Glass coatings: special factor geometry
Glass coatings do not enjoy the greatest attention in the coatings industry. They are omnipresent and technically highly exciting. An interview with Swarovski shows how cut crystal glass is coated and where standard coatings reach their limits.
Which properties are currently most important for glass coatings at Swarovski?
To answer this question, you have to differentiate between a decorative or functional coating. Depending on that, different properties are prioritised. The common factor is chemical and mechanical resistance. For example, Swarovski crystals are often used for jewellery pieces. Therefore, they are usually in direct contact with the skin of the jewellery wearer. Due to this, Swarovski crystals must be resistant to exposures as sweat but also environmental factors such as UV radiation, sea or chlorine water.
What are the particular challenges of coating compared to other glass substrates for Swarovski?
The special challenges for the coating of Swarovski crystals are that they are exposed to the mentioned stresses without further protection. In addition, their geometry is also a special factor. The cut gives Swarovski crystals their shape, countless facets and thus their brilliance. The combination of flat surfaces and edges at different angles is a great challenge for coatings. Especially with sharp edges, the requirements go far beyond those of standard applications such as e.g. for furniture, door handles or even cars.
In automotive painting, layers have a typical thickness of 50 -70 microns. If a coating with this thickness is pulled over an edge of a crystal, the original edge radius and thereby the brilliance is lost. The coating would consequently reduce or even eliminate the desired property of the product. Another aspect is the size of Swarovski crystals. The portfolio also includes products that are less than 1 mm in size. Smaller products are often coated simultaneously in a larger quantity. For these products also, a consistent result must be achieved in order to meet the set quality standards.
And how do you apply the coating to these small crystals?
A coating process in which the Swarovski crystals rotate is not a feasible solution. Based on many years of expertise and in-house know-how, a special and proprietary technology has been developed by positioning the crystals in a way that the various geometries are evenly coated.
In which situations do you refer to organic or inorganic coatings?
This question is rather subordinated to the coating for Swarovski crystals. First and foremost, it is about how the desired layer thickness can be realised. For a protective layer which is intended to provide a barrier to chemical stresses such as sweat or seawater, organic coatings are often preferred.
These allow the required layer thickness. Inorganic coatings are more likely to be used if the geometry of the product is more important and the visual impact of the Swarovski crystal is not to be reduced. In these cases, vacuum processes are preferred in order to achieve a uniform coating.
Can you give a brief outlook on future trends that are important for glass coatings?
The individual client expectations and wishes are becoming more and more important. In addition to customisation, the demand for smaller and more variable lot sizes is also increasing. An increasing trend is also the desire for additional functions, such as electronic touch functions.
These go far beyond a decorative or protective coating function. Coatings are not intended to interfere with these additional functions, but rather to enable or even enhance them. Examples include light switches or panels that use “smart” Swarovski crystals.
The interview was conducted by Jan Gesthuizen
Event tip
Klaus Monz, Head of Coating Development at Swarovski, gives more detailed information on the coating of crystal glass and touch surfaces in a keynote speech at the European Coatings Glass Forum, which takes place on 17 – 18 June in Berlin.
