dilute correctly:

  1. Add to paint hardener (if required) and stir with a wooden stick 2–3 minutes.
  2. Gradually pour in the diluent, monitoring the viscosity with a viscometer.
  3. After reaching the desired viscosity, give the mixture stand for 10–15 minutes - this will allow air bubbles to escape.

⚠️ Attention: If you dilute the paint too much, it will drain from vertical surfaces, and if not enough, “shagreen” is formed. For example, with viscosity 15 sec (too liquid) smudges will appear on the vertical panels, and when 25 sec (too thick) the paint will not flow evenly.

☑️ Preparing paint for dilution

Done: 0 / 5

4. Paint filtration: why is it critical?

Even a new can of paint may contain microparticles of dust, lumps of pigment or dried drops. If they are not removed, they the spray gun nozzle will clog (especially with a diameter 1.3 mm) or will remain on the painted surface as defects. Filtration is carried out in two stages:

  1. Coarse filtration: The paint is filtered through nylon filter with cell 190–250 µm (for example, 3M Paint Strainer). This removes large particles and clumps.
  2. Fine filtration: Before pouring into the spray gun tank, the material is passed through paper filter 100–120 µm (for example, SATA Filter 100).

🔹 How to filter correctly:

  • 🕳️ Pour paint into clean plastic funnel with filter.
  • 🧴 Do not press the filter or speed up the process - this may tear the material.
  • 🗑️ After filtration, check the filter against the light: if it is clogged, repeat the process with a new one.

⚠️ Attention: Never use household sieves or gauze - their pores are too large (500+ microns), and they will not retain minor contaminants. Also avoid metal mesh filters, as they can oxidize and add rust particles to the paint.

Professionals use closed filtration systems (for example, DeVilbiss Paint Cup System), which prevent dust from getting into the paint during operation. This is especially true when painting in dusty rooms or outdoors.

What happens if you don't filter the paint?

Unfiltered particles will clog the spray gun nozzle (you will have to disassemble and clean it), and “flies” will remain on the painted surface - small tubercles that will have to be sanded and repainted. In the worst case, the defect will appear only after varnishing, and the work will have to be completely redone.

5. Setting up the spray gun and test spraying

After preparing the paint, you need to set up the spray gun. Main parameters:

  • 🎯 Inlet pressure: 2.0–2.5 bar (regulated by the gearbox on the compressor).
  • 🔄 Outlet pressure (at nozzle): 0.7–1.2 bar (depending on the type of gun).
  • 📐 Torch Shape: Suitable for most jobs oval torch with width 250–300 mm.
  • 💧 Paint supply: Adjustable with a screw on the gun - start from the middle position.

🔹 Test Spray:

  1. Pour the prepared paint into the tank and make test pass on cardboard or an old part.
  2. Evaluate the shape of the torch: it should be uniform, without "tails" around the edges.
  3. Check paint consumption: If dry spots remain on the surface, increase the feed.

⚠️ Attention: If during test spraying the paint "spits" (large drops are formed), this is a sign:

  • Dirty nozzle (needs to be cleaned) solvent and blow with compressed air).
  • Viscosity too high (add 5-10% thinner and stir).
  • Incorrect pressure (check pressure gauge and adjust reducer).

Professionals use test cards (for example, SATA Test Panel) to assess the quality of spraying. There are marks on the card that help control the uniformity of the layer and the absence of defects.

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Ideal spraying is when the paint goes “wet on wet” without smudges or dry spots. If the first layer looks matte, this is normal - the gloss will appear after varnishing.

6. Common mistakes and how to avoid them

Even experienced painters sometimes make mistakes when preparing paint. Here are the most common:

Error Consequences How to fix
Incompatible thinner Paint curls or does not dry Use thinner of the same brand as the paint.
Unfiltered paint "Flies" on the surface, clogged nozzle Double filtration: 190 µm + 100 µm
Incorrect viscosity Smudges or "shagreen" Monitor with a viscometer (18–22 sec for acrylic)
Dirty spray gun Uneven spray, droplets Rinse solvent after each use

🔹 Tips from the professionals:

  • 🌡️ If the room temperature is lower 15°C, use infrared heater - this will speed up drying and prevent clouding of the varnish.
  • 🌀 When painting metallics stir the paint every 10 minutesso that the pigments do not settle to the bottom.
  • 🛢️ Don’t store diluted paint anymore 24 hours - the hardener will begin to polymerize and the material will become unusable.

⚠️ Attention: If you are working with water-soluble paints (for example, PPG Envirobase), remember what they require special water-based thinners and anti-silicone additives (for example, Sikkens Balancer). The use of conventional solvents will lead to paint delamination.

7. Care of equipment after painting

Proper care of the spray gun and compressor extends their service life and guarantees consistent painting quality. Basic steps:

  1. Cleaning the spray gun:
    • Immediately after work, rinse the tank and nozzle solvent (for example, P646 for acrylic or white spirit for alkyd paints).
    • Disassemble the gun and clean the needle, nozzle and air passages soft brush.
    • Blow with compressed air (pressure 2–3 bar).
  • Compressor maintenance:
    • Drain the condensate from the receiver through bleed valve.
    • Check the oil level (for oil models) and add if necessary.
    • Replace filters (moisture oil separator and carbon) every 500 hours of operation.

    🔹 What not to do:

    • 🚫 Leave paint in the spray gun tank for more than 1 hour - it will dry out and clog the channels.
    • 🚫Use metal objects to clean the nozzle - this scratches the surface and disrupts the shape of the torch.
    • 🚫 Store the spray gun in a dusty place without a cover - dust will get into the air channels.

    Professionals recommend leading service log, where the dates of cleaning, filter replacement and repairs are recorded. This helps monitor the condition of equipment and prevent breakdowns.

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    Regular cleaning of the spray gun after each use saves up to 30% of paint due to stable atomization and prevents expensive equipment repairs.

    FAQ: Frequently asked questions about paint preparation

    Is it possible to dilute paint with gasoline or kerosene?

    No, this will lead to paint delamination and loss of adhesion. Gasoline and kerosene contain impurities that react with enamel components. For dilution, use only special thinners (for example, Lesonal or PPG).

    How can you tell if the paint is too thick?

    Signs of excessive viscosity:

    • The paint lays down in “bumps” (shagreen).
    • The spray pattern is uneven, with “tails”.
    • Streaks from the movement of the gun are visible on vertical surfaces.

    Solution: add thinner in small portions (5-10%) and check the viscosity with a viscometer.

    What to do if the paint in the tank begins to thicken?

    If the paint costs more in the tank 30 minutes, it begins to dry out. Don't try to dilute it directly in the tank. - this will lead to lumps. Drain off the residue, rinse the tank with solvent and prepare a new batch of paint.

    Can I use the same thinner for primer and paint?

    No, primers and enamels have different chemical compositions. For soils use special thinners (for example, PPG DP40), which provide better adhesion. Paint thinner can make the primer too thin, reducing its filling properties.

    How to store thinned paint if work is interrupted?

    Thinned paint can be stored no more than 24 hours in hermetically sealed container (for example, in a jar with a lid, wrapped in cling film). Place the container in a cool place (15–20°C) and exclude light. Stir thoroughly before use.