rock - cliffs and cuttings

rock cutting behind the station

Every now and then, one sees a model railway that represents rocks by sticking stones or slate waste into plaster. Not surprisingly, it looks just what it is! Some modellers use flexible rock moulds that are available on the market. Some of the are very good but usually gaps are left between castings that never look to good. I always form and carve my rocks from plaster and have never been disappointed with the result.

If I am adding rocks to a shell topography the first job is to add Polyfilla to where rock cuttings are needed. This is shaped using a small steel rule, dental picks and a toothbrush (always use someone else's) when the plaster is in varying stages of hardening. We find it is often easier working with the baseboard on its side. Notice the rock drill marks.

Glenthorne Cutting (the rock drill marks can be clearly seen)

It is important to remember that plants will find a foothold in the most tenuous of circumstances except in very dry conditions. Even a tiny crack will support life after a little while.

For building the cliffs on our harbour module, I have used a modified version of this technique. The North Devon/Somerset cliff are very specific so I had to find the right way to do it.

punishment of foam with a 'Black and Decker Devon cliff maker'!

the cliff ready for coating

Once satisfied with the shape, the cliff is then coated with Polyfilla. This we mix to a consistency of double cream and brush on in the direction of the rock strata. We use a very short bristle brush for this ( a 1" throwaway cut down with scissors). When nearly dry, the Polyfilla is again brushed to knock off any nibs.

The surface treatment of the cliff. Some work is still needed on the tunnel portal.

After a wash with thinned brown emulsion. There is still much carving and detailing to be done. The tunnel entrance will be fitted with a concrete rock shelter.

The rock shelter was made in foam sandwich and then exterior varnished prior to coating with a thin layer of Polyfilla. Shuttering marks were made using a 6" engineers rule. One corner shows a re-enforcing bar that has frosted and broken out. This was a common problem with early concrete structures. The rock bolts (Grandt Line) can clearly be seen.

the rock shelter - notice the rock bolts

the completed cliff face

The rock faces of Cliffhanger under construction.



photo Mario Rapinett

This is a method developed by Mario Rapinett (aka Big 'M'). We have used the method with great success.


  • Old upholstery foam: This is easily obtainable from your local upholsterer. The reconstituted chip foam is not normally the one to use except for 'special effects'.

  • Plasterboard (drywall) premixed joint cement ( sometimes called Topping coat ). Mix with a bit of water to give a cream consistancy.

  • hot glue gun

Tear up the foam to suit. Strata can be made using a household saw. Bits can be torn out at will.

photo Mario Rapinett

Glue bits of foam together using hot glue gun. Paint with a couple of coats of diluted joint cement which fills the foam pores.

photo Mario Rapinett

When dry, paint under colour with matt plastic emulsion. Finish using weathering powders.

photo Mario Rapinett