Inside the Furnace – How Glass Melting Happens at 1670°C — Where Raw Powder Becomes Medical-Grade Glass

Inside the Furnace – How Glass Melting Happens at 1670°C

— Where Raw Powder Becomes Medical-Grade Glass

At SCHOTT, glass for injectable devices isn’t just melted — it’s engineered through precise thermal, atmospheric, and chemical control. The result is ultra-pure, bubble-free borosilicate glass, trusted by pharmaceutical manufacturers worldwide.

A 3-Zone Furnace, Built for Precision

The melting process begins in an end-fired regenerative furnace, enhanced by oxy-fuel boosting for consistent high temperature and clean combustion.

Critical temperature control zones include:

• Melting zone: 1670 ± 20°C

• Refining zone: 1570 ± 15°C

• Working end: 1370 ± 10°C

An integrated λ-probe system continuously monitors the oxygen atmosphere, ensuring chemical balance for complete melt homogenization.

Refining for Clarity – Eliminating Bubbles & Stones

SCHOTT uses:

• Argon bubbling (99.999% purity) to release entrapped gases

• Na₂SO₄ fining agent (0.2–0.5%) to remove seed bubbles

• Optical transmission inspection, ensuring <0.1 bubbles/cm²

These steps ensure optical clarity and eliminate internal flaws, even at micro levels.

Real-Time Monitoring and Quality Control

• Furnace cameras observe melt flow and color

• Daily melt samples are extracted and analyzed

• Temperature drifts are corrected with PID-controlled feedback

This digital control loop ensures dimensional consistency in every tube drawn from the melt.

✅ Key Takeaways

• SCHOTT melts borosilicate glass at 1670°C in a 3-zone controlled furnace

• Argon bubbling and sulfate fining eliminate bubbles and inclusions

• λ-probes and furnace cameras maintain real-time melt integrity

• Optical purity is verified before forming begins

Want to see how melt precision drives product quality?
Contact us to learn more about SCHOTT glass syringe OEM production.

#SCHOTTGlass #BorosilicateGlass #GlassMelting #InjectionDevice #MedicalGlass #PrefilledSyringe #OEMManufacturing