Choosing the right finishing tool is not just a matter of convenience, but a critical step that determines the quality of the entire painting. Krascopult for polish It should ensure the most uniform distribution of the material without leakage, shaking or dust. A mistake in choosing can cost you a spoiled part, time to repaint and significant financial losses.
In the modern world of carpentry and carpentry, there are many spray technologies, each of which has its own advantages and disadvantages. From classical pneumatic systems to modern electrical models, the range is wide. Understanding the physics of the process and the characteristics of materials will help you make an informed decision.
In this article, we will discuss why the viscosity of the varnish dictates the choice of dusa, how air pressure affects the spray torch and what type of remote is suitable for your tasks. Deep immersion in technical details This will help avoid common mistakes of beginners and professionals.
Selection criteria: viscosity and type of material
The first thing that the master encounters when choosing equipment is the physical properties of the material. Lacquer, whether acrylic, polyurethane or water-based, has a certain viscosityThis directly affects the pressure and diameter of the nozzle. Too thick material in a spray gun with a small duo simply will not spray, but will "spit" drops.
Working with high viscosity varnishes, such as two-component polyurethanes, often requires preheating of the material or the use of a solvent. However, The best solution is the selection of a spray gun that can work with viscosity up to 600-700 s (on Ford's viscometer) without strong dilution.So as not to lose the protective properties of the coating.
It is also important to consider the volatility of the solvent. Fast-drying varnishes require special attention to the design of the tank and the air supply system to avoid drying the material in the channels during pauses in operation. Use of the teflon inside the tank greatly simplifies washing and reduces the risk of clots hitting the surface.
Remember that different varnish manufacturers may recommend different spraying options. Always check the product technical map (TDS) that lists the recommended duz diameters and operating pressure. Ignoring this data is the right way to get married.
Pneumatic systems: HVLP, LVLP and RP
Traditionally, the best choice for varnishing is considered pneumatic spray guns. They are divided into three main groups by spray technology, and each is suitable for different use cases. Understanding the difference between the two is key to saving material and time.
System system HVLP High Volume Low Pressure uses a large volume of air at low pressure. This provides a high material transfer ratio (up to 75%), which means less fog and saves expensive varnish. However, such pistols require powerful compressors with high performance.
Technology LVLP Low Volume Low Pressure works at even lower pressure and consumes less air. This is ideal for garage conditions where the compressor does not have a huge power. The quality of the torch is excellent, but the speed of work can be slightly lower due to a lower supply of material.
Systems RP Reduced Pressure or Trans-Tech is a compromise. They operate at medium pressure, providing a high application rate and excellent surface quality, but have a lower transport factor, creating more paint clouds in the air.
⚠️ Attention: Do not try to connect the HVLP spray gun to a weak compressor. The drop in pressure will lead to the fact that the varnish will lie in large drops, forming a shaking, which cannot be removed by polishing.
The choice between these systems often depends on the infrastructure you have. If you have an industrial screw compressor, HVLP will give you the best savings. For a mobile crew or a weak garage, LVLP is a lifesaver.
Diameter of duz and needles: technical nuances
The size of the duse (nozzle) is perhaps the most important parameter when choosing a tool for a specific material. For varnishes that usually have higher viscosity than base paints, enlarged holes are required.
The standard size for applying varnish is considered to be the diameter 1.3 mm or 1.4 mm. It is these values that allow you to create the perfect balance between the size of the droplet and the speed of departure. The use of 1.2 mm dusa is only possible for very liquid varnishes on a water basis or with strong dilution.
For thick soils or gel varnishes, duzes of 1.5 mm and even 1.7 mm may be required, but for finishing works this is already overkill, leading to overspending and overdeclines. The needle should perfectly match the diameter of the nozzle, ensuring tightness in the closed state.
- 🔹 1.2 mm - only for liquid varnishes on a water basis or metallized bases.
- 🔹 1.3. to 1.4 mm - "gold standard" for acrylic and polyurethane varnishes.
- 🔹 1.5 mm and above - for thick materials, soils or antigravel.
The quality of the needle and dusa manufacturing also plays a role. Stainless steel with high precision machining guarantees a stable torch throughout the life of the tool. Cheap Chinese counterparts often have microscopic defects that spoil the spray.
For varnish always choose a spray gun with a diameter of duz 1.3 or 1.4 mm, unless otherwise indicated in the technical map of the material. This will ensure the correct fragmentation of the material.
Electrical spray guns: is it worth contacting?
Electric models are often perceived as a budget alternative to pneumatics, but they are not always suitable for working with varnish. Their principle of operation (often air or airless) creates a specific structure of the torch.
Airless electric sprayers crush the material due to high pressure, pumping it through the nozzle. It is good for building paints and varnishes for wood, but for varnish It's dangerous. High pressure can lead to boiling of the solvent and the formation of pores in the coating.
Air-powered electric models (turbine) heat the air, which accelerates the evaporation of the solvent right at the exit of the gun. This can cause instant varnish drying in flight, leading to the effect of "orange peel".
However, for painting furniture, doors or small parts in garage conditions, modern electric models with pressure adjustment can give an acceptable result. The main thing is to choose the right viscosity material.
⚠️ Attention: Never use an electric spray gun to apply two-component varnishes with short lifespans unless you are sure of the ability to flush the system quickly. The frozen varnish inside the electrician is practically not removed.
