Do we still need to separate colours? Kiwi chemistry expert separates fact from fiction when it comes to laundry

Exhausted mum prepares to do laundry load with kids on either side of her
Modern dyeing techniques mean most clothes are colour-fast - but proceed with caution when they're new, says Dr Jack Chen. Photo credit: Getty Images

From RNZ's Sunday Morning

A Kiwi chemistry expert separates fact from fiction when it comes to doing our laundry.

Are jeans best left unwashed? Is fabric softener bad for our clothes? Do we really need to separate our whites and colours?  

Jack Chen, senior lecturer in chemistry at Auckland University of Technology, was responding to reports that we no longer need to separate our laundry.

He told Sunday Morning it was true that the natural fibres and dyes had been replaced by synthetic fibres and better dyeing processes that stood up to washing. 

"But I probably still wouldn't risk putting coloured clothes that hadn't been washed before with whites."

He agreed colder temperatures and using less detergent kept colours from fading and whites bright.

"With lower temperatures, there's less risk of dyes from coloured clothing coming off and depositing on white clothing."

On the topic of keeping outdoor clothing or active wear separate to the rest of our washing, he was less convinced. 

"That's news to me - I've always washed my sports clothing together with the rest of my clothes."

However, most water repellent clothing had been treated with chemicals known as per and poly-fluoroalkyl chemicals [PFAS] - the sort found on Teflon-coated pans.

"These chemicals are designed to repel both water and oil. If that's the case, you would need harsher detergents to clean that properly."

The jury was out on how often to wash jeans - while some say never, others have suggested they should be washed every four or five wears to get rid of bacteria

"If you've got bacteria anywhere you want to be washing that off, especially with odours, I don't think jeans are immune - I definitely still wash them regularly," Dr Chen said.

As to the "rule" about not using fabric softener in every wash, as it left behind a coating that made them less absorbent, this was true, he said.

"Fabric softener applies a layer to your clothing and makes it feel smoother. Especially with things like sportswear you definitely don't want to be using it because that film will clog up the pores and make your clothing less breathable.

"It will be absolutely fine on things like towels and underwear if you like that soft feel, just not sportswear."