7. Annealing & Thermal Stability
Annealing: Products must be annealed for approximately 8 hours (minimum 6 hours) after demolding to ensure long-term stability and prevent spontaneous cracking.
Thermal Shock Resistance: Glass containers must withstand a temperature difference of up to 39°C without breakage when transferred from hot water to cold water.
8. Surface & Mold Finish
Texture: No obvious water ripples allowed.
Imperfections: The surface must be smooth to the touch. Strictly prohibited are visible wrinkles, scratches, grinding marks, shear marks, and excessive mold lines.
Integrity: No cracks or underfilled areas (voids) permitted.
9. Rim Quality
The rim must be smooth, flat, and free of burrs, protrusions, or chips.
10. Cleanliness & Purity
General: The entire product must be clean inside and out, free of debris, dust, water marks, and glass particles.
Material Purity: No rust stains, black specks, or foreign inclusions allowed in the glass material.
Critical Note: Rust stains are usually caused by rusty clamps or molds during annealing and are permanent. Therefore, molds and clamps must be thoroughly derusted before production. Additionally, strict measures must be taken to prevent dust and impurities from falling into the molten glass during production.
