How to Bleach Polyester Whites

Polyester fabric has its advantages and disadvantages, and one of the latter is that its fibers can be irreparably damaged by regular bleach. An additional risk is that instead of whitening a polyester item, bleach can turn it a dull yellow hue that's tricky to get out. If liquid chlorine bleach is your go-to for getting stains and dinginess out of whites, know that it's important to use caution when those whites are made from 100 percent polyester. Given the risks, it's generally better to use polyester-safe oxygen bleach, which is gentler and comes in a powdered form. Doing so takes a bit more patience than is needed with chlorine bleach, but it's a safe and effective alternative.

You might have seen polyester listed as one of the fabrics that cannot be bleached, but it is in fact possible to use bleach on white polyester fabrics with good results. The key is to make sure the chlorine bleach is very diluted – never apply it neat – and that the soaking time is very short. A brief presoak in a solution of 3 to 4 tablespoons of chlorine bleach per gallon of cool water can bleach polyester whites back to a bright white and lift minor stains. Soak the item for a maximum of 5 minutes, drain the bleach solution and immediately wash the item with laundry detergent plus 1/2 cup of bleach.

While the small amount of diluted bleach and short soaking time with this method make it generally safe for washing white polyester fabrics, you should only do so irregularly. Don't be tempted to immediately repeat the process, even if the results are not to your liking. It's also a good idea to try alternative methods to bleaching polyester whites first, especially if the item is difficult to replace.

Unlike chlorine bleach, some brands of oxygen bleach are labeled as safe for use on polyester and other fabrics that cannot be bleached. Using one of these brands and following the manufacturer's directions is the safest option for bleaching polyester whites. It can be used on colored polyester fabrics as well, as it will not typically lighten the color of polyester. Another advantage of oxygen bleach is that you can lengthen or repeat the presoak if needed without risk of damaging the fabric.

While highly effective at brightening whites and removing stains, using oxygen bleach does require a lengthy presoak. Follow the manufacturer's directions, which generally tell you to add around 1/2 cup of oxygen bleach powder per gallon of hot water, stir to dissolve and submerge the fabric item in the solution. You might need to sit a heavy plate or something similar on top to keep the fabric submerged for the full presoak time of eight hours or more. If your washing machine has a presoak option, use this instead. After soaking, drain the solution and launder the polyester fabric as usual at the hottest temperature recommended on its label.

It is not safe or effective to try to bleach colored polyester fabric until it's white. While this method is common with colored cotton fabrics, the strength and time frame needed to lift or even lighten the color of polyester will ruin the fabric. If you need to lift or lighten the color of polyester fabric, look into color-stripping products designed for use on polyester.

Before using chlorine bleach on polyester, check to make sure it doesn't contain spandex, also known as Lycra or elastane. Any amount of bleach will damage those fibers beyond repair.

If an attempt at bleaching polyester whites has left a yellow tinge to the fabric, try removing it with borax. Mix 1 to 2 tablespoons of borax in hot water and add it to a regular wash cycle.

Consult a dry cleaner for tough stains or extra-dingy white polyester fabrics that are especially valuable or irreplaceable.