BODY CASTING ALGINATE
HOW TO USE ALGINATE FOR MOULDMAKING
Mix - without lumps - the alginatepowder into clean water by means of a mechanical stirring device or a kitchen mixer. Watertemperature : 20ºC. After 5 - 7 minutes the gelification process will start. In case the gelification starts to fast the water you are using can be too hard or the temperature can be too high. Lower the watertemperature or use desalted/demineralised water . The lower the watertemperature the slower the gelification will take place. Note : too cold water is unpleasant for the 'victim' who's bodypart(s) will be immersed in the alginate.
CHANGING THE MIXING RATIO :
10 gr. powder on 20 - 30 gr. water
This is the normal mixing ratio.
The mixed product is thick flowing and jelly or puddinglike and perfect to be poured into a bucket or box followed by immersion of the bodypart into it.
For facial moulds : use more powder to decrease the flow of the mixed liquid. Before gelification takes place the liquid has to be kept in place by gently wiping it back to the desired location ( when it flows into clothing or hair : no problem, it is a seaweed based product - completely harmless to the skin or fabrics - and can easily be removed by wetting or washing out in water.)
SEVERAL LAYERS :
Are possible ; a new layer sticks to a previous one as long as the previous layer is not older than 1 - 2 hours.
SHRINK :
Alginaterubber doesn't shrink during gelification. Castings have exactly the same size as the original.
Alginate moulds cannot be stored for a long time : they loose water, start shrinking and tend to rotten after a few days. Store them under water if necessary.
In general alginate moulds are intended for one-time usage.
Starting from the casting made in the alginate-mould a final mould can be made in silicone-rubber which will last for several years and can be reused as often as wanted.
SKIN-FRIENDLY :
Alginaterubber is a natural product based on seaweed and completely harmless for the skin. It can be used on any bodypart without risks of allergic reactions of what so ever. It is only intended for external use ( not in the mouth ).
CASTINGS :
Castings in alginate moulds are possible with concrete, gyps / plaster, polyesterresins, epoxyresins, waxes with a melting point lower than 100°C.
Not with polyurethane resins or polyurethane foams as the water in the alginate mould is an inhibitor for the polyurethane polymerisationreaction.
HOW TO PROCEED / GENERAL RULES :
Slightly grease body / bodypart with a thin vaseline film. This is necessary to copy all details (pores etc..)
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Hairy bodyparts : grease with more vaseline to stick the hairs to the skin: this is necessary to prevent air being entrapped inside the hair ; this tends to give faults in the mould and later in the casting. |
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In case of a facial mould :
Head : cover the hair with PE kitchenfoil from the forehead to the lower part of the neck. Keep the ears free.
Long beards, moustaches etc... can not be copied with alginate.
Keep the openings in the nose free or use small plastic tubes to allow the model ('victim') to breath while the mould is made.
Use a rather thick, syrup-like alginate mixture on the face and build it up in several consecutive layers to a thickness of 8 - 10 mm on ALL parts. The alginate subject to running down from 'high' points (nose , ears,...) has to be replaced as long as the gelification hasn't started.
After gelification : make a gyps/plaster reinforcingmask on top of the alginatemask using plasterbandages (available at www.obeeliks.com). Build up this mask in 3 to 4 consecutive layers and take minute care as to push away all the air between the alginate and the plasterbandages. Wet the plaster bandages with a spray (used for plants and gardening) instead of soaking them in a bucket of water. Too much water lenghtens the hardening of the plasterbandages unneccesarily.
When both masks are ready ; remove them both at the same time while putting your model up straight . Ask your model to move his/her nose and lips to simplify the release of the mask.
Remove the plastic tubes, close of the remaining opening with clay or putty and put the mould in towel to start the casting.
An experienced mouldmaker can make an alginatemould of a face in +- 20 minutes. |
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In case of a hand / feet / arm mould :
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Use a bucket or a PVC tube or a wooden box cut from top to bottom at both sides.
Close it down with tape .
The open end of a tube can be glued to a wooden plate or ceramic tile with silicone or heavy tack tape
The alginatemixture can be much more fluid for these type of moulds.
Pour the mixture in the bucket / tube and let the model put his/her hand / foot etc... in it. Move toes, fingers to let all entrapped air escape. Then wait patiently till the alginate has gelified.
Once this has happened (usally after 10 - 15 minutes ) inject some water with a plastic syringe (without needle !) between the gelified alginate and the bodypart, take away the tape that keeps the tubeparts of bucketparts together and let your model remove his/her hand/foot very slowly from the mould. The injected water prevents the mould from sucking a vacuum - and getting damaged - while the bodypart is removed out of it.
Empty the mould (upside down to let the injected water run out) and the mould is ready to make a cast.
Have fun !
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