A strong, affordable and easy to use
casting material for body casting artists.
By Olivier Duhamel
In this article I will be discussing the
merits of an affordable alternative to Forton MG as a robust casting
material for life casting and other usage.
Introduction
If you are casting in gypsum either
professionally or as a hobbyist you have probably been using plain
plaster of Paris or more robust gypsum based cements such Hydrostone,
Hydrocal or even the very strong Forton MG casting system.
All these materials have their advantages
and specific usage. Like me, you have probably discovered that Forton MG
is by far the more robust material and it has indeed become the standard
in the body casting and life casting industry allowing artists to make
solid and lightweight pieces.
However Forton is a proprietary casting
system and as such is fairly expensive. Life casting artists have three
main cost centres: alginate, casting material and advertising… Keeping
your cost down without compromising with quality must be high on the
priority list of all professional studios. I have therefore been
experimenting with various alternatives to the expensive Forton system
and have now settled to a casting mix that is much more affordable,
almost as strong and in many respects, easier to use than Forton.
My Formula
I have been using a mixture of PVA glue
diluted in water as a sealant for some of my castings. It occurred to me
that if I was using this mixture to soak plaster I could obtain a
casting material with new properties, always curious to discover better,
cheaper, faster ways to do things, I experimented with plaster of Paris
and with Hydrocal at different mix ratio but have since settled with
Hydrostone.
I mix PVA glue with water to a ratio of
one to one and soak in that volume of liquid a maximum of two volumes of
Hydrostone. I mix it gently by hand and then mechanically for 5 minutes
as one would do for Forton or plain Hydrostone.
It is easy to mix and you will quickly
obtain a smooth paste. I have never had the small lumps that are often
appearing in a Forton mix. All in all it is easier and quicker to mix
than Forton.
The pot life of that slurry is just about
5 minutes…this is more than enough to apply a first layer even in a
large mold. Mixing it with very cold water will slow down your setting
time. A second batch can be mixed and applied immediately. I paint it on
the alginate or silicon mold. It is a real pleasure to work with. It is
much heavier and stickier than anything else I have been using before.
My resulting castings are consistently of
a very high quality with none of these infuriating air bubbles pin
holes, fine cracks or, “runneth” that more liquid casting materials are
often producing. One of the annoying aspect of Forton when casting it an
alginate mold is that it is very runny for almost half an hour, as a
result you often get a very thin first layer specially on the vertical
part of the mold.. That first layer is very fragile and sometimes cracks
when applying the second layer, especially when the alginate skin does
not adhere perfectly to the mother mold. No such problem with this
formula. The mix is much creamier than Forton or plain Hydrostone and
you will easily build a thick layer even against vertical walls or
overhanging parts and undercuts. I have been able to cast an entire
torso in 15 minutes where a similar mold would have taken me over an
hour with Forton. Many times, when fibreglass reinforcing is not
necessary, I have been able to cast in a single layer.
·
Demold time is around two
hours. Like plaster it will warm as it cures and is fully set when it
cools down again. Full strength is achieved after 24 hours and it is
fully cured in a few days depending on ambient humidity.
·
I have not been testing
comparative strength for lack of an appropriate test bench and
methodology. It can obviously be reinforced with fibreglass to increase
resistance to shock like you would normally do with a Forton casting.
·
Simple test show that it will
become as scratch resistant as Forton once it has fully cured.
Cost comparison.
This is where my formula really shines
and completely outperforms Forton MG. 22kg of Forton FGR powder
(modified Hydrocal) and 10kg of VF812 resin will cost me $497 here in
New Zealand. This is including the required amount of accelerator but
excluding any other agent.
To make an equivalent batch of my formula
I only need to buy 22Kg of standard Hydrostone and 5 litres of weather
resistant PVA glue ( I am using Selley’s Aquadhere, in the USA a similar
product is Weldbond.) There is no need for an accelerant and everything
only costs me $146. Weight for weight my formula is therefore more than
70% cheaper than Forton. Since you will probably use slightly more
material than you would with Forton, it is probably only 60% cheaper.
This is still a very significant saving. You can report these savings to
your customers and become more competitive or chose to increase your
margin, In both cases it will positively affects your bottom line
without compromising the quality and robustness of your product.
Other usage.
The astute sculptor will immediately see
some other usage for such a material. If you are building mother molds
around silicon rubber or urethane mold, this recipe will allow you to
build thinner, lighter and stronger mother molds much faster than by
using standard plaster of Paris and much cheaper and much quicker than
by using Forton.
It is probably not suitable for small
size hollow casting as it is too sticky to be slushed out of a mold. It
is also too thick to be poured inside a narrow mold. But it can be made
runnier by reducing the mix ratio to 1 to 1.5 instead of 1 to 2.
Even though modern PVA glues are often
advertised as waterproof or weather resistant, I would still use a
properly modified Forton slurry for works designed for permanent outdoor
display. For all other applications, you will find it really easy to
apply on the inside of an open mold, It does not run the side of the
walls and can be pushed in small places like fingers or nipples.
Do try it… You will love it. I am no
longer using Forton but for the largest job where weight is and issue.
Forton MG is a registered trademark of
Forton BV, The Netherlands. Hydrocal, Hydrostone are registered
trademark of USG corporation.
Olivier Duhamel - July 2009
About the author.
Olivier Duhamel is a New Zealand sculptor specialising in bronze
figurines. He is also the name behind the Bodyscape life casting studio
and the author of the very respectable “Boobs 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.. |
Bodyscape
