Oxygen bleach or chlorine bleach — which is better for food and grass stains

Chlorine bleach takes the color out of a stain, but the fabric takes a hit too. A laundry guide from Texas A&M University advises using it only on white and colorfast clothes and warns that with frequent use it weakens fibers, especially cotton, so clothes wear out faster.

A 2023 lab experiment measured how much weaker cotton gets. Cotton fabric was washed in a chlorine solution, the way it's done in an industrial laundry. After just five washes the fabric could hold 16% less load before breaking, after ten washes 50% less and after a hundred 80% less. The fabric turned yellow, felt stiffer and sometimes tore with normal handling.

For comparison, the same cotton fabric after a hundred regular industrial washes got 29% weaker along the warp threads, which run the length of the fabric, and 15% weaker along the weft threads, which run across it. The author of this experiment writes that cotton is especially vulnerable to chlorine above 68 °F (20 °C).

But this was one fabric in a lab, and the solution was like an industrial laundry's, not like a wash at home. We don't apply these numbers directly to home laundry.

Bleach has other downsides too. A New Mexico State University guide says it can make some yellow stains worse and put holes in fabric, and with iron, which is sometimes in water, it leaves rust stains. According to a University of Kentucky guide, a rust stain becomes permanent after chlorine bleach.

Silk, wool and stretchy fabrics with spandex shouldn't be bleached with chlorine at all. All three university guides say so.

No, they're different substances. Regular household bleach is chlorine bleach, and it's based on sodium hypochlorite. According to the UK Health Security Agency (UKHSA), household products contain up to 10% of it.

Oxygen bleach is based on something else, sodium percarbonate. In water it dissolves quickly and breaks down into sodium carbonate, also known as washing soda, and hydrogen peroxide. That's what HERA, a European risk assessment of percarbonate, says. The report was prepared by Solvay, a company that makes percarbonate.

Laundry detergents and laundry additives also often contain TAED, a bleach activator. Together with peroxide it forms peracetic acid in the wash water, and that acid oxidizes stains. According to HERA, in a typical European wash at 86 to 140 °F (30 to 60 °C), this reaction is done within 15 minutes.

To be fair, oxygen bleach has its weak spots too. The University of Kentucky guide says chlorine bleach works more strongly than oxygen bleach, though it can damage some fibers, dyes and finishes. And the New Mexico State University guide says most oxygen bleaches work best in hot water.

Hydrogen peroxide isn't completely harmless to fabric either. The author of the 2023 cotton experiment lists substances that release chlorine or hydrogen peroxide among the causes of fabric weakening. But in another lab experiment from 2021, 3% hydrogen peroxide was added to a low-temperature home wash, and the laundry didn't lose color and its tensile strength didn't change.

Cold. The University of Kentucky guide sorts stains into groups and puts grass in the protein group along with blood, egg and milk. Fresh protein stains come out if you soak the item and swish it around in cold water before washing.

If you start with hot water, it "cooks" the protein. The protein sets between the fibers of the threads, and the stain gets harder to remove. The New Mexico State University guide advises soaking fresh blood, egg or ketchup stains in cool water for half an hour or longer and then rubbing them gently.

So green knees from a grassy field or a walk in the fall park go into a basin of cold water first, not into boiling water.

Hydrogen peroxide has its own trouble with blood. In the 2021 lab experiment, every test stain washed out better with peroxide except one, a mix of blood, milk and ink. The authors explain this by a reaction between the iron in hemoglobin, which is in blood, and the peroxide.

There are also enzyme products for protein stains. The Kentucky guide notes that enzymes digest protein and doesn't recommend these products for silk and wool.

For another group of stains, tannin stains, the rule is the opposite. They're left by plant compounds called tannins. The Kentucky guide lists stains from berries, including cranberries, raspberries and strawberries, from fruit juices, tea, coffee, tomato juice, beer and other alcoholic drinks in this group. According to the same guide, fresh tannin stains usually wash out with detergent in hot water if the fabric can take it, and old ones may need bleach to come out completely. So drops of cranberry sauce and juice on the holiday tablecloth, unlike grass on jeans, get washed in hot water if the fabric can handle it.

Not until the stain is gone. The New Mexico State University stain removal guide says plainly that heat sets stains, so fabric with a stain shouldn't be ironed or put in the dryer.

Here's a familiar story. Soup splashes on your jeans, you wash them with detergent and a brush, and as they dry the stains show up again. It's better not to iron them or put them in the dryer, but to treat the stain one more time.

Yes, if the care label allows it. One of the care symbols is a triangle, and GINETEX, the European association for textile care labeling, explains it this way. An empty triangle allows any bleach, chlorine or oxygen, and a triangle with two diagonal lines allows only oxygen bleach, meaning non-chlorine bleach.

GINETEX advises against bleaching colored items with oxygen, including with an all-purpose detergent that contains it, unless the symbol allows it, or the color may change. American university guides are bolder about oxygen bleach and recommend it for colored fabrics too, but we stick with the cautious option and check the label.

The FTC's Care Labeling Rule in the US also separates two cases. If chlorine bleach would harm an item with regular use but non-chlorine bleach wouldn't, the label must say "Only non-chlorine bleach, when needed." If all bleaches would harm it, the label says "Do not bleach."

People often ask if you can wash any fabric with oxygen bleach, and the answer is no, not any fabric. Colored items can be bleached with it only if the label shows an empty triangle or a triangle with two diagonal lines, and if it says "Do not bleach," no bleach is right for it.