A Chemist Looks at Skiing
....For some ridiculous reason to which I however have no
reason to be disloyal...
Some person in authority, I don't know who, very likely the
astronomer royal...
Has decided that although for such a beastly month as
February,
twenty-eight days as a rule are plenty...
The Pirate King in Pirates of Penzance
February a beastly month?!?!
Not for anyone who loves winter sports and especially
skiing.
When I was a very young man I had an aunt living in Norway
who eschewed all modern technology and still used rabbit skins on the bottoms
of her cross country skis. For the
rest of, us the sport of skiing uses a plethora of engineered materials, high
tech engineering, and even biotechnology.
Chemistry makes it all possible.
To anyone standing on bare winter ground and looking up at a
snow-covered mountain the most basic ski technology, snowmaking, is immediately
obvious. Although there were some
earlier experiments with blocks of ice and wood chippers, the basic snowmaking
technology we use today emerged in the mid-1950s. Ski area operators in New England had always been proud of
the region's reliable snowfall and could usually count on good winter weather. But a few lean years convinced them to
install the first snowmaking systems at Mount Ascutney in Vermont. Other pioneer systems were installed at
resorts in New Hampshire, New York, and Pennsylvania by the start of the 1957
season. According to the New
England Ski Museum of Franconia, New Hampshire, the first snowmaking systems
originated with de-icing technology.
Throughout the 1940s aviation engineers were experimenting with de-icing
systems for aircraft but the test these systems it was first necessary to
create ice. The principles of
these systems were later adapted to postwar snowmaking.
The basic snowmaking system uses compressed air that is
mixed with water and shot out of jets (called "guns") placed on the
ski trails. The first commercially
successful snowmaking systems were of this type and were developed by the
Larchmont Engineering Company of Lexington, Massachusetts. The high pressure air (typically 110
psi or 758 kPa) disperses minute water droplets into freezing ambient air. The resulting crystal structure is
actually similar to natural snow.
With proper adjustment of air pressure the man-made snow will have a
crystal lattice structure very similar to natural snow. Regulating water content controls the
texture of the snow. Wetter snow
can be laid down as a base and a lighter powdery snow can be added to the top
of it. According the Ratnick
Industries, a leading manufacturer of snowmaking equipment, a typical air-water
snowmaking system can be used at temperatures under 31¡F (-.5¡C) wet bulb
temperature. In conditions of
higher humidity, snow can be made at higher temperatures, 36¡F (+2.2¡C) / 30%
relative humidity and 34¡F (+1.1¡C) / 40% relative humidity.
During the 1930s major department stores in Newark and New
York City featured indoor ski slopes where customers could test new equipment
before buying. The indoor ski run
in Bamberger's was sixty feet long and covered with borax crystals. In the mid 1950s experiments were made
with various types of synthetic snows.
In Nuremburg, Germany, wastes from a porcelain factory were piled into a
200-foot high hill. Other German
ski centers used plastic mats laid down on peat. There was no engineering reason for using peat, it was thought
that it might be softer when a person fell! A ski center in Newton, Massachusetts, used plastic pellets
instead of snow and waste from nearby plastics factories was used at Beacon,
New York for the ski jump and small practice hill.
Also in this period, the standard ski technology, knot-free
hickory wood with metal edges, began to be replaced by other materials. Skis made with laminations of hickory
and aluminum, or fiberglass, and even plastic were on the market by 1951. It was not until the middle of the
1950s that the Hart Ski Company and its rival, Head Skis, both brought out
commercially successful metal skis.
Although developed in the United States, metal skis made gained
international recognition when they were used by the French Ski Team in the
1960 Squaw Valley Olympics. In the
mid-1960s Hart was manufacturing 144,000 pairs of skis per year. But by 1969 fiberglass skis were
introduced and soon made metal skis obsolete. It was at this time that plastic boots began to replace
leather ski boots.
Whatever the tops were made of, the bottom of skis (of ski
soles) must be covered with an hydrophobic waxy substance that will cause the
ski to glide over the thin layer of water created when the pressure of the ski
momentarily melts some snow. Ski
waxes lower the surface tension between the water and the ski sole. They also reduce mechanical friction by
eliminating surface roughness and irregularities in the sole. Most ski waxes were and still are made
from paraffin but in 1985 fluorinated ski waxes became available. In these waxes, hydrogen atoms in the
paraffin are completely substituted with fluorine atoms. For example, the wax that had been
manufactured by 3M, FC-740, consisted of a nonionic fluoroaliphatic polymeric
ester. These waxes have extremely
low surface tensions and increased dirt repellence.
Most recreational skis only require an occasional coat of
wax because their bottoms are made of a waxy, self lubricating plastic. The first of these materials was
introduced in 1957 and sold under the trade name Huski TF-2. The soles were sold not to ski
manufactures, but as kits so that skiers could convert their own equipment to
the new technology. The common
technology today employed today is the sintered base. These are made from polyethylene which is subjected to an
heat processing step that creates a thin, highly porous, polymer. This polymer is then laminated onto the
base of a ski. The exact
composition of the polymer can be modified to create different performance
characteristics. Waxes are then
added to fill the pores and coat the surface.
