One of the biggest reasons I think soft waxes aren’t more popular for
professional quality wax models is that ideally, the completed wax
model should have a thin cross section, of less than 1 mm thick. In a
wax model the size of an average ring, say, thicker cross sections
just aren’t usually necessary, contribute to porose casting, are a
waste of precious metals, and make for an unnecessarily heavy
While soft waxes can be sculpted into many different shapes easily,
it is the “hollowing out” process of achieving that 1 mm ( or less)
thickness that becomes almost impossible with a soft wax. At this
ideal wall thickness, they just collapse in your fingers. Even
"carvable" injection waxes are difficult to bur, file, or hollow out.
Hard carving waxes carve easily, can take on fabulous detail, can be
repaired invisibly and in seconds with the same wax and a heat
controlled tool. Hollowing out hard carving waxes is done easily with
a strong light behind your work, watching the color of the was
thickness change as you bur out the wax. Carving waxes can also be
worked hot, rather a “syrupy” consistency, but when cooled, they can
be again carved as well as hollowed out unlike softer waxes.
A subtractive method of generating wax models by hand, as well as
machining, can be taken to extreme accuracy and detail, and hollowed
out to the most incredible lightness, making a sophisticated casting
with no extra weight than necessary.