What do you mean by good glass?

What Makes "Good Glass" – The Invisible Excellence

1. Tranquility, a Continuous Entirety

Flawless Texture: A close look under the light reveals no bubbles or grit. Inferior glass is like a flower in the fog; good glass is like a deep, still pool of water.
Clean Cut: The edges are polished to the smoothness of a pebble, free of burrs or scratches. The craftsman repeatedly rubs them with his fingertips to ensure a smooth finish.

2. A Strong and Calm Body

Unfazed by Changes: Hot soup can be poured into it in the cold winter without shattering. This material was once used in traditional medicine bottles (in the jargon "resistant to sudden changes in temperature").
Fire Marks: Borosilicate glass emits a faint blue flame during firing. While ordinary glass can only withstand temperature fluctuations of 50°C, this glass can withstand drastic changes of 200°C.

3. A Century of Transparency

Anti-Aging: Added rare earth elements (such as cerium) protect against the erosion of sunlight and ultraviolet rays. Museum display cases remain yellowing for a century.
Refined as New: Washed through the dishwasher thousands of times, it remains as clear as new. Low-quality glass becomes hazy and frosted after three years.

4. Silent Guardian

Food-Safe: Zero leaching of heavy metals (especially lead and cadmium). Antique European crystal cups are magnificent but contain lead, making them unsuitable for storing wine.
Inert Fortress: No sodium seeps into vinegar, and no odor remains in wine. Medical ampoule bottles are examples of this type of glass.

5. The Warmth of Handcrafting

Blowing Marks: Top-quality handmade cups intentionally retain subtle swirls, a testament to the meticulous craftsman's meticulous shaping.
Mold Craftsmanship: Industrially mass-produced glass has noticeable seams, while fine cracks in glass molded with a good mold require a magnifying glass to detect.

6. Elegance in Shattering

Tempered Glass: When shattered by force majeure, mobile phone screen glass shatters like snowflakes, while architectural glass falls into a spider web without scattering.
Dignity in Death: No explosive, injurious spray.