If your choice fell on the electrician, pay attention to the availability of adjustment of the feed material and the shape of the torch. The absence of these settings makes the tool unsuitable for high-quality varnishing.
Why do electric guns heat the material?
In the design of electric spray guns, the motor is located close to the spray chamber. During prolonged operation, heat from the engine is transferred to the air or material, reducing its viscosity and accelerating the evaporation of the solvent, which is critical for varnishes.
Comparative Characteristics Table
To systematize the information and simplify the choice, let’s compare the main parameters of different types of spray guns in the context of working with varnish.
| Parameter | HVLP | LVLP | RP (Trans-Tech) | Electrical. |
|---|---|---|---|---|
| Pressure at the entrance (bar) | 2.0 - 2.5 | 1.5 - 2.0 | 3.0 - 4.0 | N/D (depending on model) |
| Coef. transfer (%) | 75% | 70% | 55% | 60% |
| Compressor requirements | Tall. | Medium/Low | Average. | Don't need it. |
| Quality of torch | Excellent. | Excellent. | Good. | Average. |
| Speed of operation | Medium | Low/Mediocre | Tall. | Low. |
The table shows that for professional work, where material savings and quality are important, low pressure systems are leading. Electric models remain for household use or specific tasks.
When choosing, you should also consider the weight of the tool. Metal canister pistols can be heavier, which tires the hand when working with large planes such as a roof or hood.
Set-up and preparation
Even the most expensive spray gun will not give a result without the correct setting. Before starting work, three main parameters must be adjusted: air pressure, material supply and the shape of the torch.
Pressure adjustment is carried out on the regulator built into the pistol or on the compressor pressure gauge. For varnish, pressure is usually set in the range 1.5 - 2.0 atm on the way out of the dusa. It is better to check this with a special test gauge.
The shape of the torch is adjusted by turning the upper regulator. For large planes, the torch is made as wide as possible (horizontal or vertical), for narrow parts - round. This allows you to control the amount of material applied.
☑️ Checklist for the preparation of the spray gun
It is important to use a moisture separator. Even microscopic drops of compressor oil that fall into the varnish will create craters ("fish eyes"), which will have to be eliminated by grinding and polishing the entire detail.
The application technique is also critical. The gun must be held perpendicular to the surface at a distance of 15-20 cm and move at a constant speed. The overlap of the strips should be 50-70%.
Tip: Before applying the varnish to the part, make a test shot on the test card or a piece of plastic. This will show whether the viscosity and pressure are correctly selected, and will avoid marriage at the main job.
Frequent errors and their consequences
Beginners often make mistakes that negate all efforts. One of the most common is the wrong distance to the surface. If you hold the gun too close, you will get stains; if you are far away, the varnish will dry in the air, and the surface will be rough.
The second mistake is ignoring interlayer exposure. The lacquer should be "laid down" for a certain time before applying the next layer. Violation of this rule leads to clouding, boiling of the solvent and loss of shine.
The third problem is poor filtering. Lacquer, especially two-component, may contain lumps or dust. The use of filters-funnels when pouring into the tank is a mandatory procedure.
⚠️ Attention: Do not try to save on a hardener for varnish. Mixing proportions must be kept to the gram, otherwise the coating will either not dry or become brittle and crack.
It is also worth mentioning the cleanliness of the room. Lacquer is a sticky substance that instantly glues any dust from the air. Work should be carried out in a clean, moistened room without drafts.
Tool care and storage
The life of your squirrel depends on how you take care of it. The lacquer, frozen inside the channels, turns into a stone that is extremely difficult to remove without damaging the seals.
Washing should be carried out immediately after the end of work. Use a suitable solvent (646, 647 or specialized washes). Run the solvent through the system, disassemble the needle and dusa, wipe them with soft rags.
Never soak a spray gun entirely in aggressive chemicals, especially if it has plastic or rubber parts. This will lead to swelling of the gaskets and loss of leakage.
With prolonged storage, it is recommended to lubricate the moving parts of the needle and trigger with a special oil for a pneumatic tool. Keep the gun is better in disassembled form or with a weakened needle spring so that it does not deform.
Regular inspection of the sealing rings and their timely replacement will avoid air sucking and unstable operation of the tool at a critical time.
FAQ: Frequently Asked Questions
Can I apply the paint to the paint?
Technically possible if the diameter of the duose is the same (1.3-1.4 mm). However, paint spray guns (bases) often have thinner needles (1.2-1.3 mm), which may not be enough for thick varnish. It is better to have a separate gun or wash it thoroughly between materials.
What pressure is needed for varnish?
The optimum pressure at the exit from the duse for most varnishes is 1.5 - 2.0 atmosphere (bar). The pressure at the entrance to the gun can be higher (2.0 - 2.5 bar) due to the resistance of the air head.
How to dilute the spray polish?
The varnish is diluted with the appropriate solvent specified in the instructions (usually 5-10% of the volume). For two-component varnishes, the varnish is first mixed with a hardener in the desired proportion, and then, if necessary, a solvent is added to achieve working viscosity.
Why does the varnish go down with a shaking?
The reasons can be different: too high pressure, a long distance to the surface, rapid evaporation of the solvent (hot weather or incorrect diluent) or insufficient viscosity of the material.
Do you need a powerful compressor for LVLP?
The main advantage of LVLP (Low Volume Low Pressure) is its low air consumption. For such pistols, a conventional garage compressor with a capacity of 200-250 liters per minute is often enough, making them ideal for home use.