True Ed but not a complete waste of time as it made me take five minutes to look at the link. The original site is gone but there was an article here on YMRC that contained most of the information, unfortunately no pictures as they are gone from photobucket, but still a good read ! 
   I've amended the original link to re direct to This old article

I don't hold out much hope of replacing the photos but I'll add it to the list  :roll:


 Cheers

Matt

White packing styrene sheets are usually not suitable for rocks, embankments or similar. Same goes for ceiling tiles. Usually too soft, and the cells are too big for sanding or cutting with a saw. HD closed cell foam sheets 0.5 to 2 inches thick as used for insulation in walls is much better. And is best cut and sculpted with a hot knife or hot wire. It also sands nicely with 320 grit paper. Make rock cracks or crevices with a pointy object or the hot knife (old dart heads are ideal). You can even carve bricks, stones or blocks using a dart head.

While it is tempting to use tenon saws, the bread knife or the Sunday roast carving knife, don't. They will be blunt beyond redemption after 5 minutes. Use disposable blades (Stanley or similar), even they will be blunt after a few cuts. Hot knives, or hot wires cut and sculpt it easily, and with a bit of practice the foam will look the job. Watch the dust generated while sanding, I run the shop vac while doing it, otherwise the whole house will be covered in tasteful pink or blue dust. Accompanied with the cry of "what have you been doing!".

Make sure the correct adhesive is used. There are special CA glues for styrene foam, as well as caulk type construction adhesive. Closed cell styrene foam will generally take solvent-based spray paint if the original finished surface is there, if not it will be eaten away. Plaster cloth stick well to a sanded surface.

Or you can just get some rock molds and make your own using plaster of Paris. Much heavier though.

Nigel

Hi Nigel     Thank you for your reply. After being advised on the dodgy content of YouTube videos, I watched one, bearing in mind that advice, of a Modeller “attacking” the foam with a flame from a small blow torch ( chef type)not for me though, for all I know he could have had the fire brigade.l department standing by. By my standards ( none)
a couple of sheets of O gauge stonework wall reinforced with something suitable would fit the bill, suitably shaped and weathered. If my plank or modules were to remain “ portable “ ? light is the key word. Best wishes Kevin 

Hi Kevin,

Yes I saw that one. Heating sytrene foam with a naked flame can get quite dangerous. Ijit comes to mind. Hence hot blades and wires. For your purposes some reinforced card with printed weathered bricks or stones glued to it is all that is required. I was actually thinking Lego bricks would do the job. Glue or screw the bases to the board either side of the tracks, make 4 sections of bricks glued together and weather them, drop in place as required, but O scale? Going up in the world?

Nigel

Hi Nigel.  Thank you again . There is a Members layout on YMRC in OO Gauge and he uses O gauge brick walls on his layout to good effect.   Best wishes Kevin 

I find expanded polystyrene quite satisfactory for rocks once you've covered them in plaster.

As for Knives for cutting poly, visit a pound shop, packs of half a dozen very sharp break off knives for ….

Hi the Q.  Thank you for your reply. I will “ Bank that info “ as I must sort out my Electrics first. And it should be straightforward? Which it is?   Best wishes Kevin