Wednesday, March 21, 2007

Cr@zy Milk

by Godius (of shoutfile.com)

NOW… before you all go gettin’ all skeptical on me, I want you to know that I TRIED THIS. AND IT WORKS. Well, not maybe on the level they displayed on the video here, and without the music, but it did work.

This neat trick is the result of “soap-driven convection”, or the fluid movement of heated particles within the milk when it’s surface tension is weakened by another substance like a surfactant (soap) or an alcohol. Think of it like a soap bubble - what you are seeing when you see a soap bubble is actually water that has had its surface tension decreased so much that it expands to a bigger surface area. All of the moving colored swirls you see in a soap bubble are the surfactant working its magic, and when the surfactant has successfully moved through every particle of water, the bubble will break back into water droplets. This is exactly what is happening here, with the milk.

The #1 reason why my experiment did not end up like this one: I used cold milk, right out of the fridge. I saw an effect similar to this, but at a much slower rate, and with less dramatic of a result. If performing this experiment on your own, you would be best to use room temperature milk or milk that has been heated a little; the more heat the more energy, and the more energy, the more movement!

The #2 cause for my experiment’s differing reaction was that I used a lot more milk than I should have – one site I researched (after the fact) suggested using about 1/2” of milk in the bottom of a pie pan. I used about 3/4” of milk in a 6” round Tupperware. So certainly, with the higher volume of milk, there is a lot more to move around and a lot more area to cover!

Now what you have is a large pie plate (I would use a clear one) with approximately 1/2” of room-temp. milk in it. I also read that adding Isopropyl alcohol (90% is better than 70%) will help “speed things up” – just a drop of it will weaken the surface tension of the milk up even more, maybe the catalyst behind the above video’s rapid “effect”. The alcohol will eventually evaporate, so more will have to be added as it wears off.

Now, take some food coloring. I didn’t have eight colors; only four, so I had to work with that. I put 2 drops of each, red/yellow/green/blue, in that order clockwise around the outermost edge of the milk. You will notice the food coloring beginning to spread, but not nearly as much as it would had you dropped it into water. The milk is much heavier than water, and the food coloring will stay on top of it, which is the genius behind the whole operation here. Next, take your dish soap – I don’t think it particularly matters what kind – and add it to the plate of milk. You can do this by adding a few drops to the center of the plate, or add a dab to the tip of a Q-tip or toothpick and dip it into the center of the milk. DO NOT STIR – just be patient. You should start seeing the effect almost immediately.

The food coloring particles are basically water, and are lighter than the milk particles, so they “float” on top of the milk. When the soap begins to break down the surface tension of the milk and increase its surface “area” the food coloring goes with it. It will continue to move until all the soap particles have bonded with fatty particles in the milk and the surface tension is restored.

Definitely something fun, simple and cheap to entertain your kids for a while! You probably even have what you need to perform this one lying around your house right now… and if you’re really clever, you’ll have them believing that you are magic[al]!! It is also suggested to try this trick using different variables: warmer/colder milk, different fat contents (2%, whole, skim, etc.), and more/less soap or milk are all things you could try with this experiment.

Additional resources for Milk-Soap Driven Convection:

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