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How do the colour-absorbing sheets used in washing machines work?

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No one likes a whole white wash turned pink from the rogue red sock in the washing machine.

Asked by: Roger Britton, via email


Many fabric dyes are acids that form negatively charged molecules in water. The colour-absorbing sheets used in your laundry contain positively charged compounds that attract any dye molecules that leach out of coloured clothes.

Once the compounds have grabbed a dye molecule, a chemical bond forms that binds the dye to the sheet, so it won’t bleed out onto the laundry again. So the science behind it is sound, but modern dyes are much more colour-fast than they used to be, so colour-absorbing sheets are often unnecessary.

What happens to a teddy bear in a washing machine? © Getty Images


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luis villazon
Luis VillazonQ&A expert

Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.


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