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The Go-Wax technique,
an innovative method for body casting mother molds.
By Olivier Duhamel
This method is a vast improvement on the
traditional methods for building a mother mold. Most life casters use
either plaster gauze bandages or other fabric dipped in fast setting
plaster. True and proven methods for sure but read on….
…what if you could build a mother mold that is:
much lighter that any kind of plaster. (does
not put too much pressure of soft tissues and makes it more
comfortable for the model.)
much stronger than plaster bandages, (No
distortion when removing the mold or laying it down.)
much faster to apply. (It is long and difficult
to painstakingly apply plaster gauzes or cheese cloth against the
alginate. Cut this time in half…)
is ready to remove from the model almost a soon
as finished. (no need to wait for plaster to set.)
requires no preparation time or effort. (no
need to pre-cut lengths of bandages or cheese cloth, mix plaster etc…)
adheres perfectly to the alginate skin, (No
gaps between alginate and mother mold means no dimples or ripples in
the final casting, even where the alginate skin is too thin.)
is extremely cheap. (are we not tired of
throwing away plaster gauzes molds and filling up landfills with our
cash?)
is perfectly safe, organic, non toxic,
recyclable and everything friendly. ( and no animals have been harmed
either…)
Can you guess? Interested to know more? Read on...
This article is an extract of Bodyscape's
Body Casting Manual. It describes an
innovative method of constructing the mother mold using wax.
A much better way
Using plaster bandages is the most commonly used technique to build a
rigid mother mold over the flexible alginate skin. The cheese cloth and
fast setting plaster is an improvement on the plaster gauze technique.
There is however a much better way to construct this mother mold, using
wax instead of plaster. This method is particularly suited to
professional life casters as it requires some additional equipment which
would be an unnecessary expense for a one-off project.
Principle
The basic principle remains the same. You first apply alginate on the
model’s skin and embed cotton wool in the alginate before it sets as you
would normally do.
You then paint molten wax over the alginate. Being
liquid, the wax will perfectly cover all anfractuosities of the
alginate.
More wax is painted over and reinforcing fiber
glass applied until a layer of about 2 or 3 mm (1/10 in) has been build.
Once the wax has cooled down you can release the mold as you would
normally do with a plaster shell. The cooling down of the wax can be
accelerated with cold water applied with a sponge or sprayed on. You
will find this being much quicker than any plaster based method.
Tools and equipment
You will need some additional tools and equipments over what you
normally use:
an electric frying pan or a crock pot equipped
with a thermostat,
a thermometer,
an old saucepan,
a large paintbrush and a small paint brush,
a block of about 2.5 kg ( 5lb) of paraffin wax,
fibreglass mesh.
What kind of wax to use?
Any kind of wax would work for the purpose. However there is a risk that
the molten hot wax will splash or drip on the model skin. This is why
you want to use a wax that has a very low melting point. A low
temperature wax will be very comfortable and will cool down quicker than
any other kind of wax allowing for a quick release of the mold.
Paraffin wax is liquid at 40°C (104°F). This is a
temperature that is very comfortable and will not burn. Paraffin wax is
often sold as preserving wax but the cheapest source is candle making
wax sold in most craft stores.
How much wax to use?
Most mold will weight less than 1 kg (2lb) and 2.5 Kg (5 lbs) of
paraffin will be more than enough for the largest castings. Most craft
supplies stores stock candle making paraffin. A 4kg (8lb) slab should
cost you about US$20 You can also buy Polytec’s Poly skin wax
Preparation
You will need to melt it in an old electric frying pan equipped with a
thermostat. Paraffin will melt at very low temperature. You want to find
the thermostat position that will keep the paraffin at 45 °C (113 °F).
At that temperature, it will be liquid enough to be easily painted and
cold enough not to present any danger if accidentally in contact with
the model’s skin or your own.
Cold paraffin wax is brittle. To ensure that the
wax mother mold is strong enough to adequately support the weight of the
alginate and to received the casting material it must be reinforced with
fibreglass.
Pre-cut a number of fibreglass mesh rectangles,
squares and bands of various sizes, enough to cover the casting
area twice.
How to apply the wax?
When you have finished applying the alginate and embedded cotton wool in
it, you are ready to paint the wax mother mold.
Pour half of your wax out of the frying pan into
an old saucepan.
Put on latex gloves and paint the liquid wax over
the alginate, starting from the top. Because the wax is very cold you
can safely overlap the alginate over the model’s skin. You will have
covered the model’s skin with baby oil outside the casting area. Baby
oil will make it easy for the wax to be removed from the skin and will
allow fine hairs to painlessly glide out of the wax.
