The quality of a car's paintwork depends 70% on the correct preparation of materials. Even the most expensive two-component varnish from Sikkens or PPG will lose its properties if it is not diluted correctly. Errors at this stage lead to loss of shine after 3-6 months, the appearance of “orange peel”, streaks or even peeling of the coating. This article contains the current proportions for diluting car varnishes in 2026, taking into account temperature, humidity and application method.
We analyzed technical data sheets of 15 leading manufacturers (including Vika, Mobihel, Duxone and Spies Hecker) and systematized the data into convenient tables. We paid special attention to the nuances that even professionals often miss: how it affects the proportions thixotropy of varnishwhy “universal” thinners spoil the result, and how to adjust the viscosity HVLP-gun or airless spray. If you are working with acrylic varnishes or HS systems (high solid), here you will find precise recommendations taking into account their specifics.
Why dilution proportions are critical for auto varnish
After dilution, the varnish must meet three key parameters:
- 🔹 Viscosity - measured in seconds using a viscometer (usually 18-22 seconds at 20°C for standard systems). A varnish that is too thin will cause drips, while a thick varnish will cause shagreen.
- 🔹 Solvent volatility — determines the drying speed. Slow thinners are used at high temperatures, fast thinners in cold shops.
- 🔹 Hardener compatibility - some combinations (for example, Vika + non-original hardener) require adjustment of proportions by 5-10%.
Manufacturers indicate basic proportions on the cans, but they are designed for ideal conditions: temperature +20°C, humidity 50-60% and professional equipment. In reality:
- 🌡️ At +15°C, the varnish thickens by 15-20% - the share of thinner needs to be increased.
- 💦 At humidity levels above 70%, “slow” thinners are used to avoid clouding.
- 🔫 For
HVLP-guns (low pressure) the varnish is diluted more than forRP-pistols.
An error of 5% in the thinner can result in the coating taking 2 times longer to dry or, conversely, not having time to spread over the surface. For example, when applying Mobihel Helios with a hardener ratio of 1:1 instead of the recommended 2:1 (varnish:hardener), the gloss is reduced by 30% after just a month of use.
Table of proportions for popular brands of varnish (2026)
Below is an updated table for the varnishes most in demand in Russian car repair shops. Data verified against manufacturers' technical data sheets (available on official websites Vika, PPG, Sikkens).
| Varnish brand | System type | Proportion (varnish:hardener:thinner) | Recommended thinner | Viscosity (sec, 20°C) |
|---|---|---|---|---|
| Vika 2K | Standard acrylic | 2:1:0.5-1.0 | Vika 540 (universal) | 18-20 |
| Mobihel Helios | HS (high solid) | 2:1:0.3-0.7 | Mobihel 770 (fast) | 22-24 |
| Sikkens Autoclear LV | Low viscosity | 2:1:0.8-1.2 | Sikkens Thinner 208 | 16-18 |
| PPG D8115 | Urethane | 4:1:1.5-2.0 | PPG DT870 (slow) | 20-22 |
| Duxone 2K | Standard | 3:1:0.5-1.0 | Duxone 5000 | 19-21 |
⚠️ Attention: For varnishes HS (high solid) the volume of thinner is always less than for standard systems, since they initially contain more dry residue. Exceeding the recommended proportion of thinner by more than 10% leads to a decrease in coating hardness by 20-30% (test data PPG 2023).
If you are working with varnish Sikkens Autoclear LV, use a viscometer DIN 4 — its readings are more accurate for low-viscosity systems than the standard one Ford 4.
How to adjust proportions depending on temperature
The temperature in the spray booth is a key factor influencing the choice of thinner and its quantity. Manufacturers divide thinners into three types based on evaporation rate:
- 🐢 Slow (for +25°C and above) - contain high-boiling solvents (for example,
xylene). - ⚡ Average (for +18-25°C) - universal, suitable for most conditions.
- ❄️ Fast (for +10-18°C) - contain easily evaporating components (for example,
acetone).
Below is a correction table for acrylic-based varnishes (for example, Vika 2K or Duxone):
| Temperature (°C) | Thinner type | Proportion adjustment (from base) | Drying time (before dust) |
|---|---|---|---|
| 10-15 | Fast | +10-15% | 15-20 min |
| 16-20 | Medium | No changes | 10-15 min |
| 21-25 | Slow | -5-10% | 5-10 min |
| 26-30 | Very slow | -15-20% | 3-5 min |
🔴 Critical error: The use of "fast" thinner at temperatures above +25°C leads to microporosity varnish - pores invisible to the eye are formed on the surface, which later absorb dirt and moisture. This reduces the service life of the coating by 40% (study BASF, 2022).
Check the temperature in the chamber with a thermometer (do not rely on “feelings”)
Select thinner from the table above (do not use "universal"!)
Measure out the components using weighing dispensers (the error of the eye is up to 30%)
Mix the varnish with a mixer at low speed (600-800 rpm) for 3-5 minutes
Check viscosity with a viscometer DIN 4 or Ford 4
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Dilution features for different application methods
The spraying method directly affects the required viscosity of the varnish. For example, for HVLP-guns (low pressure, high air volume) the varnish should be thinner than for traditional RP-pistols. This is due to the fact that HVLP creates less pressure at the outlet, and drops of varnish break up less easily.
