If you hold two pieces of quartz glass side by side, you cannot tell them apart.
Same color. Same clarity. Same chemical formula: SiO₂.
But shine a 193nm deep-UV laser through one of them, and it passes straight through. Shine the same laser through the other, and it's completely absorbed before it even reaches the other side.
This isn't a defect. Both pieces are exactly what they're supposed to be. They just belong to different grades — made from different raw materials, using different processes, to completely different purity standards.
That single word — purity — is what separates one type of quartz glass from another. And understanding it is the difference between specifying the right material and paying twice for the same part.

Why Are There Different Types of Quartz Glass?

Because the raw material isn't always the same — and neither is the process used to melt it.
Quartz glass is silicon dioxide (SiO₂) in its purest amorphous form. But "pure" is relative. Natural quartz crystals contain trace metals, hydroxyl groups (OH), and other impurities that behave very differently depending on your application. A grade that works fine for a furnace tube becomes completely unsuitable the moment you need UV transmission below 200nm.
The short version: purity level and manufacturing method determine everything — optical performance, thermal stability, and price.

Why Purity Changes Optical Performance

This is the part most buyers skip — and then wonder why their transmission data doesn't match the spec sheet.
Two impurities matter most:

Hydroxyl content (OH). High-OH quartz transmits well in the UV range (below 250nm) but absorbs infrared around 2.7μm. Low-OH quartz does the opposite — good IR transmission, weaker deep-UV performance. If your application sits in the mid-IR range (2–4μm), high OH content will actively hurt you.

Metallic impurities. Even a few parts per million of iron, aluminum, or titanium creates absorption bands that shift where your material transmits and where it doesn't. In standard industrial applications, this rarely matters. In UV laser optics or fluorescence-based instruments, it's the difference between a working component and a useless one.
The cleaner the glass, the wider the usable wavelength window — and the higher the price. You're not paying for a brand name. You're paying for the absence of things that would otherwise interfere with your application.

Industrial Quartz Glass Grades: JGS1, JGS2, JGS3

China's national standard divides optical-grade quartz glass into three grades. These are the designations you'll encounter most often when sourcing quartz glass for industrial or optical use.
JGS1 is produced from synthetic fused silica and typically contains relatively high hydroxyl (OH) content, often in the hundreds of ppm range. and minimal metallic impurities. The transmission window runs from approximately 185nm in the deep UV all the way through to 2500nm in the near-infrared. This is the grade used in UV optics, excimer laser components, semiconductor equipment windows, and precision spectroscopy instruments. It costs more, and it's worth it when UV performance is non-negotiable.
JGS2 is the mid-range grade — and the most widely used. It's made from high-purity natural quartz with moderate OH content. Transmission starts around 220nm in the UV and extends to roughly 2500nm. It won't give you the deep-UV performance of JGS1, but it handles most optical and laboratory applications well: sight glasses, furnace observation windows, general-purpose optical windows, and UV lamp envelopes. The price-to-performance ratio here is usually the best fit for buyers who don't specifically need sub-200nm transmission.
JGS3 is the thermal-grade option. Lower purity, higher OH content, and a narrower useful transmission range — but it's built for applications where optical transparency matters far less than thermal resistance and mechanical durability. Think high-temperature furnace tubes, semiconductor diffusion tubes, and industrial heating equipment. If you're putting quartz glass into a 1200°C environment and you don't care what wavelength it transmits, JGS3 is the right call at the right price.

How to Choose the Right Quartz Glass

Start with your application, not the grade.
Ask yourself three questions:

What wavelength range do you actually need?

 If your process involves UV light below 220nm, only JGS1 will consistently perform. If you're working in the visible range or near-IR, JGS2 covers you. If light transmission isn't the point, JGS3 is sufficient.

What's your operating temperature?

 All three grades handle high heat well — quartz glass softens around 1665°C and has a very low thermal expansion coefficient (0.55 × 10⁻⁶/°C). But surface contamination from metallic impurities in lower-grade material can cause localized failure under repeated thermal cycling at extreme temperatures.

How tight are your dimensional and surface tolerances?

 Higher-grade material is easier to polish to tighter surface quality specs (scratch-dig, flatness, parallelism). If your downstream process involves precision optical assembly, the additional cost of JGS1 often saves rework time later.
If you're still unsure, start with JGS2. It covers the majority of industrial and optical applications, and upgrading to JGS1 later — once you've validated your process — is simpler than over-specifying from day one.