A few months ago, we launched a discussion on Etalon LinkedIn group, which was about automotive clearcoats’ classification. The problem is that there is no clear distinction between MS, HS and Ultra HS clearcoats. In fact, most of the suppliers prefer to name its clears HS, even if the product is low in solids. Wouldn’t it be better to have some official classification in place? Many colleagues sent their suggestions and comments; therefore, I would like to summarize the discussion in the following blog post.
As automotive refinish materials supplier, I see a lot of confusion concerning clearcoats commercial names. One could see ibn the market a low quality clears named HS or VHS, causing many misunderstanding and false expectations. Below you can find five opinions on how to classify clearcoats according to their quality, properties and composition.
- By solvent content.
All the clearcoats used today in car refinishing industry, employ organic solvents. Even if water based clears appear here and there, but they still have not reached comparable results to the conventional solvent clears, both for application and final appearance. Three different categories of clears with progressive reduction of solvent content are presented below:
- MS (medium solids) – the resin particles are larger compared to HS or UHS clearcoats. The amount of thinner necessary to obtain the right application viscosity must be about 20% greater than the other types (usually VOC 550-580 g/l)
- HS (high solids) – the resin particles are smaller compared to the MS ones, and the amount of solvent is around 15% (usually around 420 g/l).
- UHS or VHS (ultra or very high solids) – the size of resin particles is even smaller and consequently it is possible to reduce by thinner up to 10% (less solvents than 420g/l).
- By solids content.
Not all the producers actually include this information on their labels. Solids content is measured in percentage by either weight or volume.
- MS (medium solids) – solids content 40-45%
- HS (high solids) – solids content 45-50%
- UHS or VHS (ultra or very high solids) – 50% and higher
- By VOC compliance
Since 2004 EU Directive for Volatile Organic Compounds (VOC) in Paints, Varnishes and Vehicle Refinishing Products limits VOC content in topcoats, including clearcoats, up to 420 g/l. Taking this figure as starting point, many professionals regard all non-compliant clearcoats as MS (medium solids), while clears with VOC less or equal to 420 g/l as HS or UHS.
- By number of coatings
Some vehicle refinishing professionals judge clearcoat on the number of layers you need to achieve appropriate film thickness. Simplistic categorization of clearcoats according to the number of coats applied looks as following:
- MS (medium solids) – 2 or 3 coats
- HS (high solids) – 2 coats
- UHS or VHS (ultra or very high solids) – 1 or 1 full and a 1 mist coats
- By feeling
As my colleague, Malcolm Cutting mentioned in his post, some painters will even describe the difference between HS and MS as one is thicker and you can really lay it on, while the other is runny, rather liquid.
To summarize, I believe that automotive paint suppliers should be careful with giving misleading commercial names to their products. Of course, some kind of standard accepted across the industry would really help to end the confusion.
Special thanks to my colleagues, who participated in this discussion and especially to Hamid Elhalfi, Gregory Boccardo, Marc Toegaert, Rob Dumais, Mike Fahham, Malcolm Cutting, Lori Lorenz, Carmelo DiLuciano, Jack Reinking.