When sourcing white dresses, fabric opacity (GSM) is the most critical factor to prevent transparency. For professional or formal wear, look for a minimum weight of 180-220 GSM. Preferred materials include long-staple cotton, mulberry silk, or high-density polyester blends with anti-yellowing treatments. Ensure the supplier uses optical white dyes that maintain brightness after multiple washes and check for lining specifications, typically requiring a soft habotai or lightweight jersey lining for comfort and modesty.