# Half-life of foams

1. Aug 4, 2004

### Telmerk

Hi!
I'd like to make some half-life measurements on water based foams. I have only simple instruments for it. Can anybody help me? I don't know the exact method that how to make this measurement correctly. And I also need the mathematical apparatus for it. Thanks a lot in advance!

2. Aug 4, 2004

water base foams??

3. Aug 4, 2004

### Telmerk

Half life measurement of foams

Yes, you know,water and some kind of detergent I mean.

4. Aug 4, 2004

thats gonna be very tough. You could do it by measuring your total mass of the water, then measuring the total mass of water + foam, and then measuting the mass of both at intervals and that sould give you enough information to set up an algebraic function of half life. H(t) = 1/2(a)^(t/h) (a = initial amount) (t = time) (h = half life)

5. Aug 5, 2004

### HallsofIvy

Do you have any reason to believe that foam has a "half-life"- that is, that the foam decreases exponentially?

6. Aug 5, 2004

### quarkman

There are awards given on the internet to people who spend thier time scientifically studying inherently silly things (I forget the name of the award). However, somebody proved that beer foam obeys the exponential law of decay!!!!! Why you would spend time researching this for your thesis is beyond me. :uhh:

7. Aug 6, 2004

### HallsofIvy

Hey, it sounds like a lot more fun than a lot of other topics! I can just imagine staggering across the stage to accept your degree!

Thanks for telling me that it IS exponential!

Telmerk: get a glass of beer (beer is, after all, "water based") and a ruler. Measure the height of the head above the beer. Record time and height. Wait a few minutes and measure again. Keep doing this until the foam has gone down to where you can't measure it.

The hard part: avoid drinking the beer until you are done!

8. Aug 9, 2004

### Telmerk

Thank You for your help! I made my measurements exactly like HallsofIvy suggested me, but not with beer, only with water and some detergent. I achieved exponential decay, but with high uncertanity. It is because it 's difficult to measure the exact height of the foam. (It's top is highly inhomogeneous--> I had to wipe away the foam hillocks. . )

So if someone has an idea how to make more exact measures, please write it to me.

I think half life in case of foams means the time elapsed until the half of the initial foam height is reached and not the half mass.

Dear quarkman, it may seem to be a silly thing, but foams and foam structure appear almost every field of science: from cosmology trough food industry (beer:-)) to materials science.

Thank you guys again!
Cheers!

9. Aug 9, 2004

### quarkman

Telmerk, I realize it is closed-minded of me to laugh at someone who learns just for the sake of knowing...I learn about "silly things" (depending on your perspecitve) all the time. I just find it amusing that someone recieved a graduate degree for researching beer...something which I feel should not be the foremost thought on a graduate student's mind. For instance, if I drink to much beer, I do REALLY stupid things and find it hard to read and understand things. I really love to read about science and learn new things, so I consider beer drinking bad in that respect. But you are right, foams are important in many aspects of daily life. I remember researching "piezoelectric polymer thin films (foams)" as an undergraduate student and when I came across the statment that wood was a foam, something I should have known as a physicist, I was really shocked. I mean it doesnt look like one even after you break it open!! I guess I wish this beer foam guy had attached his findings to beer, soda, and other carbonated drinks. He may have, but then inaccurate reporting is to blame there..... :uhh: