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Nieuw Forum
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The making of a piece of jewelry
with the lost wax method.
It is called so
because the wax model is burned away when the mold is created. The making of a metal Atlantis Ring today is just like small metal objects were made in ancient times. Of course today the materials are better, but the principle is still the same. History of jewelry making compared
with modern techniques.
In the past beeswax was used to make the desired object.
Today we have many different kinds of wax. It can be hard wax, soft wax, sticky,
shrinking or non-shrinking. In the past clay was taken from the shore of a
river. The wax object was embedded in the clay with a hole left open. Today the
wax object is embedded in a special heat resisting kind of plaster called
investment powder. The powder is mixed with water and poured in a cylinder that
holds the wax model. In order to get air-bubbles out of the mixture it is put
under vacuum. The cylinder with the still liquid plaster is placed under a bell
jar and the air is removed by means of a vacuum pump. The air is let back in and
the investment now has no more air bubbles that would become small metal balls
on the object once the molten metal goes in. In the past the dried clay with the
wax inside was put on a charcoal fire. Air was blown onto the fire and the clay
baked until hard. At the same time the wax burned away and the mold was created.
You know how water
stays in a bucket when you swing it around, and that principle was used in the
next method. The cylinder with the molten metal in the opening was attached to a
2-meter chain. When the metal was hot enough it was swung around in a circle as
fast as possible so that the centrifugal force pushed the metal in the mold. You
can imagine how risky those two methods were. Based upon the idea of centrifugal
force a dentist some 70 years ago invented a spring driven casting machine. The
cylinder is placed on a horizontal arm that is attached to a wound-up spring.
The crucible with a hole in the side is placed with the opening against the
cylinder. The metal in the crucible is heated to liquidus and the spring
released. The arm turns very fast and the liquid metal is thrown in the cylinder
with considerable force. The newest method is based upon the fact that the solid
investment is porous and air can pass through. The cylindrical mold coming out
of the oven is placed on a suction hole that creates a vacuum under it. Air
flows from the opening in the top through the mold and when the liquid metal is
poured into the top hole, it flows in every small recess of the mold. Once the
metal is in the mold, it is allowed to cool a little and then the mold is
quenched in water. The investment powder broken away and the object, ring or
whatever is cleaned. The sprue is cut of and the piece filed, sanded and
polished.
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Today the hardened investment with the wax model inside goes into an oven. The
wax is burned out and the mold is ready to receive molten metal. In the old days
the metal was melted by blowing lots of air towards the fire that held a clay
crucible with the metal in it and once liquid, it was poured in the clay mold.
The clay was then broken and the object released. Today we heat the metal with a
torch that burns gas and oxygen, and the pouring of the metal into the mold has
been very much sophisticated. Because liquid metal has a viscosity that
resembles treacle, it is so thick that it will not flow easily into every recess
of more or less intricate designs. Therefore different methods have been
developed to force the molten metal down into the mold. The channel towards the
object inside the mold is called a sprue and has to be wide enough to let the
metal flow through fast enough. Not too wide so that it becomes difficult to cut
it from the object later. Many thin sprues are better than one thick one.
