Diluting car varnish is a process on which 80% of the final painting result depends. Even the most expensive two-component varnish can ruin the appearance of the car if not prepared correctly. In this article we will analyze not only the basic dilution proportions, but also the nuances that are silent in the manufacturers’ instructions: how the temperature in the garage affects viscosity, why HS varnishes require a different approach than MS, and how to avoid orange peel without expensive equipment.

You will find out what solvents compatible with different types of varnishes, how to check viscosity without a viscometer (spoiler: a regular ruler will do), and why professionals never dilute varnish “by eye”. We’ll also look at real cases where savings on thinner resulted in reworking the entire part. If you are painting your car for the first time or want to improve the result, these instructions will save you time, money and nerves.

1. Types of auto varnish: which one do you need?

Before diluting the varnish, determine its type - the proportions and even the tools depend on this. There are three main types used in automotive painting:

  • 🔹 HS (High Solid) — highly filled varnishes with a minimum solvent content (up to 30%). They give a thick layer that is resistant to UV rays, but require precise proportions. Popular brands: Sikkens Autoclear LV, PPG D8115.
  • 🔹 MS (Medium Solid) - universal varnishes with a solvent content of 40–50%. Easier to apply, but less durable. Examples: Mobihel Topcoat, Vika 2K.
  • 🔹 UHS (Ultra High Solid) — superfilled varnishes (solvent <20%). They are used in premium painting, but require professional equipment. For example, Spies Hecker Permahyd Hi-TEC 480.

Which one to choose? Ideal for garage painting MS-varnish — he forgives small mistakes in breeding. HS suitable if you have experience and a high-quality spray gun (for example, SATAjet 5000 with a nozzle of 1.3–1.4 mm). It is better not to use UHS varnishes without preparation: they “stand up” only under ideal conditions (temperature 20–22°C, humidity 50–60%).

Important: the type of varnish is always indicated on the can - look for the markings HS, MS or UHS. If it doesn't exist, it's probably cheap. nitro varnish (single-component), which is not suitable for body work.

📊 Which polish do you use most often?
HS (High Solid)
MS (Medium Solid)
UHS (Ultra High Solid)
I don't know what polish I have
Other

2. How to dilute varnish: solvents and their secrets

A solvent is more than just a diluting liquid. It affects:

  • 🔥 Drying time (fast solvents speed up the process, but can cause the varnish to “boil”).
  • 🌡️ Application temperature (in winter you need a “slow” solvent, in summer you need a “fast” one).
  • 🎨 Gloss and fluidity (the wrong solvent will give a cloudy finish).

Here is a table of compatibility of solvents with types of varnishes:

Varnish type Recommended solvent Proportion (varnish:solvent) Application temperature
HS Solvent HS (for example, PPG DX330) 2:1 or 4:1:1* (varnish: thinner: hardener) 18–25°C
MS Universal 2K solvent (for example, Mobihel 770) 3:1 or 2:1:1 15–30°C
UHS Special UHS solvent (for example, Spies Hecker 5330) 4:1:1 or 5:1:1 20–24°C

*Note: A 4:1:1 ratio means 4 parts varnish, 1 part thinner, 1 part hardener.

⚠️ Attention: Never use acetone or white spirit for breeding car polishes! They destroy the structure of the varnish, causing clouding and loss of shine. Also avoid solvents for nitro enamels - they are incompatible with two-component systems.

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If you are working below 15°C, add 5-10% drying retardant (for example, Sikkens Thinner Retarder). This will prevent the formation of “shagreen” (small irregularities).

3. Dilution proportions: how not to spoil the varnish

The most common mistake made by beginners is to thin the varnish “by eye”. Consequences: from drips to complete peeling of the coating. Here are the exact proportions for different tasks:

  • 🖌️ Base layer (first): 4 parts varnish: 1 part solvent: 1 part hardener (for HS). For MS - 3:1:1. This proportion gives good coverage without drips.
  • 🔍 Final layer (second): 2:1:1 (HS) or 2:1.5:1 (MS). Less solvent = more gloss, but harder to apply.
  • 🌡️ Hot weather (>25°C): increase the solvent by 10-15% (eg 4:1.5:1 instead of 4:1:1) to avoid "boiling".
  • ❄️ Cold (<15°C): reduce solvent by 10% and add retarder (eg 4:0.9:1 + 5% retarder).

How to measure proportions without scales? Use measuring containers with divisions (sold in auto repair stores). For example, for a ratio of 4:1:1:

  1. Pour varnish up to the mark 400 ml.
  2. Add solvent until 100 ml.
  3. Add hardener to 100 ml.

⚠️ Attention: If you are using different brands of varnish and solvent, do a test spray on the unwanted part. Some combinations (for example, PPG varnish + Mobihel solvent) may cause clouding or slow drying.

Prepare measuring containers|Check the temperature in the room|Select a solvent for the type of varnish|Wear a respirator and gloves|Stir the varnish in the jar before use-->

4. How to check viscosity without a viscometer

The ideal viscosity of the varnish is the key to an even coating. In professional workshops, viscometers are used (for example, DIN-4), but in the garage you can get by with improvised means:

Ruler method:

  1. Take a clean stick (for example, an ice cream stick) and dip it in the diluted varnish.
  2. Raise the stick vertically and time the time during which a drop of varnish drains 2–3 cm.
  3. Optimal time: 3–4 seconds for HS varnish and 2–3 seconds for MS. If the varnish drains faster, add solvent; if slower, let stand for 5–10 minutes (the solvent will partially evaporate).

