© | Dror Bar-Natan's Image Gallery: Miscellaneous: screen version   print version

Milk Drops

On June 23, 2002, I took around 415 pictures of milk drops falling into a bowl of milk or a shallow puddle of milk. Here are the best 20 of the roughly 100 that actually had something in them. I don't have the equipment to take very rapid shots, and hence each frame came from a different drop, which were dropped from different heights. I tried to arrange them in "process order", but I'm not at all sure I understand the process well enough to have done it correctly!

First, here's a drop right before the splash. I estimate its diameter at about 4mm.
640x480 1280x960
A Milk Drop
A 4mm milk drop right before the splash.
When the drop hits the surface, it creates an outgoing shock wave, which crests and becomes "a crown".
640x480 1280x960
An Emerging Crown
An outgoing shock wave - an emerging crown.
640x480 1200x900
A Crown
A crown produced by a drop of milk.
After the crown falls, all is left is a crater. The secondary milk drop seen is perhaps the tail of the original one, which splits off and falls more slowly because its relative surface area is bigger.
640x480 1024x768
A Crater in a Milk Bowl (1)
A crater produced by a milk drop.
640x480 1280x960
A Crater in a Milk Bowl (2)
A crater produced by a milk drop.
640x480 1280x960
A Crater in a Milk Bowl (3)
A crater produced by a milk drop.
Here the crater had refilled, and the impact of the secondary drop created a "crater within a crater":
640x480 1280x960
A Double Crater
A crater within a crater in a milk bowl.
When the crater refills, it closes up with such a force that a column of milk shoots up and then falls down:
640x480 1280x960
A Column of Milk (1)
A column of milk shoots out following the impact of a milk drop (beginning).
640x480 1280x960
A Column of Milk (2)
A column of milk shoots out following the impact of a milk drop (at highest).
640x480 1280x960
A Column of Milk (3)
A column of milk shoots out following the impact of a milk drop (now falls back).
640x480 1280x960
A Column of Milk (4)
A column of milk shoots out following the impact of a milk drop (now falls back).
640x480 1280x960
A Column of Milk (5)
A column of milk shoots out following the impact of a milk drop (now fully collapsed).
640x480 1280x960
A Column of Milk (6)
A column of milk shoots out following the impact of a milk drop, collapses, and a secondary column emerges.

Now on to some pictures of splashes into a shallow layer of milk:

640x480 960x720
A Splash of Milk (1)
A splash created by the fall of a milk drop into a milk puddle.
640x480 1280x960
A Splash of Milk (2)
A splash created by the fall of a milk drop into a milk puddle.
640x480 1280x960
A Splash of Milk (3)
A splash created by the fall of a milk drop into a milk puddle.
This nice crown-splash has a secondary drop about to hit its middle:
640x480 1280x960
A Crown-Splash of Milk and a Drop
A splash created by a milk drop in a milk puddle and a secondary drop.
In these two pictures the secondary drop falls back and creates a secondary crown-splash:
640x480
Nested Splashes of Milk (1)
Nested splashes of milk.
640x480 1280x960
Nested Splashes of Milk (2)
Nested splashes of milk.
Finally, here's a collapsed crown, with a secondary crown in the middle, and a ternary drop about to splash:
640x480
Nested Splashes of Milk and a Ternary Drop
Nested splashes of milk and a ternary drop about to hit.

Do it yourself! I took a milk carton, stuffed its opening with a paper towel and let it stand sloped down on a chair, so that I got a constant flow of milk drops down to the floor, at a rate of one per maybe 10 seconds. Down below was the bowl/puddle, and around 30 centimeters away I had my camera on a tripod, focused manually on the impact point. I used the camera's flash as a strobe light to hold the motion, and also used a very fast exposure time - 1/1000sec or so. The point of the fast exposure was not to hold the motion - that was achieved by the flash - it was just to make sure that from the perspective of ambient lighting the pictures would be hugely underexposed. So I could play with everything at normal room lighting and yet have a dark room and a strobe light in as much as the camera was concerned. With this setup I took my 415 pictures or so, watching each one on the screen of my digital camera and getting better at synchronizing with the drops as I went along. I'm sure you can do better!

Environmental Statement: The bowl I used is tiny (8cm diameter, 2cm deep) and in total I used less than half a cup of milk.