For our first seminar/demonstration we looked into creating forms with plaster and reproducing it in thermoplastic on the vacuum former. The theme for our projects is WW1, thus the form being a WW1 style military helmet.
To start we were shown how to make the moulding device to create the plaster form.
1) Make a base with a swivelling pole in middle.
2) Once you know the design you are reproducing into three dimensional forms, draw a side view pattern, ensuring measurements and proportions are all accurate to the real, original design.
3) Draw a cross section of your side view design, stick on strong plastic and cut out with a Stanley
4) Stick well to pole on base so that bottom of stencil is centred and in line with the surface of the base. (You may have to deduct a cm or half from the side of the stencil stuck to the pole to ensure you keep the right proportions).
5) Make plaster: fill plaster bowl half way up with water (warm) add plaster powder till “hill like” forms reach the surface and then mix to an even consistency with your hand.
6) After mixing and leaving for a while, the plaster mixture should be thick enough to place on base and you can start circling the moulding device you made earlier to produce the equal and proportional design.
NOTES:
* Try to work quick, the plaster will start hardening if you are unprepared and slow.
* You will need to cover your work place with newspaper, so easier to clean up after and to protect work surfaces.
* Use protective goggles, apron and a mask when using plaster to prevent breathing in powder. Plaster is safe once wet and hardened.
* It is safest to have hair tied up and jewellery tucked in or off during plastering, the vacuum forming and the ban saw process.
Once the plaster form is hardened we continued the process to vacuum forming.
* Before vacuum forming remember to spray your mould with releasing agent so it is easier to separate your plaster mould from the cooled plastic.
1) With your mould in place on a base and in the vacuum former you select a large piece of thermoplastic to place and lock above your mould and heat up until the plastic is visibly durable. This is when you pull the lever on the vacuum former to push your mould upwards and into the mould.
2) Whilst thermoplastic is still hot press the vacuum on. This should suck all the air out and compress the durable plastic up against all the edges and surfaces of your mold.
3) When plastic has cooled (when you can no longer indent it with your finger nail, lift out of vacuum former and separate from mould.
4) Next you will need to cut the shape out with a plastic ban saw, you may also want to file edges to get rid of any rough and sharp pieces.
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