Quality painting of the car or any other surface directly depends on how competently it was performed. spray-painting. Even the most expensive tool and premium materials will not give the expected result if the paint material (painting material) has the wrong consistency. Too thick a mixture will lead to the formation of shaven ("orange peel"), leaks and uneven spraying, whereas excessively liquid paint may not cover the surface or lose its color.
In the process of work, a painter must take into account many factors: the temperature in the paint chamber, the type of solvent used, the pressure at the exit of the nozzle and, of course, the initial viscosity of the material. Errors in the mixing stage are often fatal, as it is extremely difficult and costly to correct defects after polymerization of the coating. That is why understanding the physicochemical processes of dilution is a basic skill for any specialist.
In this article, we will discuss in detail all the stages of preparation, starting from choosing the right proportions and ending with the final filtration before pouring into the tank. You will learn how to use professional tools to control the quality of the mixture and what nuances should be considered when working with different types of enamel. Competent approach preparation The material is a guarantee that the finishing layer will lie flat, without defects and will last for years.
Solvent selection and material compatibility
The first and most critical step is the correct selection of diluent. Many beginners make the mistake of thinking that any solvent is suitable for any paint, but this is not the case. The chemical composition of the diluent must strictly correspond to the type of base of the paint material. For example, for acrylic enamels, base coatings base coat and varnishes use specific solvents that ensure proper evaporation and film formation.
In addition, it is necessary to take into account the temperature regime in which the work will be carried out. Solvents are divided into fast, medium and slow. Fast ones are used at low temperatures to speed up drying, but their application in the heat will cause the paint to boil on the surface. Slow, on the contrary, are needed in hot weather or with large volumes of work, so that the paint has time to spread, forming a glossy surface.
Using an inappropriate solvent can cause a chemical conflict: the paint can curl up right in the tank, become cloudy or lose adhesion to the ground. Always check the technical card (in the case of theTechnical Data Sheet) before mixing. There, the manufacturer clearly indicates the recommended types of diluents and their ratio.
⚠️ Warning: Never mix solvents from different manufacturers or batches in the same container. This can lead to unpredictable chemical reactions, changing drying times and defects in the finishing surface that cannot be eliminated by polishing.
It is also worth remembering about safety. Solvent vapors are toxic, so preparation should take place in a well-ventilated room or under the hood. Using a quality respirator with carbon filters is a requirement, not a recommendation.
Mixing proportions and working with viscometer
Determining the right viscosity is the heart of the preparation process. Viscosity characterizes the internal friction of the liquid and directly affects the quality of spraying. To measure this parameter, professionals use a viscometer (funnel), most often of the type DIN 4 or Ford 4. This simple tool is a funnel with a calibrated hole at the bottom.
The measurement process is as follows: completely immerse the viscometer in a container with paint, then sharply raise it and simultaneously start the stopwatch. The time it takes for the stream of paint to be interrupted and turned into separate drops is the viscosity sought in seconds. For most spray gun with a nozzle of 1.3-1.4 mm, the optimal viscosity is 18-22 seconds, but the exact values are always indicated in the technical card.
If the leakage time exceeds the norm, it is necessary to add the solvent in small portions, thoroughly stirring the mixture after each additive and conducting measurements again. Do not pour the diluent "on the eye", as it is easy to overdo it, and then you will have to add another portion of paint, violating the general recipe. Accuracy is important up to grams, especially when coloring complex colors.
For ease of perception, we give a table of indicative viscosities for various materials when using a standard spray gun:
| Type of material | Duse diameter (mm) | Optimal viscosity (sec, DIN 4) | Type of solvent |
|---|---|---|---|
| Acrylic enamel (2K) | 1.3 – 1.4 | 18 – 22 | Acrylic, 20-30% |
| Base layer (Base Coat) | 1.3 – 1.4 | 16 – 19 | Special for the base |
| Lac (Clear Coat) | 1.3 – 1.5 | 20 – 24 | It's in the kit. |
| Sound filler | 1.6 – 2.0 | 25 – 35 | Acrylic, 10-20% |
It is worth noting that viscosity is not a constant value. It depends on the temperature: the colder the material, the thicker it is. Therefore, all components (paint, hardener, solvent) should have the same temperature, preferably room temperature (about 20 ° C), before mixing.
Technology of mixing components
The correct sequence of addition of components plays an important role in obtaining a homogeneous mixture. The standard procedure begins with opening a can of paint. Even if the paint (looks) uniform, the pigment could settle to the bottom during storage. Therefore, the first step is a thorough mixing of the main component in the factory container.
Next, you need to pour the required amount of paint into a measuring glass. The measured glasses have a calibration, which allows you to observe exact proportions without using weights. First, paint is poured into the glass, then a hardener is added (if the material is two-component) and only at the end - a solvent. This sequence makes it easier to control the process and avoid overflows.
☑️ Checklist for mixture preparation
After adding all the ingredients, the mixture must be mixed again intensively. The movements must be circular, with the mass lifted from the bottom to ensure that all chemical components are fully interoperable. Pay special attention to the corners of the glass - there is often unmixed paint.
It is important to remember the “pot life” of the mixture. After adding the hardener, an irreversible chemical polymerization reaction is triggered. In different materials, this time ranges from 30 minutes to 3-4 hours. Prepare paint for the future, for a few days ahead, categorically impossible - it will turn into a gel and become unusable.
