The choice of the size of the spray gun duse directly affects the texture of the coating, the consumption of material and the likelihood of defects such as shaking or stains. If you took too large duze for liquid varnish, it will lie unevenly and will drain, and a small nozzle for thick soil will lead to constant clogging of the torch and work with “spitting”. A properly selected feed channel provides the necessary spraying, creating the perfect fog for the formation of a smooth film without overspending expensive auto-enamel.
In professional car painting, the standard size for applying base coatings (metallic, mother of pearl, solid) is considered to be duce 1.3 mm. It is this diameter that allows the pigment to be evenly distributed over the surface without creating an “orange peel” effect. However, the use of a universal size of 1.3 mm is not always justified: for thick acrylic soils or liquid varnishes with a high dry residue, completely different parameters of the outlet are required, which are dictated by the viscosity of the material.
Miscalculating the diameter of the duose often causes material overruns, which can reach 30% or more. Too small a nozzle causes the painter to increase pressure at the entrance to the spray gun, which increases fog and carries part of the paint to the side, without getting to the part. On the other hand, an overly wide dusa requires perfect control of the speed of movement of the hand, otherwise the formation of subtexts on vertical surfaces becomes almost inevitable even for an experienced master.
The principle of operation of the spray gun and the influence of the diameter of the dusa
The operation of the pneumatic spray gun is based on the Venturi effect, when the flow of compressed air passing through the air nozzle creates a dilution zone that tightens the material from the tank. The size of the duse, which is a replaceable nozzle in the nozzle head, strictly doses the amount of liquid supplied. The larger the diameter of the hole, the thicker the material is able to pass through it without breaking the torch, but at the same time the volume of the supplied mixture per unit time increases.
The key parameter here is not only the physical size of the hole, but also its ratio to air pressure and paint viscosity. To form a stable torch, the material's output speed must be matched to the airflow speed. If the dusa is selected incorrectly, the balance between the force of suction and the crushing of drops is disturbed, which leads to a large grain or, conversely, to a dry, dusty coating that does not have time to spread.
Modern HVLP (High Volume Low Pressure) and LVLP (Low Volume Low Pressure) systems require a more accurate diameter selection compared to outdated conventional models. In low pressure systems, it is critical that the material has optimal fluidity to pass through the calibrated duse hole, otherwise a drop in pressure inside the channel will lead to unstable spraying.
⚠️ Warning: Never try to push thick material through a small duzue by simply adding a solvent over and above normal. This will break the chemical formula of the coating, result in loss of color, adhesion and defects after drying.
Duse fabrication material also plays a role in the durability and accuracy of calibration. Brass duses wear out faster and can change the geometry of the hole when cleaning with metal brushes, whereas stainless steel products retain their factory size for years. For professional work, it is recommended to use sets with duzas from stainless-steelThey provide a stable torch throughout the life of the tool.
When buying spare duz always check the equipment: in high-quality sets, along with duz, there is a needle, as they rub against each other individually.
Table of correspondence of the size of the duza and the type of material
There are well-established standards that determine what size duse to use for specific types of automotive materials. These recommendations are developed by paint and equipment manufacturers to achieve the best result. Below is a detailed table that helps you quickly navigate the choice of tooling for spray gun.
| Type of material | Recommended Duse Size (mm) | Features of application |
|---|---|---|
| Liquid soils (primeers) | 1.2 – 1.3 | Used for thin layers, anticorrosion treatment |
| Filler soils (acrylic) | 1.6 - 1.8 (up to 2.0) | Requires a wide channel for the passage of solid particles |
| Basic enamel (metallic/pearl) | 1.3 – 1.4 | Optimal for uniform distribution of pigment |
| Basic enamel (solid color) | 1.3 – 1.5 | A slightly larger size is allowed to speed up work |
| Lacquer (2K) and liquid rubber | 1.3 – 1.5 | Depends on the viscosity: liquid varnish - 1.3, thick - 1.4-1.5 |
Using a 1.6mm dusa to apply metallic is a gross mistake that will lead to overspending paint and strips. A large hole supplies too much material, and the master does not have time to evenly distribute it, because of which aluminum powder or mica are stacked unevenly, creating visible multi-toned areas. Conversely, attempting to apply two-component acrylic soil through a duo of 1.3 mm will require strong dilution, which will reduce the layer thickness and protective properties of the coating.
