Soda-lime flat glass features stable chemical composition and natural anti-aging performance. Under normal outdoor natural conditions, sunlight, rain and fog will not degrade its structure, and it can resist weak acid and alkali corrosion. As confirmed in Pilkington’s official glass storage technical bulletin ATS-104, only two environmental factors drastically shorten glass service life: sustained high humidity and drastic temperature fluctuations, which trigger glass weathering (commonly called glass mildew or alkali backflow) during long-term warehouse storage or damp transit.
When glass sheets are stacked tightly in humid warehouses or soaked by rainwater, surface chemical reactions occur. Visible defects including rainbow iridescence, mildew spots, water stains, oil prints and paper grain marks will form on glass surfaces once exposed to light. Laminated glass faces higher mildew risks than regular untempered float glass, and untreated raw glass is far more vulnerable to alkali corrosion than pre-protected variants. Mild mildew can be cleaned with diluted white vinegar, yet severe alkali backflow leaves permanent irreversible damage.
Glass mildew causes multiple fatal losses for downstream processing. It lowers light transmittance and ruins optical performance; white haze and spots disrupt coating, mirror making and tempering deep processing; long-term corrosion weakens glass mechanical strength; heavy mildew leaves permanent hard-to-remove stains and even scratches sheet surfaces during unpacking. The glass industry adopts three mainstream cold-end anti-mold technologies to avoid such losses: interleaving anti-mold paper, anti-mold isolation powder and volatile anti-mold liquid.
The paper clip interleaving method uses moisture-absorbent special paper to block large-area glass surface scale formation. Higher-grade interleaving paper delivers better short-term anti-mold effects, yet its protective cycle is limited. If glass exceeds the paper’s valid storage period, residual paper scraps stick tightly to panels, causing stubborn contamination and surface abrasion during cleaning.
Anti-mold isolation powder is the most cost-effective, widely adopted industrial solution. Operators charge powder with static electricity before spraying, enabling even, firm adsorption on glass surfaces to isolate moisture and block ion exchange between glass and humid air. This method balances low cost and long-lasting protection for mass glass inventory.
The anti-mold liquid method relies on the agent’s volatility to inhibit water vapor condensation on glass. Workers evenly coat liquid on clean glass sheets and wait for full natural air-drying to form a continuous waterproof protective film without paper grain residues.
Apart from mildew risks, improper storage also triggers thermal cracking. Sudden temperature shock mostly appears on sunny winter days: low ambient temperature paired with direct solar heat creates uneven plane temperature differences on glass panels, generating thermal stress and cracks. Pilkington standards strictly prohibit open-air glass storage; if temporary outdoor placement is unavoidable, full light-shielding cloth coverage is mandatory to block direct sunlight.
To eliminate all storage defects, glass warehousing must follow standardized specifications:
Store glass far from construction zones, busy traffic routes and windy open areas to avoid vibration, dust and sudden temperature changes.
Choose dark, dry, ventilated indoor warehouses with complete roofs to avoid direct sunlight; untempered glass is more sensitive to thermal damage than tempered glass.
Place glass vertically at a 70°–80° angle against solid fixed supports. Lay soft cushion separators between every sheet, and elevate the bottom over 100mm with wooden or foam pads to isolate ground moisture.
Strict compliance with environmental control and stacking rules paired with matching anti-mold treatment can completely eliminate mildew and thermal cracking losses, preserving glass optical and mechanical performance for long-term storage and processing.