⚠️ Note: If you use a paint with a metallic or mother of pearl effect, the lifespan of the mixture may be shortened due to the peculiarities of the aluminum pigments. Do not leave the prepared mixture in an open glass for more than 20-30 minutes without stirring, otherwise the components may be stratified.
Filtration – Protection against defects
Even if you work in a perfectly clean room, the paint may contain extraneous inclusions: clots of pigment, dust particles that fell from the lid, or film formed during the previous opening. The hit of any such particle in the spray gun is guaranteed to lead to clogging of the nozzle or the appearance of craters and "spitting" on the painted surface.
Filtration is therefore a mandatory step. For this purpose, special funnels with replaceable nylon or metal mesh are used. The size of the grid cell should correspond to the diameter of the duse of the spray gun. For finishing, a grid of 125 microns (125 microns) is usually used, for soils you can take a larger one - 190 microns.
The process is simple: install a funnel on the neck of the spray gun tank, insert a filter and gently pour the prepared mixture. If the paint is very thick, you can slightly help it with a wooden stick, but do not press hard so as not to break the net. After use, the filter is discarded, reuse is not allowed.
What to do if the paint still hit the nozzle?
If you notice that the spray torch is broken (a “spitting” jet or displacement to the side appears), do not try to clean the nozzle with a finger or rag directly into the parts. Remove the spray gun head, wash it in a solvent and blow it with compressed air. The use of sharp objects (needle, wire) to clean the calibrated hole is prohibited - this will permanently spoil the geometry of the torch.
Some craftsmen neglect filtration if the paint is new, but practice shows that factory packaging is not always sterile. Spending 10 seconds on filtration can save hours of work on repairing defects and repainting parts.
Setting up the spray gun for prepared paint
Once the paint is prepared and filtered, you need to configure the tool itself. Setting the spray gun is a balance between the pressure at the entrance, the width of the torch and the supply of material. These parameters are individual for each material and even for each specific can of paint.
You should always start setting up with a test on paper or cardboard. Spray the paint and evaluate the result. If large drops (spitting) are visible, then the paint is too thick or the pressure is too low. If the paint is laid dry, dusty film - the pressure is too high or a lot of solvent is added. The ideal footprint should be uniform, with a light gloss (for base) or a wet surface (for varnish).
- 🎨 Breadth of torch: It's controlled by the top screw. For large planes, open the torch as much as possible, for bottlenecks or arches - narrow.
- 💨 Pressure: It is regulated by a screw on the handle or a regulator on the manometer. The standard range for HVLP is 2.0-2.5 bar at the inlet, for LVLP - slightly higher.
- 💧 Submission: It's controlled by the bottom screw. Open the feed completely to work with large volumes, so as not to suffocate the system.
Remember that the viscosity of the paint directly affects the required pressure. A thicker material requires more pressure for high-quality spraying, but you can not overdo it, otherwise fog and overconsumption of the material will increase.
Conduct a test spray at the same temperature and humidity at which the main painting will take place. A change in environmental conditions may require (adjustment) pressure or amount of solvent.
Frequent errors and troubleshooting
Even experienced painters sometimes face problems when painting. Most often they are associated with improper preparation of paint. Let’s look at typical scenarios and ways to solve them.
One of the most common problems is dyes. This occurs when the solvent evaporates too quickly, forming bubbles that burst on the surface, leaving craters. The reason lies in using too fast solvent in a hot room or applying too thick a layer.
The other extreme. shadrane ("orange peel"). If the surface after drying resembles the peel of an orange, then the paint was too viscous, poorly mixed or applied under insufficient pressure. In this case, the material does not have time to spread before polymerization.
⚠️ Never try to stretch the life of paint by adding fresh solvent to an already mixed compound that has stood for more than an hour. This disrupts the chemical balance of the hardener, and the coating may remain sticky forever or lose strength.
There's also a problem. turbidity (white coating). This often happens at high humidity, when moisture condenses into a fresh layer of varnish. Using a slow ("anti-rain") solvent helps avoid this effect, as it evaporates more slowly and gives the moisture time to evaporate.
90% of all paint defects (shagrins, craters, leaks) are eliminated by correct adjustment of viscosity and cleanliness in the working area. Don’t waste time preparing the mixture.
FAQ: Frequently Asked Questions
Can acetone be used instead of a special solvent?
It's not recommended. Acetene is a very aggressive and fast solvent. It can cause clouding of acrylic paints, violation of adhesion and drying too quickly, which will lead to shaking. Use only solvents recommended by the paint manufacturer.
How long can you store diluted paint?
Storage time depends on the type of material. Single-component paints (nitro, some acrylics) can be stored in a tightly closed container for several weeks, if a film has not formed. Two-component mixtures (with hardener) are viable from 30 minutes to 4 hours. After this time, the mixture begins to thicken and becomes unusable.
Why does the paint flow (forms the leaks)?
The main reasons are too liquid paint (lots of solvent), too long distance from the spray gun to the part, slow movement of the hand or insufficient air pressure. Also, leaks can occur when the next layer is applied to the previously insufficiently dried.
Do I need to heat the paint before using it?
Under standard conditions (20°C) no heating is required. However, in cold rooms or when working with viscous soils, heating up to 25-30 ° C can improve spreadability. The main thing is not to overheat the material, otherwise it will quickly evaporate and change the viscosity right in the tank.
How to clean the spray gun if the paint dried inside?
If the paint dries inside the channels, you will need a complete dismantling of the tool and soaking the metal parts in a special cleaner or acetone (for metal parts). Plastic elements can not be wet in aggressive chemistry. It is better not to dry and wash the tool immediately after work.