Sun-bleach fabrics on grass or a flat surface

Wet the yellowed fabric thoroughly, lay it flat on clean grass or a white sheet in direct sunlight, and keep it damp throughout the day. Turn it over halfway through. Repeat over several days until the desired whiteness is achieved.

Why It Works

UV radiation photochemically breaks down the natural pigments and chromophores that cause yellowing in cellulose fibers. Moisture on the fabric generates reactive oxygen species that further oxidize discolorations. This method, called "grassing" or "crofting," has been used for thousands of years.

Tips

• Re-wet the fabric periodically so it stays damp during sun exposure
• Works on both cotton and linen, though linen takes longer due to its higher non-cellulose content
• Avoid this method on vegetable-dyed fabrics, which will fade rapidly in UV light
• Best results come in summer with strong, sustained sunlight