Are you casting in gypsum based cement either professionally or as a hobbyist?
You have most likely been been using plain plaster of Paris or more solid products such Hydrostone, Hydrocal or even the very strong Forton MG.
All these products have their advantages and particular utilisation. You are probably aware that Forton MG is by far the more robust of all casting products. It has indeed become the defacto standard in the molding and casting industry. This fantastic product allows artists, builder and designers to make solid, durable and lightweight sculptures and moldings.
All good...BUT...Forton is is very expensive.
Specifically in the body casting business, artists and sculptors have 3 main sources of expenses: alginate or other impression material, casting material and marketing.
In the course of my practice at Bodyscape studio have therefore been looking at better ways to do things as It is important to keep these costs under control without compromising on quality. I have perfected a casting mixture that is much cheaper, almost as robust and in many ways, simpler to implement than Forton.
While diluting PVA glue in water as a sealant for some of my pieces, it occurred to me that if I was using this mixture to soak plaster I could obtain a casting material with different qualities.
Being 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 50% PVA glue 50% water per volume, Soak in that volume two volumes of Hydrostone. I mix it for 5 minutes. You will quickly obtain a smooth slurry with no lumps.The mixture has a pot life of 5 minute which is plenty to apply a first layer in a big mold.
Another pot can be mixed and used straight awy on top of the first layer. It is much creamier and stickier than most other casting systems and is a real pleasure to use.
You will obtain castings a very high quality. No air bubbles, no cracks or running marks often resulting from using liquid materials.
The mixture is very heavy and ca be used to easily apply a thick layer on walls and and undercuts.
The casting, which can be reinforced with fiberglass, can be removed from the mold in less than 20 minutes·and will fully cure in a day or two. It will not mark or scartch the way most gypsum based system will.
This is where my recipe really out-performs Forton. A 30kg Forton Kit will cost about $500 in NZ.
To make the same amount of my recipe I only have to buy 25Kg of standard gypsum cement and 5 litres of PVA glue
There is no need for an accelerant and everything only costs me $146. My recipe turns out to be 60 to 70% more economical than Forton without compromising the quality and robustness of your end product. .
It will positively affects your operation.
Most Sculptors will see some other utilisation for this product.
Making shell molds around silicon rubber mould can now be much thinner, lighter and stronger than standard plaster and can be build much faster...
The formula is not recommended for smaller hollow sculpture. It is not runny enough to be slushed out of a mold and is too thick to be poured inside a narrow opening .
Modern PVA glues are weather resistant. However, I would still use modified Forton for pieces to be permanently displayed outside.
You will like it.
About the author.
Olivier Duhamel is a sculptor based in NZ and specialising in bronze figurines. His Bodyscape studio publishes the Famous “Boobs casting manual”
His bronze sculptures and nude pencil drawings can be seen on www.duhamel.bz and in art galleries in New Zealand, Australia, France, Belgium and China. This article can be reproduced freely on the condition that it is not modified and that this last paragraph is included along with the external links.
Karen on June 16, 2014:
I'm looking for light but tough plaster of paris alternative to use for small silicone moulds (as a hobbyist); any suggestions/advice please?
Suze on June 08, 2014:
Thank you so much!