Science Questions

Do bubbles hinder cleaning dishes?

Sat, 6th Aug 2011

Listen Now    Download as mp3 from the show Do bubbles help washing up?

Question

Caroline asked:

Hi,

 

People say that bubbles & foam make no difference, or even hinder, when cleaning dishes (or hair or whatever) is this true?

 

Kind regards,

 

Caroline Greville

Answer

Dave -  I think yes and no.  You tend to get bubbles when you're using some kind of detergent.  Detergents break down the surface tension of water which makes it a lot easier for it to dissolve things like fat - little molecules with oil loving tails and water loving heads.  The detergent sticks to the fat, and dissolve it, and that it will still have the side effect of forming foams quite easily.  Having a very stable foam though, which will sit on the surface of your washing bucket, isn't vital for actually doing the cleaning.  That's just aesthetic mostly and if you're in a dishwasher or something, it actually really hinders it...

Chris -  Or washing machine.

Dave -  ...or washing machine.  Actually, the washing machine is quite interesting.  In the States, they don't make foam at all because they have top loading washing machines so you can't see inside.  In Europe, we have side loading washing machines that we can see inside.  They make a bit of foam, but having too much would stop the clothes moving around properly or block the jets of water in the dishwasher from hitting the dishes, and therefore they wouldn’t clean as well.  But with washing up water, I'm not entirely sure it’s a bad thing because it will act to insulate the water, so if you're doing a lot of washing up and you've got a lot of foam on the top, it will actually keep it warmer for longer and heat is very, very important for cleaning.  So I think it probably does help but not the way you think it does.

Chris -  Can you help me out on this one because my mum told me an old wife’s tale which I think is true which is: if you've got biological washing powder which doesn’t have an anti-foaming agent, it’s not automatic washing powder, and you need to use it in a machine, you can put a cake of soap inside the machine and it stops it frothing up.  And if indeed, you do have bubbles in the bath because I used to have a lot of bubble bath when I was a kid – if you put the soap in the bath, the bubbles will break down.  So what's in the soap that actually doesn’t agree with the bubble mixture?

Dave -  I'm not entirely sure.  I’d have thought you're getting a reaction between the two detergent molecules and you're forming little micelles inside the water which are basically all the tails of one detergent molecule meeting up with the tails of the other one. You form little balls of detergent inside the water rather than sitting on the surface and making foam.

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