Example; concrete hand.
1. Find the join line from which two halves can be separated with no undercuts. Keraforce is rigid, and no undercuts are possible.
2. Fill in any undercuts with Plasticast.
3. Stretchwrap the model.
4. Mix some Insulag, quite soft and place it on a sheet of plastic.
5. Push the model firmly into the Insulag and bring the Insulag up to just below the join line.
6. Take out the model, unwrap it and place it back in the Insulag cradle.
7. Trim any Insulag which is above the join line.
8. Smear Plasticine, modelling clay, sculptors wax, clay or similar material over the Insulag to bring the surface exactly up to the join line.
9. Use a credit card cut square to check that there are no undercuts.
10. Extend the plasticine about 40mm around the model.
11. Make it smooth and flat.
12. Make locating mounds on the flange.
13. Lubricate all the surface of the plasticine.
14. Push drinking straws into the plasticine to make bolt holes.
15. Fit a base plate parallel to the casting open surface. Use plastic or something slightly flexible.
16. Fit another plank on the open cast surface, also parallel. The plates will form flanges to support the mould level while the second half of the mould is made. They must therefore extend
beyond the highest point of the mould, to equal heights.
17. Make wedges of plasticine at intervals on the outside of the flange, for levering later with a screwdriver.
18. Build up shallow walls on the perimeter of the flange, also using plasticine.
19. Cut strips of Biotextile, SBP membrane or cloth to laminate with. Make narrow ones for around the bolt holes, and some broad ones for the base plank.
20. Make two bowls of slurry; For gel coat; 680g Reforce powder and 420g Reinite binder.
21. For laminating; 550g Reforce powder and 450g Reinite binder.
22. Smear the whole surface with gelcoat, being careful not to trap any bubbles.
23. Pull strips of textile through the laminating slurry, wipe the excess off, and place onto the surface.
24. Two strips thick is enough over the model, one in each direction.
25. Make the flanges about 4 strips thick.
26. Add the final 2 layers using stitch bonded fibreglass mat dipped in the laminating solution. Air bubbles at this point are not a problem. The fibreglass is less flexible than the geotextile,but stiffer.
27. Make struts of folded double textile to support the end plates. The end plates must protrude enough for the half mould to stand on them while doing the next half.
28. Leave for 4 hours to set. It should be hard but still trimable with a sharp knife.
29. Separate from the Insulag support, which can be discarded.
30. Remove the model.
31. Clean the plasticine from the Keraforce.
32. Replace the model.
33. Repeat steps 13 to 29 for the other half.
34. Grind the bolt hole ends flat if necessary.
35. Lubricate the mould.
36. Fit bolts and nuts.
37. Stand the mould upright.
38. Mix the casting compound and pour it into the mould.
39. After it has set, strip the casting, clean the mould, making sure the flanges are also clean.
40. Lubricate, assemble and cast again. Castings should be removed when set, and it is preferable to leave the moulds empty overnight.
MAKING A COPY OF A REAL HAND
- Dip hand in molten investment casting wax.
- Dip hand in ice water bucket.
- Dry hand.
- Repeat dip, dip, dry until a decent layer is built up.
- Wriggle your hand free. The fingernails are difficult to free.
- Place the wax shell in a bucket of sand.
- Mix equal weight parts of Reforce 90 and Reinite binder.
- Pour this into the wax shell*
- Leave overnight to set.
- Remove wax shell, either by chipping it, cold, or by melting the wax. Use a blowtorch or hair dryer to get the last skin of wax off.
- Cool and dry the model hand.
- Melt some Multimould Green in a microwave oven in a Pyrex or ceramic bowl.
- Pour it into a deeper container.
- Dip the model hand into it, then into ice water, dry it, dip it etc until a skin of 4mm is obtained.
- Allow the Multimould to cool to ambient temperature.
- Paint a thin coat of Multimould oil onto the skin.
- Strip it by turning it inside out.
- Turn it the right way round.
- Place the Multimould skin in a bucket of Hollofill. *It helps to suspend a stick in it for later handling
- Mix Reforce 90 and Reinite Binder in 60:40 or 50:50 weight parts. Add pigment?
- Pour into the Multimould skin.
- Stand overnight, paint with Multimould oil and invert it.
Several other materials can be substituted for step 20. Some of these are:
Keratab Ultrafine: Brilliant white.
Kerapump 10: Brown with black streaks.
Zambezi Black: Pitch Black.
Plasticast: Easily colored, less brittle than above.
Marmould: Soft elastic fleshy feel, translucent.
Elasticast: Heavy and grey.
Keraset: Very hard, grey.