Use a large paintbrush to quickly cover most of
the alginate and then use a smaller brush to fill smaller
anfractuosities or hard to reach areas.
Once you have made one or two thin layers, you
must apply a layer of reinforcing fiber glass. Pour leftover wax back
into the pan. Dip one rectangle of fibreglass in molten wax and stretch
it over the first layer of wax. Repeat, each piece slightly overlapping
its neighbour. Pay special attention to the edges of the mold. Then
paint some more liquid wax over the fibreglass to embed it in the layer.
This short video clip is my first
attempt at illustrating the process...
Thanks Jill for being such a patient and graceful model.
The music illustrating this video is a Concerto for two violins in D
minor by Johann Sebastian Bach which I bought for USD1.79 from ITunes.
However, this particular recording is apparently licensed
to Sony Music Entertainment. As a result Youtube is blocking the playing
of this media to German viewers. If your IP address is deemed to be
German you will not be able to watch this clip. Austrians and Ethiopians
are most welcome to watch. This has been implemented by people who
received a salary for their wisdom.
What thickness?
The thickness of the wax mold must be right…. If it is too thick it will
take a long time to cool down to the point it becomes rigid and strong
enough for the mold to be safely removed without any risk of opening
itself up under the weight of the alginate. If it is too thin it may not
have enough strength to support the weight of the alginate.
A thickness of 2.5 mm (1/10 in) is the right
balance. At first you will be tempted to build a thick layer, but with
experience you will discovered than a thinner layer properly reinforced
with fibre glass will make a very strong mold indeed.
Once you are satisfied you have build a strong
enough layer of wax over the alginate. You can cool it down by rinsing
it off with cold water by either spraying over or rinsing it with a
sponge.
When to remove the mold?
The mold is ready to be removed from the model almost as soon as you
have finished applying it. If you have built a thick layer of wax, you
will have to wait for it to cool down before releasing the mold. With
practice you will find a thin layer gives sufficient strength, is faster
to build and allows for a quick mold release.
Casting
Casting in the alginate is done in the normal fashion.
Demolding
Demolding presents no particular problem. The wax shell will easily come
off the alginate as cotton wool is not very strong.
Reusable
Once your casting is cured inside the mold. The wax shell can be
separated from the alginate skin and remelt for future use. One of he
advantages of this method is that the wax can be reused for many molds.
Once you have unmolded your casting you simply remelt all the wax. Pick
up the fibreglass mesh rectangles, let excess wax drip and set aside for
future use. Then sieve out all bits of alginate, plaster and cotton
wool.
Full 360 molds
If you are building a full in the round mold, you can easily paint two
half shells and then weld then back together using a hot knife and
painting more molten wax over the weld for a very strong shell. It can
be quickly further reinforced by simply painting more molten wax over
it.
Safety considerations
Wax is very flammable. The temperate above which it will spontaneously
catch fire (flash point) is very low.
To put down a wax fire, never use water. Simply
smother it with a lid or blanket or use a powder extinguisher.
To avoid setting wax on fire in the first place,
never melt it over a direct flame such as a gas burner. Always use
either an electric frying pan or the double boiler method by which the
wax container is melted inside a pot of hot water.
Hot wax may burn the skin. This is why you must
use a wax that melts at low temperature. 45 °C (113 °F). is very
comfortable to the skin. Anything above that will be uncomfortable at
best or will severely burn skin at worst.
With this technique you will be using wax at 45 °C
(113 °F) or less and applying it over the alginate so that it should not
get into contact with you model’s skin other than around the edges of
the alginate skin. If it accidently does splash or drip over your
model’s skin, it’s low temperature will not constitute a hazard. It is a
good idea to reassure your model by having her or him dip one finger in
the molten wax before starting and realise that it does not present any
danger.
Please familiarise yourself with wax working and
the temperature of your particular wax before using it on a live model.
Always check the temperature of your wax pot with a thermometer before
starting as it is possible that the position of the pot’s thermostat has
been accidentally moved up.
As with plaster, any hairs near the casting area
must be either protected or covered in petroleum jelly.
Dress appropriately. Wax is a very good glue that
will stick to anything but water. It will permanently soil any item of
clothing it lands on. Skin being mostly water, wax will easily peel off
the skin.
Conclusion
I have successfully used this method on many molds and find it vastly
superior to any other method. Once you have tried it, I suspect that you
will never use plaster ever again.
Olivier Duhamel - May 2010
About the author. Olivier Duhamel is a New Zealand
sculptor specialising in bronze figurines. 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.
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