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I think that good rock molds look more realistic than what I could create by carving cast plaster or from other types of scenery base such as Mold-a-Scene, which is what what I sometimes use. Some rock molds are made by casting actual rock shapes into molds and look more natural to me than anything I could carve from plaster. As far as real rock, it's heavy, and I prefer to keep things lightweight on the layout .


Last edited by MELGAR

Another option is to carve Styrofoam with a hot wire cutter. This works well for smaller rock cuts. Takes some time if the space to cover is large. Results in a light rock face, which in my case, is easily removable to access the track and hidden wiring.  I have rock moulds, but have never used them. I am avoiding the mess or working with plaster. Nothing wrong with plaster, I am just avoiding it for now.

Rock molds are in most cases easy to use, faster than carving and like GRJ mentioned, you can use the same mold over and over and just by turning it in different ways you would never know that it was the same mold and it was just blended into each other or into other rock molds.  They make for some really beautiful rocks too.,  Try them, you might really like them.

BTW Scott - I agree with those advocating rock molds and use them extensively myself.

Here's an option - the "rocks" shown below directly above the GG-1 were created with simple aluminum foil. First, you "steal" the foil from your wife, crumple it up, and then stretch it back to a reasonable shape, spay it with a wetting agent (plain water with a drop of dishwashing liquid), cover it with hyrocal from Woodland Scenics, apply it to the desired area, and then remover the foil before the hyrocal completely sets up.



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For me it was molds from Bragdon because there are no rocks in The Netherlands but the molds from him are the best there is because you should not forget to look carefully at scaling down. Making rocks was not an option too much work for me and his molds were perfect of course with a lot of chopping I make also some. Real rocks are way too big for my job and neither fit nor realistic. I do this because I had a specific goal and can only be done with his molds and to scale. But everyone (railroaders) has their own way which is nice because it always remains a hobby. I have seen a lot layouts with beautiful rocks on O gauge Railroading Forum. The color is also very important I used 3 colors some 4 to make this.

There are some pictures some of them never was on this forum.


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@trainbob posted:

I think this thread should be renamed to some great images of rock formations in model railroading and a note to ed3945 please make all of your photos able to be enlarged thanks guys for some great photos

@trainbob   Click the photos at the bottom in the attachments section.  I think they will enlarge for you then.  Also use the white arrows in the middle left or right to cycle through the whole group.  Hope this works.

This is actually a pretty interesting topic.

Although I think @ED3945's rockwork is some of the very best I have ever seen, I disagree that scale matters. Rock surfaces are fractal, meaning they are similar at all scales. There is really no way to tell the scale of a rock photograph without some kind of external reference. This has been widely discussed in the geology literature.

BUT, what DOES matter is intended viewing distance. If you are modeling a close-up view of  a rock cut, then getting the details exactly right is important, and molds are one good way to do that. However, if you are modeling an escarpment in an attempt to simulate a distant mountain view (which is a kind of forced perspective), then excessive detail is not only a waste of effort, but it is actually harmful. Modeling details that the eye could not resolve in a real scene can break the illusion of distance.

The following scene uses a combination of real rocks slabs (chosen for their lack of fracture details) and rather crude plaster work:

The level of detail is very low, but this contributes to the illusion of depth.


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Last edited by Avanti
@mwb posted:

It's not necessary; in fact, very little is actually necessary.  Well.....dodging a wrench might be.

But they do tend to make far better rock outcrops, and mountain scenery than most people can make carving whatever materials you care to invoke.

"If you can dodge a wrench you can dodge a ball!"...Patches O'Houlihan.

Thanks, If there is a interest I take more pictures of my rocks and how I did it. I have pictures of the beginning. I have what I say to myself a horseshoe track or layout like  a U. On the other side of my layout I have rocks what I started in the beginning with old molds the one you saw is from Bragdon molds and a lot of cutting rocks myself and I try to make bigger pictures.

Last edited by ED3945

A look back almost 20 years, the rocks, from Woodlands Scenic rock molds, were one of the first layout projects, done with hydro-cal.   My wife and I had purchased one of the Kalmbach (How to), books on scenery.  I did a lot of sub-structure, with wood, today, sub-structure is done with foam/foam board.  There were, from Woodlands Scenic, three, maybe four, different rock molds. I also had a tunnel mold, only available in HO.  Scenic Express a forum sponsor, I think ??, has the rock molds.   Once I had a supply of pieces, assembly was relatively simple, with construction adhesive.  All pieces/parts were used. Patching holes, in the detail, was done with Hydrocal, or Plaster of Paris.

This pond/creek area was a drop-out section, of the layout. The majority of the work, on this section, was done in the shop.  The piece was installed from below the layout.  Plaster cloth, wet and apply, was also used to blend different rock parts.   Ground cover, material and application another discussion.


Hole to the left eventually became the creek/pond.



Additional comment, 1/14/21,  IMO  5% to 10% of all layouts get to this point. IMO  Enjoy the hobby.  


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Last edited by Mike CT

If you don't have a lot of ground to cover, you can always use just the commercially available Polyurethane Foam masters themselves.  They can be cut and shaped to fit irregular spaces, and then colored and landscaped to get the look you want

These are from Reznor Enterprises.  I think they are no longer available, but you can get similar products from Atherton Scenics Plus on eBay






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Last edited by John Sethian
@dan 77 posted:

I plan to use the half dozen Bragdon rock molds I already purchased.  My carving skills are not great,  so rock molds are my answer for realistic rocks.   BTW lots of great looking rock features.

Your dentist would have old tools that are discarded regularly.  IMO These tools work great for carving/picking/shaping hydrocal rocks, or foam board.   Caution:  Some paints don't work well with foam board.    IMO. Mike CT.

Last edited by Mike CT

I used 5-6 molds to re-create the Maryland Heights cliff above Harpers Ferry WVA on my old layout.   I had lots of pictures of actual site to reference and I think it came out pretty good.   I started with a base mountain of chunks of leftover packaging styrofoam that I stuck together with Greatstuff foam insulation.  Next I draped the surface with paper towels dipped in plaster.  Next I plastered on the rock molds and filled in gaps using the Battista method (check out his first Black Diamond Railway video).  The plaster rock also takes coloring very well and I was able to match the rock color with the backdrops I printed from my photos.  I also used masonite to create a thin relief rock wall made up of broken ceiling tiles, rock molds, and glued on greenery.   Was well worth the effort.

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