Another use for sand and wood dust

This method was published in Model Railways Online Magazine: by myself several years ago as a method of building my viaduct: As Chris says, it is a very cost effective method but does have the disadvantage of being very time consuming. It took me 3 months to build the 1M long/20cm high viaduct in the above picture (5 foot radius curve). The really good thing about the method is that I personally believe that plaster treated with grey water colour is about the most realistic stone effect you will get. Here are some photos of my viaduct under contruction:
The method is particularly useful for large stone wall areas and doesn't suffer from 'joins' which you get with embossed plastic sheeting.
I wouldn't recommend adding anything to the plaster except perhaps, paint, as any impurity will cause weeknesses. I found that the Dremel was best used 2-3 days after the plaster had been applied - it was still slightly damp, but not fuly hardened and responded well to a mini counter-sink for carving. I did add wallpaper paste to my plaster to prevent cracking (was very successful): this is what Polyfiller is - at AU$10.00 per bag. Go to the builder's section of the DIY centre and buy 20KG of builder's plaster for AU$7.00 and some wallpaper paste for a few $ and you are way ahead! Don't go for the brand names and use basic builder's products!
Graham Plowman