Clothes washing mystery solved by physicists

Physics World ^ | 3 Apr, 2018 | Michael Allen

[MtnClimber]

A fresh water rinse is just as important as washing in detergent for getting your clothes clean, according to physicists in the US and the UK. They claim that the rinse cycle plays a key role in removing dirt from deep within textiles, by setting up chemical and electrolyte gradients that draw it out. This could lead to the development of more efficient and environmentally friendly washing machines, they add.

Washing machines wash clothes with water mixed with detergent and then rinse them with fresh water before finally spinning them. Washing detergents are surfactants, compounds that lower the surface tension between liquids and other substances, making it easier for them to mix. When washing clothes, they help the water mix with and loosen dirt on the fabric. Conventional understanding is that rinsing then flushes the fabric and washes the dirt away.

Stagnant cores

But, there is a problem with this idea. In most fabrics there are tiny pores that do not allow any significant fluid flow inside them. According to Sangwoo Shin at the University of Hawaii, Patrick Warren of Unilever in the UK and Howard Stone of Princeton University, it should take several hours for micron-sized particles to diffuse out these micrometre-sized pores. Yet significant numbers of particles do leave these pores on much faster time scales. The question as to how this is possible is known in the washing industry as the “stagnant core problem”.

Looking at this problem, the trio noted that when detergent-saturated fabric is exposed to fresh water the surfactant molecules rapidly move out of the stagnant core. They hypothesized that the surfactant gradient established when the fabric is rinsed – with a high concentration of surfactant within the fabric’s pores and a low concentration in the surrounding water –

[MtnClimber]

I think the lost socks and my right hand gloves could have had a transgender change into dark matter which we cannot see. They may be there, but we cannot see them.

[21twelve]

“The socks are probably where my right-handed work gloves are.”

I can’t recall if it was a comedian or a quirky commercial. But it has been theorized that those things get turned into all the extra Tupperware lids in the kitchen cabinet.

[Karliner]

My granny knew all about this. They stole her intel dammit!

[1_Rain_Drop]

"I was hoping this was going to solve the question of the disappearing socks."

Check under your bed.

[ANKE69]

That’s no mystery. The CAT takes the lost socks.... (in my house)! ;)

[KarlInOhio]

Once I'm done I put it back on the rinse cycle again (not a full wash/rinse).

Another thing is that I have given up on cold water washing and rinsing - always warm. I found a laundry chart that had various definitions and the one that jumped out at me was the temperatures. Warm was 95 degrees and cold was 80 degrees. That is way different from the water department's 50 degrees for cold water. If I took the time to put in a mixer on the cold water side to add some hot water to raise it up to 80° it might work, but 50° water just never got stuff clean if there was any real dirt on it. If I have something that demands cold water I just turn down the hot water knob so the washing machine's warm mixture is cooler.

[bluejean]

Oh crap. Now they’ll re-invent the washing machine AGAIN. The last iteration was epic fail compared to the old days. I just had to spend 250 dollars replacing the “sensor” chip on mine. The one that thinks and spins and ponders and thinks some more and spins the dry clothes for 10 minutes prior to the wash cycle beginning. This supposedly “balances” the load. But no worries, it’s got Energy Star built in, that little idiotic chip. I’m too stupid to layer the clothes in there anyhow, evidently.

[Hostage]

If you turn a right-handed glove inside out, is it still a right-handed glove?

[GOPJ]

The team also tested their theory on fabric. They found that a piece of cotton stained with polystyrene latex is cleaned better and faster when it is rinsed with fresh water after being soaked with detergent, than if it is rinsed with the same detergent solution (see figure).

That was my reaction too... who would ever rinse with detergent water?

[rolling_stone]

top loader-small socks etc usually get to the pump when the washer has been overloaded and it floats from the outer tub to the inner tub then to the drain hose/pump. Many top loaders can be cleared with a three barbed fishhook and lead weight on a line, dropped between the inner tub and outer tub and then the tub slowly spun by hand following slowly with the hook and line until the hook grabs the object, then just slowly retrieve the hook and item...there is no limit on socks you can sometimes find several of them.If you are lucky you can get the sock out without having to take the top off.

If they get to the pump you will probably y have to take the hose to the pump off to retrieve it. The most frustrating thing is an object like a quarter that gets to the drain hose and intermittently blocks the water like a ball valve depending on its position in the hose, horizontal or vertical.then there are small objects such as broken plastic or bra wires that come loose from frayed bras-that possibly can make it to the trap in the house drain, they act as a dam and lint slowly builds up behind them until the trap is blocked and you will need a flexible pipe cleaner/auger to get the rats nest of lint etc out of the trap.

the mesh bag and checking pockets for objects and bras for fraying and not overloading on high water level setting is the best prevention.

[Lean-Right]

While washing clothes in the dorm
laundromat, the washing machines
we’re regularly out of order.
Two sheets of bounce, dryer on high.
HOT is clean!

[GOP Poet]

coolio ;D

[taterjay]

These “studies” cost us...how much?

Followed by how much do these eco friendly washers cost????

[aquila48]

"I don’t understand the point of this article, of course you have to rinse soapy laundry with fresh water!!! What are you going to do, NOT rinse your laundry?"

Apparently that is what they did...from the article.

Rinse cycle: the top row shows fabric that is rinsed in fresh water, while the bottom row was rinsed in a detergent solution

[Eagles6]

My thoughts too. Why is it always the left one? ;-)

[deks]

the box of detergent contains only about 2% detergent. The rest is filler (ground up dog bones)

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Glad that I use liquid detergent... haven’t used powdered in decades.

[wbarmy]

I think the detergent and washing machine companies do these studies themselves to improve their product.

At least I hope so.

[Freedom_Is_Not_Free]

Water. The miracle fluid. God knew what he was doing when he made it.

[trebb]

I hear they will next tackle why it’s important to rinse with clear water to get shampoo (and the dirt and oils it dissolves) out of one’s hair.....couldn’t do the math them physicists did but could have come up with a very similar plain-speak explanation...

[raybbr]

No towels should be washed with softener - it makes them less absorbent.