Author Topic: Casting plaster rocks on a steep surface  (Read 725 times)

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Bob

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Casting plaster rocks on a steep surface
« on: March 15, 2023, 05:02:51 PM »
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I will shortly try my first large scale attempt at casting plaster rocks on to a styrofoam base.  The slope will be steep, so my question is whether the plaster will adhere sufficiently well, or should I put screws or nails into the styrofoam slope with the heads sticking out some to give the plaster something else to grab hold of?  I will eventually cast rocks to make Maryland Heights (see first page of my Cumberland Subdivision thread) and this will be both steep and large, and I don't want landslides to occur!  Anyone have experience with this?  Thanks!  Bob

wvgca

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Re: Casting plaster rocks on a steep surface
« Reply #1 on: March 15, 2023, 05:18:26 PM »
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best off letting the plaster get 3/4 hard, so that it will still somewhat conform to the surface .. i used this method on my layout eight years ago, and so far it's great

Scottl

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Re: Casting plaster rocks on a steep surface
« Reply #2 on: March 15, 2023, 08:15:17 PM »
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I purposely leave the styrofoam surface rough to help adhesion.  Nails or screws would work too but might be awkward with some molds.

CRL

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Re: Casting plaster rocks on a steep surface
« Reply #3 on: March 15, 2023, 10:47:42 PM »
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Do what the stucco guys do. Apply a scratch coat to the surface.

MetroRedLine

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Re: Casting plaster rocks on a steep surface
« Reply #4 on: March 19, 2023, 10:03:27 PM »
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Cast them outside the layout, then use adhesive caulk to glue them to your styrofoam scenery base. Use sculptamold to fill in any cracks/gaps. Paint everything over with a coating of artist's gesso, then stain/paint as desired.
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