Choosing the right paintwork is not just a matter of aesthetics, but a critical body repair step that determines how long your car will look like new. Many motorists and even novice painters underestimate the role of the finishing layer, believing that the main thing is the color of the base. However, it is precisely varnish It takes the main blow of the external environment: ultraviolet, acid rain, hail, chemical reagents from roads and mechanical scratches.
The modern market offers many options, from budget acrylic compounds to professional two-component systems with increased hardness. An error in choice can cost you to repaint after six months, when the coating becomes cloudy or covered with a grid of cracks. In this article, we will discuss in detail the chemical composition, the difference between HS, MS and UHS products, and also help you determine which material is suitable for your case.
Before you go to the store, you need to understand the basic principle: varnish is a polymer, which, after mixing with a hardener and evaporating the solvent, forms a strong protective film. It is the quality of this film that determines the depth of color and durability of the entire paint system. Let’s move on to the technical details that distinguish professional from amateur coverage.
Chemical composition and types of car varnishes
The basis of any high-quality varnish for body repair is polyurethane or acrylic. It is these components that provide the necessary elasticity and adhesion. However, a key classification parameter is the dry residue content, which determines how much substance will remain on the body after the volatile fractions have completely dried and evaporated.
The most common category is labeled materials. HS (High Solid). These are varnishes with a high dry residue content, usually between 60% and 70%. They create a thick, saturated layer, spread perfectly and give a deep gloss. It is HS systems that are most often recommended for local repair and painting of whole elements, as they forgive small errors in application and provide a great appearance.
There are also lacquers MS (Medium Solid)which contain less dry matter and more solvents. They are cheaper, but give a smaller layer and require more careful application, as they are prone to shrinkage. For professional body restoration today, the de facto standard is HS-composites, while MS is a thing of the past or used for inexpensive commercial vehicles.
Always pay attention to the date of production of the varnish. Even a closed jar has an expiration date, and the use of expired material can cause the coating to not dry or cloud.
It is important to note that the chemical formula affects not only the luster, but also the compatibility with the base enamel. Some aggressive solvents in cheap varnishes can “raise” the base, creating defects that cannot be eliminated by polishing. Therefore, using materials from one system or proven compatible brands is not marketing, but a technical necessity.
Hardness and Elasticity: Finding the Perfect Balance
One of the most common questions when choosing materials is: what is more important, hardness or elasticity? The hardness of the lacquer determines its resistance to scratches from washing, branches and sand. Elasticity is the ability of the coating to stretch and contract together with the metal of the body at temperature changes and vibrations, without cracking.
Too hard a lacquer can be fragile. When hit hard by a stone or hail, such a coating will not extinguish the energy of the impact, but will crack, often along with the base layer of paint. On the contrary, too soft varnish will be easy to polish, but quickly covered with small scratches-spiders (swalls) after the first contact wash.
⚠️ Note: Do not try to mix the varnishes of different manufacturers with hardeners of other brands. Chemical reactions can be unpredictable, resulting in no drying or detachment of the coating after a short time.
Modern technologies have made it possible to create materials that combine high hardness (on a scale or pendulum method) and excellent elasticity. These varnishes are often labeled as “Anti-Scratch” or have special ceramic type additives. However, it is worth remembering that even the hardest varnish does not make the body bulletproof, it only increases the threshold of resistance to microdamage.
For areas with increased vibration or deformity, such as bumpers, experts recommend using standard elastic varnishes or adding special ones to them. plasticizer. This will prevent cracks in the places of folds or in light impacts, which are common for bumpers.
Application technologies: HS, UHS and drying speed
The application technology directly affects the time that the car will be in the chamber, and the final surface quality. In addition to the HS and MS, the compositions appear on the market. UHS (Ultra High Solid). They contain even more dry residue, which allows you to apply a quality coating in fewer layers, saving material and time.
The drying speed also varies. There are varnishes of fast, normal and slow drying. The choice depends on the temperature in the paint chamber and the size of the part being painted. For large elements such as a roof or hood, it is better to use varnishes with a normal or slow hardener so that the material has time to spread, forming an orange peel of minimal size.
Fast varnishes are good for small parts or work in the cold season, but they require high speed painter. If you hesitate, the material can begin to grasp even in the spray gun, which will lead to texture defects. The correct selection of solvent and hardener under ambient temperature is the key to success.
When using two-component systems, it is critical to observe mixing proportions. They are usually 2:1 or 4:1 (varnish to hardener). Violation of these proportions in the direction of increasing the hardener will make the coating fragile, and the reduction will not allow the varnish to gain full strength and chemical resistance.
Comparison of characteristics of popular systems
To simplify the choice, let’s compare the main types of varnishes on key parameters. This table will help you understand what material is suitable for your tasks, whether it is a complete repainting of a luxury car or a budget bumper repair.
| Parameter | MS (Medium Solid) | HS (High Solid) | UHS (Ultra High Solid) |
|---|---|---|---|
| Dry residue content | 30-40% | 60-70% | 75-85% |
| Number of layers | 3-4 | 2-3 layers | 1.5-2 layers |
| Depth of shine | Medium | Tall. | Very high. |
| Material consumption | High-pitched | Medium. | Low. |
| Recommended application | Budgetary repairs | Standard of quality | Premium segment |
As can be seen from the table, the transition to more modern systems (HS and UHS) allows not only to improve the visual effect, but also to reduce the overall consumption of materials, which in terms of the cost of work often makes them more profitable, despite the higher price per liter.
