Applications and Benefits of Laser Marking on Glass
Glass is a naturally occurring material composed mainly of silica (SiO2). It is an amorphous solid, and therefore its atoms are rigid as in a crystal but disordered as in a liquid and therefore, are likened to subcooled liquids of very high viscosity.
Most commercially available glass is not only composed of silica; other compounds are added to this material that modify the properties of the glass and make it suitable for different uses. However, the addition of substances to the composition changes the “laserability” of the material.
Industrial glass has a more uniform structure and therefore lends itself better to laser processing. Handcrafted glass, on the other hand, lends itself less to laser processing. In this case, the very craftsmanship may result in inconsistencies in composition and structure such as microcracks that, when subjected to the heat generated by the laser, could break the glass.
Transparency, compactness and structural homogeneity, total chemical and biological inertness, impermeability to liquids, gases, vapors and microorganisms, inalterability over time, sterilizability and perfect ecological compatibility thanks to the possibility of recycling an infinite number of times. These are the outstanding intrinsic characteristics of glass, which is made entirely of natural substances.
Characteristic of glass is its poor tolerance of thermal expansion. When glass is subjected to laser, fractures are produced at the microscopic level, resulting in marking or cutting.
Depending on the type of glass, the marking process can take place in different ways.
- Sodium-calcic glass:
Soda-lime glass is the most common type of glass. Used the production of windows, bottles, glass tableware and other everyday objects, it lends itself well to laser processing.
On this type of glass, marking is achieved through the generation of thousands of micro-fractures on the surface of the glass. Thermal shock causes expansion of the glass, which, being a rigid material, fractures. This results in an opaque mark with a satin appearance, quite similar to the workings performed by traditional methods but at a much lower cost.
Some examples of applications are to be found in the decoration industry (decoration of glass glasses and tableware, window glass, and interior glass in general), the automotive industry (engraving of identification codes on automobile glass), and laboratory glassware production (engraving of graduated scales).
- Quartz glass
Quartz glass is obtained by fusing quartz instead of silica. Its characteristics are high temperature resistance, excellent optical transmissibility and high corrosion resistance.
The processing of quartz glass byCO2 laser is done by surface fusion. Fusing the material changes the lattice structure of the glass, changing the refraction of light relative to the rest of the surface, resulting in a recognizable sign.
- Boron-silicate glass
Borosilicate glass, also known by the trade name Pyrex, is made by adding minerals such as boron along with other compounds to silica. The resulting chemical reaction produces a glass with excellent resistance to thermal expansion. For this reason it is widely used in the production of tableware and baked goods. Borosilicate glass can be subjected to marking byCO2 laser.
Advantages of laser on glass over other technologies:
Laser glass etching is an extremely efficient process that has proven to be economically viable for both small production runs and mass production.
Such an engraving:
- is resistant to wear and tear as well as corrosion and contact with aggressive substances, such as concentrated detergents or acids.
- Costs are low because there are no consumables (sprays, ink, pastes, etc.).
- Speed, even in format changes: you can mark different products without downtime.
- High definition, even for very small markings.
Compared to a process such as Sandblasting on glass or Mechanical Engraving:
- Laser engraving has no design limitations: sandblasting is less precise than laser engraving and cannot create fine details.
- It is a faster process: Sandblasting takes longer than laser engraving.
Types of lasers: UV, CO2 and Picosecond
The interaction between lasers and glass is affected by laser wavelength and pulse duration. Picosecond lasers are ideal for high-precision applications.
Picosecond Laser and Glass
Picosecond lasers generate extremely short laser pulses, with pulse durations on the order of picoseconds. They are characterized by a wavelength of 1030 nm and spot circularity over 96%. Each pulse has cica duration of 1.9 ps and maximum energy of 26.4 μJ. In burst mode, it can deliver very high energy pulses (over 230-250 μJ at 200kHz)
When these pulses hit the glass, the concentrated energy in such a short period of time creates a very intense interaction with the material.
The laser energy is sufficient to break chemical bonds in the glass, creating small cavities or incisions.
Unlike longer wavelength lasers, picosecond lasers generate minimal heating of the surrounding material because the energy is concentrated in a short time instant. This reduces the risk of thermal damage to glass, making picosecond lasers ideal for marking and precision machining applications.
CO2 Laser and Glass
CO2 lasers emit radiation at a wavelength of 10600 nanometers and a circularity of more than 90%, which is in the far-infrared region. When this radiation hits the glass, it is absorbed by the material, causing the surface to heat up.
The interaction between theCO2 laser and glass can result in:
Melting and Ablation: Due to heating, glass may melt or ablate from the surface. This makesCO2 lasers suitable for cutting and etching glass, but may be less precise than picosecond lasers in terms of processing details.
Increased heat propagation: CO2 lasers generate more heat propagation in the material than picosecond lasers, which can increase the risk of creating unwanted fractures or thermal damage to the glass.
UV Laser and Glass
UV lasers operate at much shorter wavelengths, typically between 100 and 400 nm, circularity over 98 percent. When this radiation hits the glass, it can cause photoablation phenomena, similar to picosecond lasers, but on a coarser scale.
Experimental tests comparing UV, PICO and CO2
The tests were carried out by going to mark on a traditional glass the same design (Lasit Logo) with the optimal marking parameters for each optical system/source.
