Making Rock Molds

[Chopps118]

Hi All, I have been thinking about making my own rock molds. I have some very nice limestone rock formations here where I live. The only thing is I just don't know what to use to make them. Can someone point me in the right direction.
Thanks

 

[Railrunner130]

http://www.cccrow.com/

There are a bunch of how-tos there that will aim you in the right direction.

Also, Woodland Scenics makes a variety of molds with directions on how to build the rocks.

 

[waltr]

Latex is typically used to make a mold.

Try googling: "making rock molds" for lot of info.

 

[Iron Horseman]

Hi All, I have been thinking about making my own rock molds. I have some very nice limestone rock formations here where I live. The only thing is I just don't know what to use to make them.

Do you mean you want to know how to make the actual mold itself, or what to use to simulate the limestone rock?

The others are talking about mold material.

For a model of limestone it would depend on the limestone formations you are familiar with. There are about as many types of limestone outcroppings as there are freight cars. Here in Kansas the limestone is in 3" to 12" layers with chalk or shale between them making a very banded look. For that I would use old broken up fiber-glass roofing tiles for the chalk and shale sandwiched between carved Linoleum.

Other places I've seen much more blocky limestone formations. For that I think I would make my own "limestone" with aluminum foil. Make a plaster "Master" then make the latex mold off of that.

 

[Chopps118]

Thanks everyone lots of good advice. My plan to is go looking around in the hills. I went to a craft store the other day and picked up latex, boy it stinks.There are a few rocks here by the house that I'll first then go out to the hills.

 

[Trussrod]

Hi Chopps,
Ya, I think that's the Amonia in it. Stir it up good by hand, I think that should help to kill some of the odor.

When you find a rock or rocks you want to make molds of brush any loose dirt of it, at least the area you want to mold. You can also spray the surface with a mold release but I think possibly a Silicon spray would work good or even possibly a cooking spray to help prevent the latex from sticking to the rock surface.

I haven't used any before myself but might try some in the future depending on how many crevices the rock has?

Usually molds are not made too deep so they can be applied to hillsides once the Hydrocal/casting plaster just starts to, where it doesn't look slick on the upper surface and make sure it doesn't tend to run when you go to lift it.

Also be sure to use something like an acid brush to poke/push the plaster into all the various creavaces of your mold. I prefer to only use about two layers thick of laytex on the rock to give me a more flexible mold that will easily conform to my hillside and even wrap/bend around corners.

 

[OldGuy]

Be very careful where you go to make rock molds. A number of years ago I found a thin coal seam exposed due to to a road cut. I parked on a frontage road, and was cleaning the coal getting ready to do my thing. A highway patrolman slowed down made a U-turn and wasn't all that enthuised with my activity even though I was 40 feet off the roadway (it was one of those areas where they cut and graded for a four lane divided roadway, but only paved two lanes). He left while I was packing up, so I managed to snag a boxful of decent pieces of coal that I made master molds while sitting in the comfort of my back deck.