Downward v. Upward
These are terms used to distinguish between two types of lake ice. One requires a covering of snow the other a covering of liquid water. Here in Virginia snow on the highways is not long lived. By day it tends to melt and then re-freeze as the sunsets. It is this melted liquid covering of the roadways called “black ice”. Compacted snow frozen into ice is full of air bubbles and the ice is “white ice“.
The New York Rangers and the Mighty Ducks demand a smooth, low friction black ice surface. That end is achieved with the aide of the Zamboni. The iceman drives it. He shaves the ice surface and then wets it down and then with the aid of cooling coils in, it freezes upward and the ice is black ice. Puddles on the highway likewise cool from the road bed upward and freezes the puddle upwards. My Honda wants nothing to do with black ice on the roadway. White ice at least has offers some traction to the careful driver. The unskilled black ice driver may end up doing a 180 or even a 360 spin across the road in fender-bender city. More high latitude ice life is mostly white ice that grows upward with each snowfall addition.
It is true that Hockey is exciting. But, in an Olympic winter games year there are lots other ice using sports that merit up close and personal attention. For example, skiing uses more bacteria than any other sport. The big dog on the slopes is the bacterium Pseudomonas syringae.
P. syringae made its grand entrance at the Calgary in 1985 and then again at Albertville in 1994. Genencor International, Inc. and its product SNOMAX is now almost everywhere. 100,000 gallons + 270 grams is the recipe for spray for the slopes. With SNOMAX snow production increased 25 to 60%. What a bargain! Genencor International, cultures P. syringae as you would for Budweiser yeast. Then grind it up. The ice nuclei (INA) are on the cell walls of the bacterium.
If you take small drop of distilled water and measure the temperature at the point of freezing. Look at your thermometer and it will read -40 C. This is the homogenous freezing point. If there is an ice nucleating material in the drop it will freeze at warmer temperatures. P. syringae will cause freezing at air temperatures as warm as -3 to -5 C.
Ice by Mariana Gosnell (2005) p.24
Biological Ice Nucleation and its Applications by R.E Lee, G. Warren and L. Gusta (1995) p. 342-344. APS Press.
Photo: Calle Eklund/V-wolf (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons