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The clear coat is the layer that determines a vehicle's final appearance and the paint system's resistance to external influences, so the choice between MS and HS clear coat has a direct impact on both quality and workshop productivity. Both types are based on 2K acrylic polyurethane, but they differ markedly in solids content, application behaviour and cost structure. In this guide we compare the differences using concrete criteria and discuss which is the better choice for which job.
What Do MS and HS Mean?
MS (medium solids) denotes a clear coat with a medium solids content, and HS (high solids) one with a high solids content. The solids are the part that remains on the surface and forms the film once the clear coat has dried; the rest is solvent, which evaporates during application and drying.
- In a ready-to-use MS clear coat, the solids content is typically in the range of 40–50% by weight.
- In HS clear coats, this figure is typically 50–60%, rising even higher in some formulations.
This difference may look small at first glance, but its consequences are significant. At the same wet film thickness, an HS clear coat leaves more material on the surface and releases less solvent, so its volatile organic compound (VOC) emissions are lower. UHS (ultra-high-solids) systems, with an even higher solids content, take the same approach a step further.
Even so, solids content alone does not determine quality. Resin quality, UV-protective additives and the right choice of hardener are at least as important; a well-formulated, correctly applied MS clear coat can give a better result than a poorly applied HS clear coat.
HS vs MS Clear Coat Comparison Table
| Criterion | MS clear coat | HS clear coat |
|---|---|---|
| Solids (ready to use, typical) | 40–50% | 50–60% and above |
| Solvent / VOC content | Higher | Lower |
| Typical total dry film thickness | 40–50 µm | 50–60 µm |
| Typical number of coats | 2–3 coats | 1.5–2 coats |
| Gloss and depth | High gloss; an extra coat may be needed for depth | Fuller, deeper appearance |
| Polishing | Possible; needs care with a thin film | Generous polishing margin thanks to the thick film |
| Application tolerance | More forgiving, easy flow control | Requires correct gun set-up and coat discipline |
| Typical use | Spot and panel repairs, fleet and budget work | Full resprays, work where appearance comes first |
| Cost and efficiency | Usually lower price per litre; more coats needed | Higher price per litre; fewer coats, shorter booth time |
The values in the table are ranges generally regarded as typical in the industry; for exact values, refer to the Technical Data Sheet (TDS) of the product you are using.
As regards drying and polishing, both types can be oven-baked or left to air-dry. On baked surfaces, polishing should begin once the part has cooled; with air drying, only once the clear coat has fully cured. Exact times are given in the product's TDS. The thick film of an HS clear coat gives more tolerance when polishing, but this does not mean it can be polished any sooner.
HS Clear Coat: Strengths and Points to Watch
High-solids clear coats such as ZN-330 2K Acrylic HS Clear Coat reach the target film thickness in fewer coats. This saves considerable time, particularly on full resprays and in workshops where the booth is in heavy use.
Advantages
- High film build in few coats, with a full, deep appearance
- More material to polish into, making it easier to correct dust nibs and orange peel
- Lower solvent emissions
- Sufficient film thickness helps preserve the clear coat's UV protection and outdoor durability
Points to Watch
- Because the viscosity is higher, the spray gun nozzle size and air pressure must be set according to the TDS; insufficient atomisation leads to orange peel.
- Laying on heavy coats out of MS habit increases the risk of runs. The typical procedure is a medium closed coat first, followed after the flash-off time by a second, full closed coat.
- Pot life and flash-off times change as the temperature rises; do not go outside the temperature ranges given in the TDS.
MS Clear Coat: Strengths and Points to Watch
Thanks to their higher solvent content, MS clear coats such as ZN-320 2K Acrylic MS Clear Coat flow out easily over the surface and adapt more readily to different application habits. This makes them a practical solution for spot repairs, single-panel jobs and fast-turnaround workshop work.
- Advantages: Easy application, wide application tolerance and a generally more economical cost per litre.
- Points to watch: Usually 2–3 coats are needed to reach the target film thickness. If the flash-off time (typically 5–10 min) is not observed, there is a risk of solvent entrapment, loss of gloss and pinholes. A film that ends up too thin also increases the risk of polishing through to the basecoat.
In spot repairs, the clear coat has to be melted in at the blend zone. The easy-flowing MS clear coat makes it easier to work in a controlled way on such small areas, and using the blending (fade-out) thinner specified by the system in the blend zone helps to make the boundary between the old and new clear coat invisible.
Choosing the Right Hardener and Thinner
Every clear coat works with a hardener balanced to its own resin structure. HS and MS hardeners are therefore not interchangeable:
- ZN-330 HS clear coat is used with ZN-440 2K HS Hardener,
- ZN-320 MS clear coat with ZN-430 2K MS Hardener.
The wrong hardener upsets the chemical balance between resin and hardener. The result can be a film that stays soft and has poor chemical resistance or, conversely, one that is brittle. For thinning, use only the acrylic thinner specified for the system; the thinner addition for clear coats is usually in the range of 5–10%. Measure the ratios by volume using a graduated mixing cup. In addition:
- Close the hardener tin immediately after use; isocyanate-based hardeners react with moisture in the air.
- Use up the mix you have prepared within its pot life.
- When working with products containing isocyanates, use the respiratory protection (preferably a fresh-air-fed mask), gloves and eye protection specified in the product's Safety Data Sheet (SDS).
Which One Is Right for You?
Choosing on price per litre alone can be misleading. The following questions will help you make the right decision:
- What type of work do you do? If you mainly carry out spot and panel repairs, MS clear coat is a practical, economical option. On full resprays and work where appearance comes first, HS clear coat makes the difference.
- Is your equipment suitable? Getting the most out of HS clear coat requires a spray gun that atomises well, sufficient air capacity and, ideally, a spray booth with baking capability.
- How valuable is your booth time? Fewer coats mean less time in the booth; in busy workshops, this can offset the higher price per litre of HS.
- Do you have environmental targets? If reducing solvent emissions is a priority, HS clear coat is the natural choice.
Tip: If you use both types of clear coat in the same workshop, pair the clear coat and hardener tins with coloured labels. A common mistake when work is hectic is adding HS hardener to MS clear coat, or vice versa.
To identify the right product combination for your type of work and substrate, use our Product Selector.
Summary
HS clear coat offers high film build in few coats, a deep appearance, a generous polishing margin and low solvent emissions, but in return it requires the right equipment and application discipline. MS clear coat, by contrast, is easy to apply and forgiving, and it is an economical solution for spot repairs. Whichever you choose, using the matching hardener and the ratios given in the TDS is a prerequisite for a lasting result.