Submit a life casting
or bronze casting article article.
by Olivier Duhamel
Professional foundries have a purpose
made furnace to melt the bronze. In this article we will simply
construct a temporary furnace using LPG gas as a fuel. The design
of this furnace has been successfully used over many years to melt
amount of bronze from a couple of Kilos (4lb) and up to 20Kg (40lb) This
article is an extract of Bodyscape "Bronze
Casting Manual" A complete tutorial teaching the lost wax ceramic
shell method through an easily achievable casting project.
Tools and materials
About a square meter of 3cm thick ceramic
refractory blanket (10 square feet, 1 inch thick)
8 firebricks
Scissors
Important considerations
It is important to build an efficient furnace as
the metal must melt as quickly as possible to reduce the risk of
oxidation and to save on fuel.
There are many factors and complex physical
equations to design an optimum furnace. Such considerations are beyond
the scope of this manual and certainly beyond the extent of my
knowledge. I will provide you with simple instructions to build a simple
furnace that will melt bronze in about 25 minutes.
You could spend vast amounts of time and money
building or buying a heavy duty, sophisticated furnace without any
significant gain in efficiency. The advantages of this furnace are:
Extremely cheap
Quick to build
Lightweight, temporary, fold away, portable
Easily adaptable to any size crucible
Works every time
Directions
The furnace must be built outdoors in a space wide
enough to give at least 1.5 metres (5‘) clearance all around it.
The first step is to cut a band of ceramic blanket
twice as wide as your crucible is tall.
Put your crucible on the ground and roll that
length of blanket around it, leaving a space of about 3 cm (1 ¼
“)between the blanket and the crucible.
Cut off excess blanket so that there is only a
small overlap (10cm, 4”).
You have the luxury of being able to custom build
a furnace perfectly adapted to your crucible. As a rule, the walls of
the furnace should be as close as possible to the crucible. Try making
this gap slightly narrower than the diameter of your gas torch. It does
not have to be exact and perfect.
Arrange four fire bricks as shown.
Cut a piece of blanket large enough to cover the
two base bricks.
Cut a hole at the base of the furnace body. The
flame will enter the furnace through this hole which is sometimes called
a tuyere. This hole is slightly smaller than the diameter of your
crucible, eyeball it.
Set the furnace’s body on top of the base.
Cut another square piece of blanket large enough
to cover the top opening. When the furnace is in operation this lid will
only partially cover the furnace, leaving an exhaust vent which can
easily be adjusted by moving the cover back and forth.
The furnace is now ready to be used.
To complete the work area, we must set up the
blowtorch. The hottest part of the flame will have to hit the crucible
inside the furnace. Adjust the position of the torch so that it is level
and aligned in front of the furnace opening and at about 30cm distance
from the crucible (12”) The distance from the torch to the furnace
opening will vary with each torch. (More on this later).
I have used 3 bricks to keep the blowtorch handle
in place. It will be easy to later adjust the distance to the furnace if
needed.
The most important quality of a good furnace is
its ability to keep heat inside. It must be well insulated. Make sure
that your installation is air tight with the exception of the tuyere and
the vent.
The tuning of this furnace is explained in later
section of the manual.
This short video clip illustrates the whole
procedure.
It illustrates the construction of a temporary
furnace as described in the "Bronze Casting Manual". The advantages of
this furnace are that it is quick and easy to build, inexpensive,
reusable, temporary, portable, fold away, adjustable to any size
crucible. It also works very efficiently.
About the author
A New Zealander since 1987, French born Olivier
Duhamel is a sculptor specialising in the female human form and
makes delicately crafted small bronze figurines.
After having been introduced to the fine art of
metal casting by sculptor and founder David Reid, Olivier has set up his
small home foundry and has since cast over 500 pieces using basic tools
and ingredients. He takes pride in the quality of his castings. His
bronze works are sold in art galleries across New Zealand and also in
Australia, China, France and Belgium.
He is also the author of the “Body
Casting Manual” and "Bronze Casting Manual" published on www.bodyscape.net.nz. This article can be reproduced freely on the
condition that it is not modified and that this last paragraph is
included along with all hyperlinks.
Bodyscape
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