Viscosity recommendations for different systems:
- 🔫 HVLP (1.0-1.3 bar): 16-18 sec.
DIN 4(for example, for Sikkens Autoclear LV). - 🔫 RP (2.0-2.5 bar): 18-20 sec.
DIN 4(for example, for Vika 2K). - 🔫 Airless spray: 22-25 sec (varnish should be thicker due to high pressure).
For HS varnishes (high solid) viscosity is always higher - for example, Mobihel Helios applied within 22-24 sec, even after HVLP. This is due to the high content of solid particles (up to 70% versus 40-50% in standard varnishes).
What happens if you apply HS varnish with a viscosity of 18 seconds?
At reduced viscosity HS varnishes lose thixotropic properties - they do not “spread” evenly, but form waves and drips. In addition, the thickness of the layer is reduced, which leads to insufficient protection from UV radiation (the coating will fade after 1-2 seasons).
⚠️ Attention: When working with HVLP- never use thinners based on guns butyl acetate - they evaporate too quickly, which leads to dry spray ("sand" effect). Thinners with high contents are suitable for such systems. xylene or solvent (for example, PPG DT870).
Typical mistakes when thinning varnish and their consequences
Even experienced painters make mistakes that ruin all their efforts. Here are the most common:
- 🔢 Inaccurate hardener proportions:
- Less than normal → the varnish does not harden completely and remains sticky.
- More than normal → the coating becomes brittle and prone to chipping.
Example: B Vika 2K with a hardener ratio of 1:1 instead of 2:1, the hardness of the coating drops by 40% (on the scale
Koenig). - 🌡️ Ignoring temperature:
- Using a “slow” thinner at +10°C → the varnish does not have time to spread, shagreen and matte spots form.
- 🔄 Insufficient mixing:
- The hardener and thinner may not be evenly distributed, resulting in an uneven gloss.
- ⏳ Exceeding the pot life of the mixture:
- Varnishes based on isocyanates (for example, PPG D8115) begin gelation after 4-6 hours. Application after this period leads to defects.
🔹 How to avoid mistakes:
- 📏 Use weighing dispensers (not volumetric!) - the density of hardeners and thinners is different.
- ⏱️ Mix the varnish 15-20 minutes before application - this gives time for degassing (air bubbles leaving).
- 🧪 Check viscosity after mixing — when mixing components, the viscosity may change.
The most dangerous mistake is using incompatible components. For example, a hardener based HDI (hexamethylene diisocyanate) is incompatible with varnishes requiring IPDI-hardener. This leads to complete loss of adhesion after 1-2 months.
How to dilute varnish for repairing local areas
When partial renovation (for example, after removing chips or scratches) the proportions of dilution differ from full painting. Here are the key tasks:
- 🎨 Shine match — the varnish on the repaired area should merge with the original coating.
- 🔍 Minimum shrinkage — when drying, the varnish should not “sag”, exposing the boundaries of the repair.
- 🛡️ Good adhesion - especially important when applying to old varnish without complete sanding.
Recommendations for local repairs:
- Use slow thinners even at normal temperatures - they give the varnish more time to spread.
- Increase the proportion of thinner by 10-15% compared to full painting (for example, for Vika 2K: 2:1:1 instead of 2:1:0.5).
- Apply varnish in 2-3 thin layers with interlayer drying for 5-10 minutes (depending on temperature).
- For transitions (shading) use thinner with additive
retarder(drying retardant).
⚠️ Attention: For local repairs, never use HS varnishes (high solid) in small areas - they give a layer that is too thick to be noticeable. Optimal choice: standard acrylic varnishes with high spreadability (for example, Sikkens Autoclear LV).
Frequently asked questions about car polish thinning
Is it possible to thin the varnish without a hardener?
No, this will cause the coating to never harden completely. The hardener starts the polymerization reaction; without it, the varnish will remain sticky and easily damaged. Exception - one-component varnishes (for example, for temporary protection), but they are not used in professional painting.
What is the universal thinner?
There are no “universal” thinners - each varnish requires a specific composition. However, for most acrylic systems a thinner based on xylene and butyl acetate (for example, Vika 540). For HS varnishes and urethane systems require specialized thinners.
What happens if you add too much thinner?
Exceeding the amount of thinner by more than 20% leads to:
- Reduced coating hardness (easily scratched).
- Reduces shine (dullness appears).
- Increased drying time by 1.5-2 times.
- Increased sensitivity to UV radiation (fading after 6-12 months).
How to check viscosity without a viscometer?
As a last resort you can use stick method:
- Dip a clean wooden stick into the varnish.
- Lift it and time the time it takes for the drop to come off.
- The optimal time is 3-4 seconds for standard varnishes.
However, this method gives an error of up to 30%, so it is better to get a viscometer DIN 4 (costs from 500 rubles).
Is it possible to mix varnishes from different manufacturers?
Strongly not recommended. Different manufacturers use different resins and hardeners. For example, varnish Vika based on acrylic resin may not polymerize with hardener PPG, designed for urethane resins. Consequences: peeling, clouding or sticky surface.