Making a Flexible Mold and Mother Mold
Mold Making : Brush-On Rubber Mold of a Bust using Smooth-On Urethane Rubber (Brush-On 40)
http://www.youtube.com/watch?v=sOyBawt1-Ec
PART I
1. Apply Universal Release to all surfaces including base
PART II
4. Mix Urethane Rubber: Brush-On 40 – Measure A and B in equal amounts
5. Mix urethane rubber: you’ll add colored pigment to layers 2 and 4
6. APPLYING URETHANE RUBBER
First layer is the “detail coat”; apply thinly; push urethane rubber into detail
Mix and apply more materials as needed
7. Allow urethane rubber to gel till tacky 30-40 mins at 72 degrees. Should be TACKY: sticky to touch but doesn’t come off model
8. Mix and apply second layer… no color
9. Allow urethane rubber to gel till tacky 30-40 mins at 72 degrees ~ can thicken with shredded black tire rubber
Add shredded black tire rubber to thicken urethane rubber to make parting “shims”; paint it from top back of head down to bottom of model and to outer rim of base; paint a line around the model’s base about 1 ½” from the model. This is a Registration Key.
Use this thickened urethane rubber in undercuts and indentations
Use this thickened rubber to create Registration Keys along base
11. Mix and apply third layer of urethane rubber (color added)
12. Allow rubber to gel till tacky 30-40 mins at 72 degrees.
13. Build up parting shims and undercuts using one more batch of urethane rubber
14. Apply fourth coat (no color)
15. Let all layers cure overnight at room temp
PART III
16. Applying the support shell = “Mother Mold”
Draw parting lines : divide model into 3 sections
Use modeling clay to make support for parting shims
Apply clay supports to other side
Fill in open spaces and smooth clay pieces together
Complete clay shim around model
Apply clay supports all around to back of shims
Carve registration keys into clay
Apply wax over shims, model, base
Apply Universal Mold release over shims, model, base
Mix Plaster FGR
Apply a ½” layer evenly to mold rubber including base
Remove shims
Use this clay to make the 2nd parting shim : defines 2nd and 3rd shell segments
Apply clay supports to other side
Fill in open spaces and smooth clay pieces together
Carve registration keys into clay
Apply wax over shims, model, base
Apply Universal Mold release over shims, model, base
Mix Plaster FGR
Apply a ½” layer evenly to mold rubber including base
Remove shims… no shims are necessary for the third section
Apply wax over model, base
Apply Universal Mold release over model, base
Mix Plaster FGR
Apply a ½” layer evenly to mold rubber including base
PART IV
17. Demolding: remove shell segments
Can use chisel or screw drivers or wood shims to open up shell
Use X-acto knife to cut mold from bottom up along thickened seam in rear of head
Get another pair of hands to help with this
Gently pull mold away from model
PART V
18. To Cast
Apply Universal Release to all surfaces
Seat mold in shell; make sure seam is aligned
Secure mold with stretchy inner tubes
Mix and pour ingredients of your choice into mold cavity, being conscientious about its properties:
viscosity, drying time, safety, measuring
Rotational cast or solid cast material
Let it cure for required amount of time
PART VI
19. Demolding:
Remove straps, mother mold, have a look
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