## Common ground
All are laboratory crucibles used for heating, melting, or analyzing materials at high temperatures.
## Options at a glance
**3926.90 – Plastic**
- **Defining trait:** Made from plastic, unsuitable for high-temperature use.
- **Typical examples:** Disposable plastic crucibles for low-temp sample prep.
- **Best fit when:** Handling non-heat-sensitive samples or single-use applications.
**6903 – Refractory ceramic**
- **Defining trait:** Made from ceramic materials designed to withstand extreme heat and thermal shock.
- **Typical examples:** Alumina or zirconia crucibles for high-temp combustion analysis.
- **Best fit when:** Used in furnace environments above 1000°C.
**6909.1X – Ceramic**
- **Defining trait:** General ceramic construction; may include non-refractory types, less heat-resistant than refractory ceramics.
- **Typical examples:** Standard ceramic crucibles for moderate heating (e.g., drying).
- **Best fit when:** Moderate temperature use or general lab handling, not high-heat applications.
**7017 – Glass**
- **Defining trait:** Made from borosilicate or similar glass; heat-resistant but limited to lower temperatures than ceramics.
- **Typical examples:** Glass crucibles for titration or low-temp melting.
- **Best fit when:** Need transparency, chemical resistance, or use below 500°C.
## Key differences
| Option | Material Type | Max Temp (approx.) | Thermal Shock Resistance | Transparency |
|--------------|-------------------|--------------------|----------------------------|--------------|
| 3926.90 | Plastic | <100°C | Very low | Yes (if clear) |
| 6903 | Refractory ceramic| >1500°C | High | No |
| 6909.1X | Ceramic | ~800–1000°C | Medium | No |
| 7017 | Glass | ~500°C | Low | Yes |
## How to choose
- Does it need to withstand temperatures above 1000°C? → 6903
- Is it used for high-heat reactions like combustion or melting metals? → 6903
- Is transparency needed for visual monitoring? → 7017
- Is it intended for single-use or low-temp handling? → 3926.90
- Is it used at moderate heat (e.g., drying, evaporation)? → 6909.1X
## Overlaps & pitfalls
- **6903 vs. 6909.1X:** Both ceramic; refractory ceramic (6903) is a subset of ceramic. If the product is heat-resistant beyond standard ceramic, use 6903.
- **7017 vs. 6909.1X:** Glass and ceramic can both be used for moderate heating—choose based on transparency needs.
- **Vague label:** "Ceramic" (6909.1X) is broad; clarify if refractory properties are present.
- **Priority rule:** Use the product’s MAIN function and highest operating temperature to decide