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Rock castings
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 Posted: Sat May 14th, 2011 09:15 am
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Joined: Tue Jan 24th, 2006
Location: Berwick, Australia
Posts: 2403
I have started work on the rocks for the layout, firstly spent a couple of days making castings.

A good friend has been instructing me on his method, and has let me use his molds.

The molds are home made using latex and the castings are kinda hollow.

Plaster  is about 1/2 inch thick. The weight of this section is about 40 kgs ( 90 lbs ) and estimate the total for the layout will be 260 kgs ( 470 lbs) The castings are all made using casting plaster which gives about 10 minutes working time

The castings vary in size from 6 x 6 to 34 x 15 inches. to give you some idea how large this first section is it is 6 foot high and 3 foot six wide.

The castings have lots of fine detail so when the painting is done the detail will POP.

Don McL
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 Posted: Sat May 14th, 2011 01:00 pm
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Joined: Fri Apr 8th, 2011
Location: Dallas, Georgia USA
Posts: 35
I used to cast all our Rock from plaster until we had slight problem with a section on benchwork. It cracked the main facia boards from flexing. So I ended up switching over to a more forgiving material and could still use the same molds.

Expanding Urethane Insulation Foam, the type used to seal gaps around your home.

It is so easy and lightweight it was not funny. And since the mold surface dictates the "skin" side of the casting the detail is still there. Plus you can cut it with a razor knife. Priming and Painting is slightly different technique, but for large sections it really was easier to carry a 2 pound section that was 23" x 49" - Floor to Table section.

Just an idea for ya. Something that worked for us.

Last edited on Sat May 14th, 2011 01:03 pm by Nn3Designs

Just when you thought they idiot proofed the world, someone builds a better idiot.
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 Posted: Sat May 14th, 2011 07:36 pm
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W C Greene

Joined: Fri May 4th, 2007
Location: Royse City, Texas USA
Posts: 8183
Good looking rocks, Don. I have used the expanding foam also and it seems to work fine, much less weight and less prone to cracking than plaster. Of course, I have to use lightweight and durable stuff for my scenery.


It doesn't matter if you win or lose, its' how you rig the game.
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