I used to find that even with weekly washes, my dazzling white bed sheets quickly faded to gray. Months of detergent build-up to remove yellow bedding stains left a film on my bedding, a problem worsened in hard water areas, as mineral deposits add another layer of dullness.My first instinct was bleach and a hot wash. However, while chlorine bleach can strip away soap residue, chlorine reacts with mineral build-up to lock in hard-water film. Despite the heavy washing, my gray sheets were even duller.But I've found a fix. This simple two-step pre-wash soak starts with oxygen bleach and dish soap to lift leftover detergent, and finishes white vinegar to cut through gray film. My sheets are back to their sparkling white best — here's how.Read more: The best bed sheets for every budget

(Image credit: Future)The 2-step pre-wash laundry soakThese ingredients are safe to use on most fabrics. However, oxygen bleach should be kept away from silk, wool and leather (plus anything with wooden buttons), while vinegar shouldn't be used on delicate materials such as silk and rayon.Our first hero ingredient is oxygen bleach. This mild bleach contains either sodium percarbonate, hydrogen peroxide or sodium perborate, which form bubbles when mixed with water. These oxygen bubbles help gently lift away stains and gray film, without damaging the fabrics.Adding a squirt of dish soap helps boost the stain removal. Dish soap is good at breaking down oils and grease (hence why you use it on your dirty dishes.) In this pre-soak, it helps lift the oily film left behind by your detergent.Step two involves white vinegar. This kitchen staple is a cleaning must-have, used for everything from freshening up toilets to washing pillows. Vinegar contains acetic acid, which cuts through the gray grease of soap residue. It also breaks down mineral deposits, like the calcium left from hard water.Get instant access to breaking news, the hottest reviews, great deals and helpful tips.