For liquid rubber (Plasti Dip) and protective coatings of the type "liquid glass" often recommended dimensions of 1.4-1.5 mm, as these materials can be more viscous. However, modern formulations are becoming more technologically advanced, so you should always read the technical card (TDS) on the product jar. The manufacturer there always indicates the recommended nozzle diameter, and this rule is a priority over the general tables.
The effect of paint viscosity on the choice of nozzle
Viscosity is the main physical parameter that determines the choice of the diameter of the duse. It is usually measured in seconds by viscometer (DIN-cup or Ford cup). The higher the viscosity index, the more difficult it is for the material to flow through a narrow hole under the action of dilution. If the viscosity of the paint is high, and the dusa is small, the torch becomes "spitting", the coating is laid with a shaking, and the master is forced to make many passes, increasing the working time.
Adjustment of viscosity is carried out by adding a solvent, but it is important to maintain a balance here. Excessive liquefaction allows for the use of a smaller duzyu, but leads to less dry residue remaining on the surface. As a result, more layers have to be applied to get the desired film thickness, which increases labor costs and the risk of defects. Therefore, it is better to choose duzyu for the standard working viscosity of the material.
The ambient temperature also affects the viscosity and therefore the choice of tooling. In a cold room, the paint becomes thicker, and for quality work, it may be necessary to dusa 0.1 mm more than standard or preheating of the material. Ignoring the temperature factor when choosing a duo often leads to the fact that the torch “breaks” in the middle of the work.
⚠️ Note: When working with two-component materials (soil, varnish), remember about the life of the mixture. If you have diluted a full jar on a thick duzu, but did not have time to develop the material in 30-40 minutes, it will begin to thicken in the tank, and even a wide duuse will stop passing it evenly.
To measure the viscosity, professionals use a viscometer, lowering it in a stirred paint and detecting the time of the jet leaking out. The seconds are checked against the table on the bank. If the leakage time is significantly higher than normal, the material is too thick for the current dusa. In such a situation, it is better to replace the nozzle with more than pouring excess “chemistry” into expensive auto enamel.
How to quickly check viscosity without a viscometer
Lower a clean wooden stick into the paint and lift it. If the paint flows down in a thin stream and breaks off sharply - the viscosity is normal. If it drips in large drops, it is too liquid. If it is stretched with a thick thread, it is too thick.
Specificity of applying different types of coatings
Applying the base enamel (base) requires maximum accuracy in the selection of dusa, as this layer is responsible for color and visual effects. For metallic and pearl, the “gold standard” is the dusa of 1.3 mm. It creates a cloud of fine mist, allowing the metal particles to fit smoothly. The use of a dusa of 1.4 mm is permissible, but requires a higher skill painter to control the spread.
Filler soils, by contrast, contain solid particles that should fill the risks from grinding. Here you need a dusa from 1.6 to 1.8 mm, and sometimes 2.0 mm for particularly thick compositions. Trying to save time and apply a thin duse of 1.3 mm will cause the hard fractions to get stuck in the filter or the nozzle itself, interrupting work every few minutes.
Lacquering is the finishing stage, where shine and smoothness are important. For most modern varnishes (MS, HS, UHS) is suitable dusa 1.3-1.4 mm. High dry residue (UHS) polishes can be quite thick, and for them manufacturers often recommend 1.4mm to ensure good spreading without having to make the coating too liquid.
- 🎨 Metallic: Require a stable, small torch (1.3 mm) to avoid the stripes.
- 🛡️ Grounds: They need a wide channel (1.7-1.8 mm) for the passage of fillers.
- ✨ Lucky: Optimal 1.3-1.4 mm for creating a glossy layer.
- 🚗 Liquid rubber: It often requires 1.4-1.5 mm due to its specific sluggishness.
Separately, it is worth mentioning local repairs, where mini-duses (0.8 mm) are used. They allow you to save material when painting small elements, but require a very liquid material and high pressure, which does not always give a high-quality result on large planes.
