Ask Sam: What Causes That Line-Dried Freshness Smell?
Every other Friday on Morning Edition, the Outside/In team answers a question from a listener about the natural world.
This week, Jeff from Northwood asks: “What makes laundry smell nice and fresh when you hang it out to dry?”
Editor's Note: This edition of Ask Sam first aired in June, 2019.
This is an appropriate question to come from New Hampshire, given the state’s ties to the so-called “Right to Dry” campaign, which pushed back against condo associations that prohibited clothes lines because of the impropriety of seeing someone’s skivvies out on the line.
But where does that wonderful line dried smell come from? The obvious thing to point out is that line dried clothes smell nice because it smells nice outside. Fresh air, fresh laundry!
“Well you know it has everything to do with where we’re at,” explains Bob Monticello of the International Anti-Microbial Council, “If we hang out our laundry in a nice neighborhood where you have lots of fresh flowers and fragrances floating around, that’s gonna be trapped into the fabric.”
New Hampshire is the most tree-covered state in the nation, so even in our urban areas there are nice plant smells floating through the air settling into the folds of your fabrics, but by the same logic if you dry your clothes over a bubbling vat of Bolognese sauce, your clothes are going to smell like a bubbling vat of Bolognese sauce. (Which might be nice too!)
That was pretty obvious, but...
Are you ready to talk about bacteria?
“We never really get rid of the total bacterial load that’s on our fabrics even with washing and drying,” says Monticello.
Laundry has been getting more environmentally friendly, which means lower water temperatures and fewer harsh detergents. This translates to a lower impact on the world with each load of socks, but it does present a challenge: experiments have shown that you can put in a sterile cloth into a washing machine and it will come out with the same amount of bacteria as the dirty laundry loaded in with it.
(Note: while I do have a generalized rant that in our day-to-day life we should all just chill out about germs because the vast majority of that bacteria is harmless and trying to sterilize everything around us has harmful unintended consequences. However, I’ll keep my powder dry for the purposes of answering this question because it is bacteria that’s the source of these smells.)
So here’s the kicker: certain wavelengths of UV radiation blow apart the DNA of bacteria, which is why sunlight is a very cheap way to purify drinking water and if you’re in the back-country you can get portable UV lights to stick in your water bottle. In other words, line-drying doesn’t just add nice smells, it also helps kill the gross ones.
All just side-benefits. Freshness is the main event!
Sam Evans-Brown is the former host of NHPR’s Outside/In. Subscribe where-ever you get your podcasts. If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to email@example.com, OR call the hotline, 1-844-GO-OTTER.