Paul,
Jack Verducci has written quite a bit about this subject, as he's made a lot of rock formations outdoors. We have one of his articles to download here (free): http://www.trains.com/grw/default.aspx?c=a&id=13
You can purchase rubber rock molds or use something like crinkled up tin foil.
Rene Schweitzer
Classic Toy Trains/Garden Railways/Model Railroader
Here in Slower Lower Delaware, we have no hills, and we have no rocks. We end up having to buy rock, and it usually is not cheap. So my question is what methods have been used to make rocks for an outdoor railroad. Are there molds, and what materials are used.
Thanks
Paul
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