Tomato sauce on a T-shirt or dirt on a towel: Bleaching agents are a go-to weapon in the war against stubborn stains.

The triangle symbol on a garment’s care label indicates whether textiles are suitable for bleaching.

If the triangle is crossed out, it means do not bleach. The garment should then be washed only with colour or mild detergent, because full or universal detergents contain bleach.

A triangle with a white surface, on the other hand, indicates that the textile is suitable to be treated with chlorine or oxygen bleach.

“Chlorine bleach works in a very short time and at room temperature even against stubborn coloured stains,” explains Bernd Glassl of IKW, a German detergent association.

It’s the best option for white textiles, such as linen or cotton.

Detergents containing active chlorine bleach are unsuitable for most coloured clothes. Bleaching attacks the dyes contained in clothing, so the treated area on a grey garment can turn orange, Glassl says.

If you try to remove a fruit stain on blue jeans with chlorine bleach, the spot will turn white.

Oxygen bleach is an alternative to more aggressive chlorine bleach.

On the textile care label, a triangle with two diagonal stripes indicates that treatment with oxygen bleach is suitable.

Universal detergents in powder, tablet or granulate form contain oxygen-based bleaching agents, Glassl says. They also contain a bleach activator, which makes the bleaching effective from 40 degrees Celsius. If you wash coloured garments several times with a full or universal detergent, the intensity of the colours will decrease, he explains. Black clothing will eventually turn dark grey after some time. How quickly this happens depends on the quality of the dye.

An alternative for treating fruit and vegetable stains is gall soap, especially if you treat the stain immediately, Glassl says.

Special stain removers can help, but they often contain oxygen-based bleaches. But if you’re not using the product frequently and repeatedly in the same place, the reduction in colour intensity should be barely noticeable. – dpa