Glass finishing: a brief overview

Glass finishing is a key element of modern glass processing. Over the past decades it has developed into a precise science allowing the properties of glass surfaces to be treated selectively.

The aesthetic and functional properties of glass can be optimised using a multitude of glass finishing processes.

• Aesthetics: Processes such as sandblasting, etching and printing serve to create individual and appealing surface textures.
• Functionality: Glass can be finished to be dirt-repellent, scratch-resistant, self-cleaning or anti-glare.
• Safety: Special coatings can increase the final strength of glass.
• Thermal, noise and UV protection: Finished glass can provide effective protection against heat and noise transmission and also against UV rays.

Mechanical processes

These are often the first step in glass finishing. Physical impact such as sandblasting, grinding and polishing serve to prepare the surface for downstream treatments and produce basic surface textures.

• Sandblasting: Sandblasting is probably the most frequently used mechanical finishing process used for glass. It is comparatively easy to carry out, low-cost and produces a multitude of surface textures ranging from frosted to rough. It is often applied for privacy glazing, frosted glass, for preparing surfaces for downstream treatments or for removing old coatings.
• Grinding and polishing: Alongside sandblasting, grinding and polishing are widely used methods. These processes produce smooth, shiny or frosted surfaces and are often used for high-quality products such as the production of optical components such as lenses or prisms as well as decorative elements.
• Engraving: Patterns or lettering are manually scratched into the glass by means of special tools. This method is highly precise but also very time-consuming.
• Ultrasonic treatment: Ultrasonic treatment is a special process used less frequently due to the high investment costs and increased technical expenditure. This process, however, is indispensable for specific applications due to its high precision and the possibility of producing very fine textures. It is primarily used for producing micro-optical components, in medical device technology and in electronics.

Chemical processes

Here the glass surface is changed by chemical reactions. In etching the glass surface is removed selectively resulting in relief-type textures. In coating a thin layer of another material is applied to the glass surface.

• Wet chemical etching: In this classic process the glass is dipped into an etching solution. As the glass reacts with the solution, material is removed and the surface textured. The etching rate and resulting surface profile can be precisely set by the choice of etching solution, its concentration and exposure.
• Deep etching: Here the depth of a texture is increased by masked etching. In this process the glass is coated with a light-sensitive layer that serves as masking after exposure and development. The non-exposed areas are removed by the etching solution while the exposed areas remain protected. Deep etching is for instance used for manufacturing micro-lenses or fibre optics.
• Plasma etching: A more modern process in which plasma composed of reactive gasses is shot at glass in a vacuum chamber. The energy-rich ions in the plasma remove the glass on atomic level. Plasma etching ensures very high precision and an anisotropic etching, i.e. the etching rate is markedly higher vertically than horizontally. This is of particular importance for the production of micro-electronic components and MEMS (micro-electro-mechanical systems).
• Coating (chemical): e.g. by vapour deposition or dipping.

Physical processes

Physical processes use heat, pressure or radiation to change glass properties.

• Tempering: In tempering glass is heated to and kept at a specific temperature to remove internal stresses. Subsequently, the glass is cooled off in a controlled manner to prevent new stresses from forming. This process improves the strength and durability of the glass by reducing the stresses that have formed during production or processing.
• Coating (physical): Coatings have greatly increased in importance over the past years. Thin layers of various materials (e.g. metals, oxides) are applied to the glass surface to afford it specific properties. The choice of coating material and process depends on the desired characteristics.
• Sol-gel process: Here a colloidal solution (sol) is applied to the glass and forms a three-dimensional network (gel) by controlled drying and heating. This method makes it possible to produce porous or dense layers of high purity.
• Sputtering: In this process atoms or molecules of a target material are removed by ions and deposited on a glass substrate. Sputtering makes it possible to produce very thin and homogeneous layers.
• Chemical vapour deposition (CVD): Here gaseous precursor materials react at the hot glass surface forming a solid layer. CVD provides high precision and permits the production of complex layered textures.
• Lasering: Laser beams can melt fine textures or lettering into the glass selectively.

Architecture

• Energy-saving building skins: Low-E coatings reduce heat losses in winter and prevent overheating in summer.
• Self-cleaning facades: Hydrophobic and photocatalytic coatings make for effective self-cleaning.
• Safety glass: Coated glass provides better burglary protection and prevents injuries.
• Design and aesthetics: Individually designed glass surfaces contribute to designing unique buildings.

Electronics

• Smartphones and tablets: Finished glass is used for their displays to make them scratch-resistant, anti-fingerprint and glare-free.
• TV sets: Special coatings improve contrast and colour rendition.
• Computer monitors: Anti-glare coatings reduce irritating reflections.

Automotive

• Windscreens: Coatings protect against UV radiation and improve vision at night.
• Side windows: Tinting and coatings increase privacy and reduce interior overheating.
• Rear mirror: Heatable coatings prevent misting in humid air.

Furniture

• Tables and shelving: Finished glass gives furniture a modern look and is easy to clean.
• Kitchen tabletops: Scratch and heat-resistant glass is hygienic and durable.
• Shower cubicles: Water-repellent coatings ease cleaning.

Art

• Sculptures: Glass artists use various finishing methods to create unique and aesthetic artworks.
• Paintings: Glass can serve as a substrate for paintings and make for special effects.

• Schaeffer, H. A.; Langfeld, R. (2014): Werkstoff Glas - Alter Werkstoff mit großer Zukunft. Springer Vieweg, Berlin, Heidelberg.
• Theuerjahr, R. (2022). Die Glasologie: Das Fachbuch für Glas (2. Aufl.). Theuerjahr.