Wednesday, 9 January 2013

Sweden Rocks and Ice: A Record Made of Ice

I was on a plane last week to Denmark and was talking to a Danish drummer.  We talked about how Sweden is influencing rock and pop music like never before.  Many of the most popular artists in America have Swedish song writers.  When Americans think of Sweden apparently they think of Swedish meatballs, the Swedish Chef and ABBA.  As stupid as that sounds it is true.  However, Swedish artists have established themselves into American music under the noise of most of Americans.  They are kicking ass there as well with many song writers and artists.  The ones I am listening to at the moment are Lykke Li and the Shout Out Louds. 

And from their great education system Swedes are also experimenting with more than just music as seen in Fast Company.  The Shout Out Louds are experimenting with making a record out of ice using distilled water.  They tried some other combinations of fluids using a home chemistry kit but settled on distilled water.  The problem they faced is getting all the bubbles out the water and problems with the mold.  One other problem is that the people have to wait six hours before the record is ready which is quite a long time for the die hard music enthusiast (but maybe a little waiting is not so bad in the instant download/instant gratification culture of today).  The Shout Out Louds could have used other liquids that make freezing faster or freezing the surface to be slightly different than the bulk but this could have been more troublesome.

What does this have to do with surface tension and water?  Surface tension depends on temperature.  There exists a surface stress imbalance when a the liquid interface is subject to different temperatures.  The dependence of surface tension on temperature can lead to the existence of a surface stress imbalance when a liquid interface is subject to variations in temperature. These stresses then lead to fluid motion along the interface.  For low fluids with a low Reynolds number (like those of polymers or viscous fluids) this motion along the interface rapidly leads to motion in the bulk of the fluid which in our case could affect the record.

The Surface Tension changes from freezing to boiling.  Below is a table showing the difference in surface tension.

Temperature deg C / Surface Tension (mN m-1)

The Swedes maybe did not realize that when they were freezing their record with just plane water they could have been doing a more interesting surface tension experiment cryogenic liquids.  These liquids would have a similar effect but would have used evaporative cooling and would have been faster.  Although this might have been significantly more difficult it would have given me something more to write about.  If they pursued this route I could have written about Thermocapillary Convection in Liquid Droplets also called Bénard–Marangoni convection.  This is interesting and its understanding is needed to make better computer chips for example.  If they made their record using this the dominant forces in this process of thermocapillary convection would be from buoyancy force and the surface tension.  Thermocapillary convection and marangoni effects are still being investigated on the international space station (ISS).