Alpine skiing started in New Jersey began in 1937 when
Austrian emigrant, Hugo Muiry, founded the Craigmeur ski area near
Newfoundland. Lights for night
skiing were installed in 1942 and snowmaking followed in 1955. The largest ski areas in the state were
both located on Hamburg Mountain in Vernon. Great Gorge and Vernon Valley began operations as separate
ski centers but later merged into one operation. Today the combined areas known as Mountain Creek are
operated by the Crystal Springs Resort.
By 1967 the Great Gorge ski area on had 90 snowmaking guns
and a mere 14 miles of fiberglass pipes.
(Today the resort has about 1,000 guns to cover its 41 trails) In 1971 the resort used a
Curtiss-Wright jet engine to replace multiple 450 horsepower diesel powered
compressors that provided air to its 120 snowmaking guns. The $400,000 Great Gorge system was
actually a small installation.
Some resorts employed 4,500 pound, 7,000 horsepower Curtis-Wright J-65
jet engines. These were the same
engines that were used on the B-57 twin-engine bomber and the A-4 fighter
plane. This type of system was
thought appropriate for New Jersey were periods of freezing weather do not last
as long as they do in New England.
Snow must be made quickly and the system allowed Great Gorge to make six
inches of snow in 24 hours.
As time went on new snowmaking technologies were introduced
that promised to cut down on the expense of providing compressed air from a
central station or banks of mountainside compressors. A system made by Germany's Linde Corporation used an
electrically powered turbine to run an on-board air compressor and blower
fan. The compressor was also used
to chill the water and enhance snowmaking capacity. Snow Machines International of Tuxedo, New York, developed
the SMI machine at this time.
Called a "five and dime" snowmaker because of its low cost,
simplicity, and small size. the SMI used a 5 horsepower electric motor to turn
fan blades. Water was pumped into
the hub of the fan where it traveled out along the blades and was cooled to
between 10 and 15 degrees F by the time it reached the tips. The rotating fan blew the snow onto the
hill. The SMI system could not
throw the snow as far as compressed air systems so that snowmaking crews had to
reposition them more often, but it was cheaper to operate. The Hedco system, invented by a cloud
seeding expert from Bedford, Massachusetts. This system was introduced in 1971 and used minute particles
to serve as snowflake nuclei. Like
the Linde and SMI systems a separate supply of compressed air was not
required. Another advantage was
that the size of the nuclei could be adjusted for different weather
conditions.
An alternative to forming snow from a mixture air and water
was tested at four Colorado ski areas in the winter of 1984-85. Snowmax was a bacterium sold by
Advanced Genetic Sciences of Berkeley, California. Pseudomonas syringae
is found on the foliage of many broad leaf plants including vegetables, fruits,
and flowers. It has the property
of forming tiny ice crystals although at the time scientists with Advanced
Genetic Sciences admitted they did know how. (It was later found that the protein responsible for the
process was found in the cell walls.)
Pseudomonas syringae would
continue to produce ice crystals even when dead. Snowmax was a mix of dead bacteria and small particles that
provided nuclei around which the bacterium's ice would form. It was applied to the ski trails
through underground pipes. The
system did not require compressed air and was claimed to be between 20 and 80%
more efficient than conventional snowmaking.
The results of preliminary tests were mixed. Winds at the Breckenridge ski resort
made effective application difficult but at Copper Mountain the application was
more effective. However high winds
developed periodically, disturbing the process, and obscuring the results of
the tests. Winds were the greatest
danger associated with the process.
Some scientists in Colorado feared that if the bacteria was blown off
the mountain it could damage frost-sensitive crops. The high concentration of the bacterium and the fact that it
would be applied in the spring and fall when crops were most vulnerable made
the possibility of escape all the more alarming. There was however little concern over human health, Pseudomonas
syringae is a naturally occurring species
and people come into contact with it frequently. Additionally, there were no genetic modifications to the
bacterium. Today Snowmax is sold
as a protein-based additive for conventional snowmaking systems. It serves as a nucleating agent and
also enhances ice crystal formation so that snow can be made at higher
temperatures. While some
environmental concerns remain, the agent is used widely and there is some
evidence that the snow produced with it lasts longer.
An example of the complex snowmaking infrastructure of a
modern resort is Windham Mountain, located southwest of Albany, New York. This Catskill Mountains resort claims
to have the most snowmaking coverage of any mountain within 200 miles of New
York City. The mountain is
crisscrossed with a network of 65 miles of pipes supplemented by 25 additional
miles of hose. The system can
deliver 6,000 gallons of water per minute to the trails pushed by 30,000 cubic
feet of air per minute at 110-114 psi.
So the next time your boss catches you sneaking out of the
lab to go skiing, you can quite rightly claim that you are still doing
chemistry!
For those readers who hate winter, I will be doing a story
on the chemistry of the Jersey Shore in an upcoming issue.
Kevin Olsen
Montclair State University
For More Information:
Skiing in New Jersey, by Elizabeth Holste, ISBN:
978-1-4116-6037-3
New England Ski Museum, Franconia, NH,
http://www.skimuseum.org/