There is no universal dusa for all occasions. The presence of replacement heads 1.3 mm and 1.7 mm in the arsenal will cover 95% of tasks in body repair.
Frequent errors in selection and operation
One of the most common mistakes is to ignore the state of the filters when changing the size of the duose. The transition from the ground to the base requires not only a change of the nozzle, but also a thorough washing of all channels, needle and air cap. The remaining particles of soil in the spray gun when working through a thin duse of 1.3 mm will instantly cause a clog and spoil the coating on the car body.
Also, masters often forget to adjust the supply of material (screw on the back of the spray gun) when changing the duo. Having installed a wide duse of 1.8 mm, it is necessary to reduce the stroke of the needle so as not to fill the detail. Conversely, for a thin dusa of 1.2 mm, the feed must be opened as much as possible, otherwise the torch will be dry. The setting is made by test spraying on the test card.
Improper cleaning of the dusa with metal objects (needles, wire) leads to scratches inside the calibrated hole. This disrupts the flow geometry, and the torch begins to “mow” or give an uneven distribution of paint. Clean duzu can only be special brushes of soft material or chemical solvents.
⚠️ Warning: Never leave paint in a spray gun tank for a long time, even if it is a lunch break. The dried paint inside the duse turns into stone, and it is almost impossible to clean it without damaging the calibrated hole.
Another mistake is the use of cheap Chinese duz unknown brands on expensive spray guns. The geometry of the hole can be broken already at the production stage, which will negate all the advantages of a quality tool. It is better to use original components or proven analogues from well-known manufacturers.
Care for the duz and extension of service life
The durability of the spray gun and the stability of the torch depend on the proper care of the spray head. After each change of material or completion of work, it is necessary to carry out a complete dismantling and washing. Dusa, needle and air cap should be cleaned from the residues of varnish or soil with special washes.
When assembling, it is important not to drag the duzyu. It is installed in the housing with a certain effort, often using a sealing ring. Excessive force when twisting can lead to deformation of the thread or the nozzle itself, which will cause air suction and disruption of the tool. The twisting is done by hand or with minimal effort of the key.
It is better to store the dusa in a lubricated state if the spray gun is not used for a long time. A thin layer of special lubricant for spray guns or petroleum petroleum oil will protect the precision parts from corrosion and oxidation. This is especially true for steel needles and duzes working with water-soluble paints.
Regular check of the condition of the sealing rings (gassing) on the duze and needle is a mandatory procedure. Worn gasket will lead to the fact that the paint will leak from under the nose of the spray gun, soiling the part and creating an emergency situation. Replacing a penny pad will save you from losing liters of paint.
The secret to cleanliness
Soak the removable spray gun head (dusa + cap) in an ultrasonic wash or solvent jar overnight after heavy work with the soil. This will remove the frozen particles from hard-to-reach places.
FAQ: Frequently Asked Questions
Can I apply a 1.3mm varnish?
Yes, the size of 1.3 mm is the standard for most varnishes. It provides excellent sprawl and gloss. An increase to 1.4 or 1.5 mm only makes sense if the varnish is very thick or you work in a cold room without heating.
Why does the spray gun “spit” with paint?
Most often this is a sign of clogging of the dusa or air channels. Also, the cause may be too thick paint for the selected size of the nozzle, a faulty needle (does not keep tightness) or a damaged sealing ring on the duse.
Which is better for metal: 1.3 or 1.4 mm?
For metallic preferable 1.3 mm, as it gives a smaller torch and uniform distribution of pigment. 1.4 mm can be used if you want to speed up the process, but it requires good skill to avoid stripes (apple).
How is the HVLP Dusa different from the usual?
Physically, duses can be interchangeable on the seat, but HVLP spray guns are designed to work with a certain air flow rate. It is important that the diameter of the duse matches the compressor performance and the type of gun to create the right vacuum.
Should I change the needle when replacing the duo?
Ideally, yes, as the needle and dusa rub each other in the factory to ensure tightness. However, in practice, only the duz knot is often changed. If after the replacement began to leak the paint, then you need to replace the needle.