how to model
Snow is one of those very complex things that
requires careful study before embarking on modelling. Snow is actually
precipitation in the form of ice crystals. These ice crystals are
hexagonal prisms that form when snow freezes up. Prisms are formed due
to the molecular structure of water. As these ice crystals are formed,
they come down in one of the following forms:
Snow crystals --
Individual, single ice crystals, often with six-fold symmetrical
shapes. These grow directly from condensing water vapour in the air,
usually around a nucleus of dust or some other foreign material.
Typical sizes range from microscopic to at most a few millimetres in
Collections of snow crystals, loosely bound together into a
puff-ball. These can grow to large sizes (up to about 10 cm across
in some cases) when the snow is especially wet and sticky. A
snowflake consists of up to 100 snow crystals clumped together.
Rime -- Super cooled
tiny water droplets (typically in a fog), that quickly freeze onto
whatever they hit. An example of this is the small droplets of rime
on large snow crystals.
Graupel -- Loose
collections of frozen water droplets, sometimes called "soft hail."
Hail -- Large, solid
chunks of ice.
Powder is freshly fallen, untouched, soft
snow. Powder, tiny flakes and crystals form the smooth and soft surface
Most snowboarders and skiers find powder the ultimate surface especially
since it is the best snow to land on because it does not hurt as much as
hard, compact snow.
Crud is the next phase from powder. As more
and more people and traffic move through the powder, the snow gets piled
at certain places and packed down at others. Fresh powder snow soon
becomes "tracked out" and results in an uneven surface with lumps of
soft powder-like snow and slippery patches
windblown snow crust
As the name implies, this type of snow has a
harder crust on top of softer powder snow. Crust is formed when the
sun's rays and the wind melt the top layer of powder, and then the cold
air temperature makes it freeze into solid again.
When the air temperature becomes warmer than
the freezing point, the snow starts to melt and its water content
becomes very high. With this, the delicate snow crystals change into
large grains of ice and slush is formed. Slush is basically snow that is
starting to melt and thus becomes further wet.
This type of snow is the exact opposite of
powder - hard and slippery. Actually, you'll never find real ice
mountain and hill slopes. What you do encounter is snow that has been
melted and frozen again for a number of times. This forms a solid
surface of icy compact snow that is often referred to as "ice".
When modelling snow, it
is essential to decide on what conditions you are trying for. Is it
windblown powder snow which has drifted, conditions where snow still
sticks to vertical surfaces or wetter snow that has fallen in large
flakes? Has the snow begun to melt or is it still very cold?
The Bratton Fleming
model aims at reproducing a fall from the previous night which is
beginning to thaw.
As usual, reference to
photographs is most important. Issues like how snow will fall from
un-insulated roofs and how snow looks like after being swept or
shovelled and walked on.
A good reference from
British snow (rarely heavy) can be found on the website of railway
Roger Dimmick. I find it essential to ensure that the 'snow'
stays where it is intended as some of the materials used, (fine ground
plastic or microballoon) can find itself in every mechanism you own.
This comes in large
containers and is a very good colour. The grain size is, however too
large, but the material is good for building up layers. This I do using
PVA painted accurately on to the surfaces where snow is required and
then carefully sprinkling on the material. If the job is done over a
clean sheet of paper, excess can be reused. The 'snowfall' can then be
wetted using a mister with detergent added and the whole lot fixed by
dropping on dilute PVA.
with the hip roof completed, the first
coats of Woodland Scenics 'snow' is added
one of the best 'secret weapons' . This is 600 micron glass balloons and
is used in the composite aircraft industry to mix with resins to produce
lightweight filler. A good source in the UK is
Aircraft who will sell you 1/2 kilo (that is a lot) for about £9. A
lot cheaper to buy it from here! This material is then sifted on to the
wet Woodland Scenics snow. Detail can be added at this time using small
soft brushed to push the 'snow' around, mimicking, for instance,
slippage on a pitched roof.
If the microballoon
become completely wetted with PVA it will dry more like slush ice and is
an excellent way to model where people have walked through the snow.
Microballon can also be
used for modelling frost with great effect.
The snow is then
finished off using materials supplied by
Deluxe Materials who supply a variety of different snow
types which includes a very fine glitter which if used well will
perfectly simulate sunlight reflecting on snow crystals.
the completed snow application using
microballoon. - click on
image to enlarge
Once the PVA has set,
the snow can be fixed using artist's fixative. I must say however, that
the result is delicate and cannot stand touching. Producing a realistic
snow finish is not quick either. It took over four hours to treat the
station building shown above.
Modelmates supply large aerosol cans of very realistic snow.
This is about as good as it gets for trees, the direction and force of
the spraying determining the snow finish required. The material does
remain soft, so again, needs very careful handling.
Shake the can for at
least one minute before use (and often while spraying). The can has to
be warm to work effectively. A ball inside the can should rattle when
the can is shaken. If the ball does not rattle, warm the can in your
hands for about 5 minutes and then shake it vigorously. Keep doing this
until you hear the ball and the can feels warm. The spray will come out
very fast if the nozzle is fully depressed. As it hardens it will crack
a little, just like real snow. When through spraying, invert can and
spray for about one second to remove excess snow from nozzle. Should the
nozzle become blocked, remove it, place it in boiling water for a few
minutes and it will clear. Wash hands after use. To remove from smooth
surfaces, first scrape off any areas of large build-up, then rub with a
clean cloth (furniture polish also helps to remove snow).
The three main methods of application are:-
1) Even Application Of Snow:
Hold the can in an upright position approx. 300mm from the model. Press
the nozzle very, very gently and fine snow will appear. Move the can
across the model (or a part of the model) in one smooth motion.
2) Very Light Dusting Of Snow:
Hold the can in an upright position with the nozzle very close to the
model, perhaps a tree or shrub. Press the nozzle very, very gently and
fine snow will appear. Practise first before doing this. If you press
gently enough only a very small amount of snow will be sprayed, just a
3) Dense Application:
Hold the can in an upright position very close to the model. It
important to press the nozzle gently at first, then gradually apply more
pressure until you create the effect you are after. We make great snow
drifts this way.
Alternately, simply point the nozzle as close or far from an object as
you wish and press light or hard to achieve the effect you are after.
Never press the nozzle too hard - it comes out really fast.