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How to Remove Grass Stains from Clothing

As the school year starts up again, we seem to find more and more grass stains on our clothing. With sporting events, children playing outside, it is a rare occasion to be completely stain-free. But why are grass stains so prevalent on cotton t-shirts and jeans? Why do grass stains seem to really “stick” to cotton and stain so deeply?
What is a grass stain?

In short, cotton is really good at binding dyes and colours into the fabric. At the same time, grass is essentially made of organic pigments. The pigments in grass bind to the cotton at the molecular level – making them difficult to remove.
Skip the next section to learn how to remove grass stains or, if you want to learn the science behind the stain, keep reading!
Molecular Make-up of Grass Stains:

Cotton is a polysaccharide made up of glucose units, with three hydroxyl (-OH) groups on each unit – meaning there are multiple sites for hydrogen bonding for the polar groups in dyes.

Molecular Make-up of Grass Stains

Grass is made up of carotenoids, such as xanthophylls, which are organic pigments or dyes.


Grass contains pigments that transfer to clothes, especially cotton, very well when they come in contact. This phenomenon is similar to making a tie-dye shirt where the dyes affix to a cotton shirt very well as shown in the illustration below.

organic pigment grass

At a molecular level, cotton sees grass as just another dye allowing the grass to create hydrogen bonds for the polar groups in dyes.
How to Remove Grass Stains:

Unlike the colours on our tie-dyed shirt, the pigments and dyes in grass not welcome! Treating with a product like Zout that contains enzymes will help breakdown the structure of the grass stain at the molecular level. After pre-treating with Zout, your detergent should be able to lift the stain and wash it away.

cotton molecule

On occasion the grass stain can be quite severe and then may require additional help in the form of a hydrogen peroxide containing product, such as Purex 2 Colour Safe Bleach, which is a good option. The peroxide reacts with any of the stain that might be left behind from the treatment with Zout and will cause it to “release” the shirt or clothing item.

cotton molecule

When using Purex 2 Colour Safe Bleach, the best way is to apply a little bit to the stain, gently rub it, and let it sit for five minutes. Then wash at the warmest setting that the clothing item will allow (consult the tag!) with your favourite detergent (which is, of course, Purex, right?) If this is a new product for you on a shirt that you’ve never pre-treated before, please test the product on the inside, such as on the hem. The fresher the stain, the easier it is to remove, so try to pre-treat and wash as soon as possible!
Last but not the least, don’t forget Purex plus Oxi liquid detergent, our most powerful detergent. It is a great choice for grass stain removal.

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