## Common ground
All options are types of crystallising dishes, used for growing or holding crystals in laboratory or industrial settings.
## Options at a glance
**3926.90 – Plastic**
- **Defining trait:** Made from plastic, offering lightweight, impact-resistant, and low-cost properties.
- **Typical examples:** Polyethylene or polystyrene crystallising dishes.
- **Best fit when:** Durability, low weight, or cost-effectiveness are priorities; not for high heat or corrosive chemicals.
**6903 – Refractory ceramic**
- **Defining trait:** Designed to withstand very high temperatures and thermal shock.
- **Typical examples:** Dishes made from alumina or silica-based ceramics.
- **Best fit when:** Used in high-temperature processes like crystal growth from molten solutions.
**6909.1X – Ceramic**
- **Defining trait:** General ceramic material, typically non-refractory, with moderate heat and chemical resistance.
- **Typical examples:** Porcelain or stoneware crystallising dishes.
- **Best fit when:** Moderate temperature use and chemical stability needed; common in standard lab settings.
**7017 – Glass**
- **Defining trait:** Transparent, chemically inert, and heat-resistant (but not shock-resistant).
- **Typical examples:** Borosilicate or soda-lime glass dishes.
- **Best fit when:** Visibility of crystal formation is essential, or for handling corrosive solutions.
## Key differences
| Feature | Plastic | Refractory Ceramic | Ceramic | Glass |
|---------------------|-------------|--------------------|---------------|---------------|
| Heat resistance | Low | Very high | Moderate | High (but not shock-resistant) |
| Chemical resistance | Variable | High | Good | Excellent |
| Transparency | Opaque/Translucent | Opaque | Opaque | Transparent |
| Fragility | Low | Low | Medium | High |
## How to choose
- Is the dish used at high temperatures (>500°C)? → 6903
- Does it need to be transparent for observation? → 7017
- Is cost and durability most important? → 3926.90
- Is moderate heat and chemical resistance sufficient? → 6909.1X
## Overlaps & pitfalls
- Glass (7017) and ceramic (6909.1X) may both be used in labs; choose glass for visibility, ceramic for general use.
- Refractory ceramic (6903) is a subset of ceramic but defined by extreme heat resistance—do not confuse with standard ceramics.
- Plastic may be mistaken for low-cost alternatives, but it fails under heat or strong solvents.
- No clear priority: choose based on the **main function**—e.g., visibility vs. temperature vs. cost