The Quartz Glass Manufacturing Process, Step by Step

Fused silica production follows nine main stages: raw material selection, fusion, forming, CNC machining, flame working, fire polishing, annealing, precision cleaning and quality inspection. Each stage protects purity and dimensional accuracy. Quartz glass melts above 1700°C, so the process demands precise temperature control and clean handling throughout.

Purity verified by ICP-MS at the raw-material and final-inspection stages.

Quartz is melted by electric arc, flame, plasma or synthetic CVD methods.

From raw quartz sand to a finished, inspected fused silica component.

Step 1 — Raw Material Selection

The process begins with raw material. We select high purity quartz sand or synthetic silica precursors with SiO₂ above 99.99% and sub-ppm metallic impurities. Natural quartz sand suits most industrial and semiconductor work. Synthetic silica, made from a silicon precursor, is used when the lowest metal content and best deep-UV transmission are required. As a result, the grade of the finished fused silica is set at this first stage.

Step 2 — Fusion (Melting)

Next, the raw material is melted into fused silica above 1700°C. There are four main quartz fusion methods. Electric arc fusion uses a graphite electrode and is common for tubes and large blocks. Oxy-hydrogen flame fusion gives clearer, lower-bubble glass. Plasma fusion reaches very high purity for optical grades. Synthetic CVD deposition builds ultra-pure silica directly from a vapour precursor. The chosen method controls bubble content, OH level and optical clarity.

Step 3 — Forming

After fusion, the soft glass is formed to shape. Tubes and rod are drawn continuously to target diameter and wall thickness. Plate is cast or sliced and ground flat. Crucibles are shaped by rotational moulding or pressing. Throughout, temperature and pulling speed are controlled to hold geometry and concentricity.

Step 4 — CNC Machining

Formed quartz is then machined to final dimensions. CNC grinding, cutting and drilling produce tight tolerances and clean edges. This stage delivers the precise diameters, lengths and slot spacing needed for semiconductor and optical parts. Diamond tooling is used because quartz is hard and brittle.

Step 5 — Flame Working & Fabrication

For complex parts, oxy-hydrogen flame working joins, bends and shapes the glass. Skilled glassblowers add ports, flanges, bends and end caps. This is how multi-port reactors, sealed assemblies and custom quartz components are built. Flame working also repairs and modifies standard stock into bespoke designs.

Step 6 — Fire Polishing & Surface Finishing

Surfaces are then finished. Fire polishing melts the outer layer slightly to remove tool marks and create a smooth, clear surface. For optics, mechanical and chemical polishing achieve high flatness and low surface roughness. Good surface finish improves transparency, laser-damage resistance and cleanliness.

Step 7 — Annealing

Annealing relieves internal stress. The part is reheated and then cooled slowly through the annealing point near 1215°C. This prevents cracking and reduces birefringence in optical components. Therefore, annealing is essential for parts that face thermal cycling or precision optical use.

Step 8 — Precision Cleaning

Before delivery, components are cleaned. Acid etching and ultrasonic cleaning remove surface metals, dust and handling residue. Clean surfaces lower the risk of devitrification at high temperature and prevent contamination in semiconductor and laboratory use.

Step 9 — Quality Inspection

Finally, every part is inspected. We verify purity by ICP-MS analysis and dimensions by CMM. We also check for bubbles, inclusions, striae and surface defects. Each order ships with test data and full traceability, so performance stays consistent batch to batch.

The fusion method sets the purity, clarity and OH content of the finished glass. Here is how the four main quartz fusion methods differ.

Melts natural quartz sand with a graphite electrode. It is efficient and well suited to tubes, rod and large blocks. The glass is strong, but it may contain some bubbles.

Uses an oxy-hydrogen flame to melt the material. It produces clearer, lower-bubble glass with higher OH content. Therefore, it suits transparent tubing and general optical work.

Melts quartz in a plasma flame with very low contamination. It produces low-OH, high-purity glass. As a result, it is used for demanding UV and laser optics.

Builds silica directly from a vapour precursor. It gives the highest purity and best deep-UV transmission. Consequently, it is the choice for excimer-laser and semiconductor optics.

The same fused silica production process yields different grades, depending on the fusion method and OH level. JGS1 is synthetic high-OH fused silica with excellent deep-UV transmission below 250 nm, ideal for UV and laser optics. JGS2 is high-purity natural fused silica for visible and near-IR optics and for low-contamination semiconductor and solar parts. JGS3 is low-OH infrared-grade silica for near-IR transmission. We also produce clear and opaque grades: clear glass transmits infrared for heating and pyrometry, while opaque glass scatters infrared for thermal insulation and shielding.

This manufacturing process produces our full range of quartz glass: tubes, rod, plate, crucibles, semiconductor boats and custom quartz glass. These parts serve six industries — see our quartz glass applications. To learn more about our facility and history, visit the About FGQuartz page.

From fusion to final inspection, FGQuartz controls every step of the quartz glass manufacturing process in-house. Send us your drawing or requirements, and our engineering team will recommend the right grade, method and finish — with no minimum order on custom parts.