Laser Marking of Glass – How to Avoid Cracks

# Laser Marking of Glass — How to Avoid Cracks?

Glass is a transparent, brittle material. The biggest challenge in laser marking glass is the thermal stress that leads to cracks and shattering. However, with the right approach, laser can produce beautiful, permanent marks on glass.

**Laser Types Suitable for Glass Marking:**

**CO2 Laser (10.6μm) — The Preferred Solution**
Glass has extremely high absorption of 10.6μm CO2 laser. The laser energy is absorbed directly on the surface, with the heat-affected zone concentrated on the surface layer. With proper parameter control, crack-free marking can be achieved.

**UV Laser (355nm) — The Precision Solution**
UV laser photons have high energy, directly breaking molecular bonds (cold processing) with minimal thermal effects, making it ideal for ultra-fine marking.

**Fiber Laser (1064nm) — Not Suitable**
Glass is essentially transparent to 1064nm infrared laser, unable to absorb it effectively, resulting in very poor marking results.

**Key Techniques for Glass Marking:**

1. **Control Power Density**: Excessive power can cause thermal shock and cracks. Start with low power and adjust gradually
2. **Pulse Width Control**: Short pulses reduce heat accumulation and lower thermal stress
3. **Proper Defocusing**: Slight defocusing can disperse energy density and avoid localized overheating
4. **Preheating Assistance**: For thick or fragile glass, appropriate preheating can reduce temperature gradients
5. **Marking Method**: Dot-matrix marking is safer than continuous scribing, as heat is more dispersed

**Application Scenarios:**
– Custom logo marking on glassware
– QR code marking on glass panels
– Laboratory glassware numbering
– Decorative marking on architectural glass

**Summary:** For glass marking, use CO2 laser or UV laser. The key is to control heat input and avoid stress concentration. Parameter tuning is critical — start low rather than high.