Laundry Science 101: Why Bubbles Don’t Equal Clean

October 15th, 2014 4:27 PM | 2 Comments

Let’s face it – looking into a washing machine and seeing lots of suds can make you feel like your clothes are getting clean. Suds don’t equal cleaning power, but a lot of people think they do.  On a psychological level people like to see something happening, but all you’re seeing is soap molecules trapping air in spherical pockets.  Trapped air in pockets doesn’t clean. The soap molecules in the water are what’s cleaning. Regardless, many commercial and soap manufacturers add chemicals specifically to create bubbles throughout washing, just to satisfy people when they look in their machine.

Laundry Science: Why bubbles have nothing to do with clean clothesYou may be curious as to why soap forms bubbles at all, and understanding what they are will also help you understand why they don’t mean anything. I wrote about how soap works in my surfactants post, but I will also explain it here a little more briefly.  Soap molecules have two ends kind of like a magnet. One end is attracted to water (think of this as the sticky side) and the other is repelled by water (but is attracted to dirt). Bubbles are formed because soap molecules will surround the water molecules with the “sticky” water-loving side pointed towards the water and the repellant sides pointed away.

So when you are looking at a soap bubble, you are seeing a thin layer of water sandwiched between soap molecules.  No matter what shape the bubble is initially, it will go into a sphere because that shape has less surface area which takes less energy to form (making it the easiest shape to form).

Now that you know that suds are just how soap molecules make a water/soap sandwich on the surface of the water, it’s easier to understand how this has nothing to do with cleaning clothes. All a bubble shows is how attracted the soap molecule is to water, and not how attracted it is to dirt. And while seeing a lack of suds in your machine may make you think there isn’t enough soap or there is no cleaning going on, just remember that different types of soap molecules make different types of bubbles. Some soaps hold bubbles longer or more easily than others. Some types of soaps make larger bubbles, some make smaller, some hardly make bubbles at all. Bubbles can also be affected by other ingredients also in the water. There are other factors that can impact the size of bubbles. Relating to laundry, people washing in hard water will see fewer suds than people washing in soft water. Temperature is also a factor as bubbles don’t form easily in cold water. 

Laundry Science - why seeing (or not seeing) bubbles has nothing to do with clean clothes!

In the case of HE machines, suds can be a bad thing. HE (High Efficiency) Machines require low sudsing detergents. This is because more suds can interfere with the tumbling action of the machine. HE machines rely on agitation – clothes tumbling and rubbing against one another – to clean. If a layer of bubbles forms between clothes, they aren’t going to agitate properly. With lots of bubbles, the clothes can form a bubbly layer of cushioning in between them, and if they are gliding instead of rubbing, they won’t be cleaned as well.

HE-symbol

It is because HE machines were designed around the agitation of fabrics that they also do not use as much water to clean. If your detergent is labeled as an HE detergent (Like Eco Nuts is), you aren’t going to see the same level of suds as a traditional detergent – and that’s nothing to worry about because it’s the soap in the water that is doing the cleaning. Remember the other side of the soap molecule – the side that hates water and loves dirt? That part works when the soap is in the water attracting to dirt on your clothes, holding onto the dirt and rinsing out.  Detergents that are labeled for HE can also be used just fine in regular machines, you won’t see as many suds but your clothes will still get just as clean – HE detergent just means low or no suds.

 

For more reading and photography credits:

http://www.cleaninginstitute.org/assets/1/page/he.pdf

http://en.wikipedia.org/wiki/Soap_bubble

http://blog.sciencegeekgirl.com/2009/05/02/why-does-soap-form-bubbles/

http://econutssoap.com/laundry-science-101-surfactants/

http://www.webexhibits.org/causesofcolor/15E.html

Laundry Science: Why bubbles have nothing to do with clean clothes

  • Observer

    Thank you Mona !

  • Leonard Martinez

    I read this piece as the washing machine was making loads of bubbles. I used too much detergent because I really did think the bubbles are what get the clothes clean. My bad. Now I know better thanks to you.