In addition, modern varnishes often have the function of self-healing small scratches under the influence of heat (effect). Self-Healing). This is achieved due to the special structure of polymer chains, which, when heated by the sun or hot water, “tighten” microdamage. This option becomes the standard for mid- and upper-class cars.
What is the "sharrai effect"?
Shagrin is the texture of the surface of the varnish after drying, resembling the peel of an orange. The less shavern, the smoother and mirrored the varnish looks after polishing. The expensive varnishes have a minimum of shavern initially.
Surface preparation and lacquering process
Even the most expensive lacquer will not hide the mistakes of preparation. Before applying the finish layer, the base should completely dry (observance of interlayer drying), and the surface should be cleaned of dust and defatted with antisilicone. Any dust that is stained under the varnish will become a noticeable defect.
The lacquering process requires cleanliness. The camera should be warmed up, the pressure in the spray gun is adjusted according to the manufacturer's recommendations (usually 2-2.5 atmospheres at the exit of the torch). The first layer is applied thin, "dust" to provide adhesion. The subsequent layers are laid wet in wet with an interlayer exposure of 10-15 minutes.
- 🎨 First layer: thin, binding, without leaks.
- 💧 Second layer: main, wet, glossy, provides spreading.
- ✨ Third layer (optional): to enhance depth and eliminate transitions at the boundaries of the part.
It is important to control the angle of the torch and the distance to the surface (usually 15-20 cm). Movements should be smooth and uniform. Sharp stops of the hand guarantee the formation of flows, which then have to be long and painfully removed by grinding.
☑️ Pre-varnishing control
Lacquer defects and methods of their elimination
Various problems may arise in the process of work. One of the most common is “boiling” or bubble formation. This happens if the solvent does not have time to leave the lower layers when the upper layer has already grasped. Often the reason lies in too fast hardener or high drying temperature.
Mattiness or "milky way" is another unpleasant defect that occurs when moisture enters the compressor air intake or when varnishing in high humidity conditions. The moisture condenses into the layer of lacquer, making it cloudy. This is treated only by complete reworking and reworking of the part under normal conditions.
⚠️ Note: If you notice a defect immediately after application, do not try to polish it immediately. Let the varnish gain full hardness (usually 24 hours at 20°C or 1 hour at 60°C in the chamber), otherwise you will simply smear the material.
Flows and influxes are the lot of beginners, but they also happen to pros. If the flow is small, it can be gently sanded with an abrasive P2000 after complete polymerization and polished. Deep streams require cutting the varnish to the base and local polishing, which is more complicated and requires high qualification.
Polishing and care for new coating
Once dry, a new varnish often has a light shaking or dust that requires finishing. The polishing begins with abrasive P2000 or P3000 to cut the shaking, and ends with fine polished pastes to restore transparency and shine. It is important not to overdo it and not to wipe the varnish to the base, especially on the sharp edges of the body.
To prolong the life of the lacquer layer, it is recommended to use protective compositions. It can be waxes, sealants or ceramic coatings. Ceramics creates an additional hard layer that takes on chemical attacks and ultraviolet light, keeping the main varnish intact.
Regular washing without the use of aggressive chemicals and hard brushes is a guarantee that the varnish will remain glossy for many years. The use of a two-phase shampoo and a soft microfiber mitten minimizes the appearance of new scratches.
The quality of preparation and compliance with the application technology is more important than the brand of varnish. Cheap material applied by technology will look better than expensive, applied with violations.
In conclusion, the choice of car varnish is a balance between budget and expected result. For yourself and for sale, it is better to choose proven HS-systems of well-known brands, such as: PPG, Sikkens, Mobihel or Body. Savings on lacquer can lead to expensive rework, so trust only quality materials and professional execution.
Can I paint a matte paint with glossy varnish?
No, you can't. Matte paints (Matte Base) have a special structure that scatters light. If you cover them with a regular glossy varnish, the effect of matteness will disappear and the surface will become glossy, often with spots. For matte bases there are special matte varnishes.
How much does the varnish dry at room temperature?
The drying time of the dust is 20-40 minutes. Full polymerization and polishing are possible after 12-24 hours at a temperature of 20 ° C. Accelerated drying in the chamber at 60°C reduces the time to 30-40 minutes.
Do I need to grind the base before the varnish?
If the base dried less than 12-24 hours, it is not necessary to grind it, it is enough to degrease. If the base has dried for longer (for example, a few days), it is recommended to pass it with a soft abrasive (P4000-P5000) or a special scotch bright to improve adhesion, since the base may have dusted and lost its adhesive properties.
What to do if the polish does not dry?
The reasons can be different: incorrect proportion of the hardener, low temperature, old or poor-quality hardener. If more than 24 hours have passed and the varnish is sticky, the only way out is to wash everything with solvent to metal and start anew, having previously eliminated the cause.