The types of sources used are: CO2, UV and Fiber (Pico with burst mode).
The measurements made and the images captured, were obtained with the use of a panfocal microscope: 4k Microscope – VHX Series 7000, which allows visualization of the three-dimensional profile of the marking with zoom levels ranging from a minimum of 20x to a maximum of 2500x.
CO2 – Surface Marking
Description of experimental results CO2
In the case of the CO2 source, a marking characterized in general by low definition and high roughness (Ra=6um and Rz=24um) is obtained.
In particular, it is observed that the details of smaller features are barely visible, so this type of source is not recommended for making markings having small and minute details.
This result is caused by a larger laser spot size and the grain size on the machined surface having large grains (of about 11500 um2).
In addition, precisely because of the large spot and grain sizes, it is not possible to make markings inside the material.
However, this type of marking has the advantage of presenting: wide working range and depth of field and reduced marking time.
| Properties | Result (1 is worst, 3 is best) |
| Definition of marking | ☆ |
| Surface finish | ☆ |
| Laser spot size | ☆ |
| Grain size | ☆ |
| Depth of field | ☆ ☆ ☆ |
| Size of Marking Plane | ☆ ☆ ☆ |
| Marking Time | ☆ ☆ ☆ |
| White marking inside the material | NO |
| Dark marking inside the material | NO |
UV – Surface Marking
Internal marking
Description of UV experimental results
In the case of the UV source, marking characterized in general by good definition and high roughness (Ra=6um and Rz=26um) is obtained.
In particular, it is observed that the details of smaller section sizes are clearly visible, so this type of source can be used for making markings having small and minute details.
This result is made possible by a smaller laser spot size and the uniformity of the grain size present on the processed surface. Since the reactivity of the material is high with this type of the source, a greater depth of the marked profile is generally observed (in tests up to 66um). In addition, with this type of source it is possible to make markings inside the material, which turn out to be well-defined and uniform. In addition, this type of marking has the advantage of presenting: wide working range and depth of field.
| Properties | Result (1 is worst, 3 is best) |
| Definition of marking | ☆☆ |
| Surface finish | ☆ |
| Laser spot size | ☆ |
| Grain size | ☆☆ |
| Depth of field | ☆ ☆ ☆ |
| Size of Marking Plane | ☆ ☆ ☆ |
| Marking Time | ☆ ☆ |
| White marking inside the material | ☆ ☆ |
| Dark marking inside the material | NO |
UV laser marking on glass: quality, precision and productivity for the promotional sector
In the world of promotional items and personalized gifts, glass has always represented a prestigious material. Glasses, bottles, trophies, commemorative plaques and gift items require workmanship that respects the elegance of the medium and ensures long-lasting results. UV laser marking on glass has established itself as the most effective technology for achieving superior engravings on glass, capable of combining impeccable aesthetics and high productivity.
White marking on glass, achieved by UV laser, is distinguished by its high contrast and elegant appearance. The end result is a smooth, uniform and durable surface that does not degrade even after repeated washing or exposure to the elements. For a company operating in the promotional sector, this translates into finished products that keep their perceived value intact and communicate professionalism to the end customer.
PICO – Surface Marking
Description of experimental results PICO BURST
In the case of the Fiber source with picosecond pulses, marking characterized in general by high definition and low roughness (Ra=2um and Rz=12um) is obtained.
In particular, it is observed that the details of smaller strokes are excellently visible, so this type of source is recommended for making markings having small and minute details.
This result is made possible by a low laser spot size, low contact time with the material and the uniformity of the grain size present on the machined surface, the size of which is around 60 um2.
Since the pulse is on the order of picoseconds, all the energy is used to machine the surface, limiting heat dissipation within the material. For this reason, the profile depth is shallow (10um), being limited to the machined surface.
In addition, thanks to the bust feature with which this type of source is equipped, it is possible to make markings inside the material in two color shades (light and dark), which turn out to be well-defined and uniform in both cases.
In addition, the marking type has the disadvantage of having reduced working range and depth of field.
| Properties | Result (1 is worst, 3 is best) |
| Definition of marking | ☆ ☆ ☆ |
| Surface finish | ☆ ☆ ☆ |
| Laser spot size | ☆ ☆ ☆ |
| Grain size | ☆ ☆ ☆ |
| Depth of field | ☆ |
| Size of Marking Plane | ☆ |
| Marking Time | ☆ ☆ |
| White marking inside the material | ☆ ☆ ☆ |
| Dark marking inside the material | ☆ ☆ ☆ |
Comparison results
| Properties | CO2 results | UV results | PICO result |
| Quality of marking | ☆ | ☆☆ | ☆ ☆ ☆ |
| Surface finish | ☆ | ☆ | ☆ ☆ ☆ |
| Spot size | ☆ | ☆ ☆ | ☆ ☆ ☆ |
| Grain size | ☆ | ☆ ☆ | ☆ ☆ ☆ |
| Depth of field | ☆ ☆ | ☆ ☆ ☆ | ☆ |
| Size of Marking Plane | ☆ ☆ | ☆ ☆ ☆ | ☆ |
| Marking Time | ☆ ☆ ☆ | ☆ ☆ | ☆ ☆ |
| White marking inside the material | NO | ☆ ☆ | ☆ ☆ ☆ |
| Dark marking inside the material | NO | NO | ☆ ☆ ☆ |