Tutorial:
1/ Sclupting positive wall
Scultp a large wall section within polystyrene to your liking.
Make sure the final result is not too much regular. I pressed some stones to ensure the wall surface is not regular as an example.
Do not hesitate to exagerate sculpting as with any positive mold.
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2/ Making a negative (1)
Apply lubricant to the wall so that milliput will not stick to the positive.
Make sure NOT to use oil-based lubricant since that would cause a chemical reaction with polystyrene ruining your wall.
Get some wood surface and cut it several time with a modeling cisor; this will help milliput to stick hard to the wood.
Prepare your milliput so that it is very flexible (use water!). Apply a layer of milliput over the wood and press it hard to a 3mm-thick regular surface.
Now press your milliput onto the positive wall VERY hard (about 60-70kg pression) and wait for an hour for the milliput to start curing.
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3/ Making a negative (2)
Separate gently the positive wall from the milliput and its wooden base. If you used lubricant properly that should be fairly easy and the milliput shall not remain sticked to the positive.
Way a day for the milliput to cure.
With modeling cisor remove any excess milliput to have a clean negative wall.
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4/ Engraving foam (1)
Cut wall from polystyrene to desired dimension.
I'm using 12x4cm sections.
Press cut sections with negative milliput wall. Press HARD. I mean VERY HARD. I do jump lay foam on the floor, lay negative milliput wall atop, and jump on top of it a couple of time. Wathever your technique, make sure to apply even pression on the foam, since uneven pression will wrap it forever. Do the same on the other side of the foam.
For a perfect result you could use two negative wall to engrave both sides the same time. If using a single negative, the 1st engraved side will loose some of its depth when working the second side.
Please mind that this pression will cause the foam to thin from 10% to 30%. Do some test with your own foam.
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4/ Engraving foam (2)
Now use the same technique to engrave the wall top. Do that gently and make sure not to press as hard as for the wall sides since that would wrap you wall forever.
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5/ Sculpt
Use the same technic with thiner and smaller foam sections that will be used to build crenels.
When engraved, cut and bevel them to crenel shape.
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6/ Assembly
Use your favorite foam-friendly glue to finish your wall section.
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7/ Done!
Now your have your walls ready for painting and basing.
Make sure NOT to prime them using aerosol-based primer since that would dissolve your foam...
With this technique I build a single wall section every 10 minutes.
You can use the same technique for towers and gateway. For towers, you will have better results by cutting 4 sides, engraving them, embeveling them and glue to the final tower.