Funnel method:

  • Take a plastic funnel with a 4–5 mm hole.
  • Pour varnish into it and note the time of complete expiration.
  • Normal: 12–15 seconds for HS, 8–10 seconds for MS.

If the varnish is too thick, it will form “lumps”; if it is liquid, it will flow. Ideal consistency resembles fatty milk.

What happens if you apply varnish of the wrong viscosity?

Too thick varnish will form “shagreen” (small irregularities) that will have to be sanded and polished. Too thin a varnish will flow, especially on vertical surfaces (doors, wings), leaving noticeable streaks. In both cases, the part will need to be repainted, which will increase material consumption by 30–50%.

5. Step-by-step instructions: how to dilute varnish correctly

Follow this algorithm to avoid errors:

  1. Varnish preparation: Stir the varnish in the jar with a wooden stick for 2-3 minutes. Don't shake the jar - it creates bubbles!
  2. Adding Hardener: Pour the varnish into a clean container and add hardener in proportion (see section 3). Stir for 1 minute.
  3. Filtration: Strain the mixture through paint filter (cell 190–220 µm) into another container. This will remove clumps and dust.
  4. Adding solvent: Pour in the solvent in a thin stream, stirring constantly. Do not pour the entire portion at once!
  5. Viscosity control: Check viscosity using one of the methods (section 4). Adjust if necessary.
  6. Defending: Let the polish sit for 10-15 minutes before applying. During this time, air bubbles will come out.

⚠️ Attention: If you are diluting varnish for metallic or mother of pearl, reduce the amount of solvent by 10%. These paints require a thicker consistency to “lay” the pigment evenly.

The temperature of the mixture should be 18–22°C. If the varnish is cold (for example, it was stored in the garage in winter), warm the jar in warm water (not higher than 30°C!) before diluting.

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The hardener is always added FIRST and the thinner LAST. Violation of this order leads to uneven hardening of the varnish and loss of shine.

6. Common mistakes and how to avoid them

Even experienced painters sometimes make mistakes. Here are the top 5 mistakes and their consequences:

Error Consequences How to fix
Too much solvent Smudges, long drying, cloudy gloss Let the varnish sit for 10–15 minutes or add hardener (no more than 5% of the volume)
Incompatible varnish and solvent Cloudiness, peeling, “boiling” of varnish Wash off the varnish with solvent and repaint with the correct combination
Poor mixing Uneven gloss, lumps, bubbles Strain the varnish through a filter and mix again
Low temperature operation (<10°C) The varnish does not “stand up”, remains sticky Move the part to a warm room or use an IR heater
Using expired hardener The varnish does not harden, remains soft Discard the mixture and use fresh hardener

Another common mistake is thinning the varnish in advance. A mixture of varnish, hardener and solvent has a “lifetime”:

  • 🕒 HS varnishes: 4–6 hours at 20°C.
  • 🕒 MS varnishes: 6–8 hours.
  • 🕒 UHS varnishes: 2–4 hours (due to high reactivity).

If you dilute the varnish in the morning and paint it in the evening, it may thicken or begin to polymerize in the container. Prepare the mixture immediately before work!

7. Professional advice for perfect results

We interviewed painters with over 10 years of experience and collected their life hacks:

  • 💡 For deep gloss: Add 5% to the final layer gloss additive (for example, Sikkens Autoclear Additive). This will enhance the “mirror” effect.
  • 💡 For complex parts (edges, corners): Thin the varnish 10% thicker than usual. This way it will not flow on vertical surfaces.
  • 💡 To save: The first coat can be applied with a ratio of 4:1.5:1 (more solvent), and the final coat with a ratio of 2:1:1 (more varnish).
  • 💡 For a “wet” effect: Use slow solvent (for example, PPG DX330S) and apply the varnish at a temperature of 22–24°C.

Another professional trick - "hot" breeding:

  1. Heat the varnish and solvent to 30°C (for example, in warm water).
  2. Dilute in standard proportions.
  3. Apply to the part, preheated with an IR lamp to 40°C.

This speeds up drying and improves spreadability, but requires experience - if overheated, the varnish may “boil”.

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If you paint plastic parts (bumper, mirrors), add 3–5% to the varnish plasticizer (for example, PPG Flex Additive). This will prevent cracks due to temperature changes.

FAQ: Answers to frequently asked questions

Is it possible to thin varnish without a hardener?

No. Two-component varnishes require a hardener for polymerization. Without it, the varnish will remain sticky and will not harden. The exception is one-component nitro varnishes, but they are not suitable for body work.

What is the difference between solvent for HS and MS varnishes?

Solvent for HS contains fewer aggressive components and evaporates more slowly so that a thick layer has time to form. Solvent for MS more “sharp” and disappears faster, since the varnish is thinner.

How to fix varnish runs?

If the drips are fresh (up to 10 minutes), carefully remove them with a cloth soaked in solvent. If the varnish has already hardened, sand the drip with sandpaper. P1200–P1500, then polish with a paste (eg 3M 50383).

Is it possible to mix polishes from different brands?

Theoretically it is possible, but the risk of incompatibility is high. If you decide to mix, do a test: mix a small amount of varnishes with their “native” hardeners and solvents, apply to a test surface and check after 24 hours for gloss and adhesion.

How many layers of varnish should I apply?

Optimal - 2 layers:

  • 1st layer: “wet on wet” (ratio 4:1:1, drying 5–10 minutes).
  • 2nd layer: “final” (proportion 2:1:1, drying 24 hours).

The third layer is only needed for UHS varnishes or when painting metallic.