Celotex Rockfaces?

[TT-Pete]

I am going to need to produce quite a few sandstone rockfaces and outcrops for my layout, aiming for this overall look and feel:

I've been thinking about this for quite a while and have rejected the idea of using off the shelf pre-formed plaster rocks, or moulds to cast my own as firstly, who knew plaster could be so expensive? And secondly, I am going to need rather a lot of it and so would end up using the same shapes over and over.  

 

I was really impressed by the "knitterfelsen" (wrinkle rocks) system from Noch where flat sheets are folded to give a random 3d effect,

but at £10 for each 25x45cm sheet, you might as well be using papier-mache made from banknotes!

 

I do however have a pile of Celotex sheets and off-cuts left over from our housebuild squirreled away at the back of the garage and I am assuming it can be worked very much in the same way as the stuff by the chap in this video:

 

I've seen in a few posts here that people have worked with Celotex on their layouts so I am going to give it a go and just wanted to ask for any tips and tricks anyone might have for shaping/sticking/painting the stuff, and what definitely needs to be avoided? E.g do particular glue/paint/solvents melt it?

 

(The other half is going to just love the mess once I actually get started with it... )

 

[crompton 33]

I've used Celotex for rail cuttings on my layout.  Found the best glue to use was No Nails . It's been down for 8 years .

[teaky]

I agree.  An inexpensive grab adhesive works fine on PIR insulation.  Just make sure it is a solvent free one.  Screwfix own brand No Nonsense has been my first choice for years now.  Their flexible decorators filler will also stick to PIR insulation without any problems, should you come across a need for something like that.

 

I'm impressed with that second video and I'm looking forward to your experiments.

[brack]

I found that with a thick ish sheet (50 or 75mm) stabbing downwards in a jaggy line into the thin edge with a serrated knife then splitting into two halves produced a decent start for cliffs, with loose bits then knocked off, strata added and so on giving a good result.

[TT-Pete]

On 24/11/2019 at 16:04, teaky said:

I'm impressed with that second video and I'm looking forward to your experiments.

 

Hi Rob,

 

I've had a first stab. Noticing an offcut on the floor had a rough-sawn edge I picked it up, selectively roughened it up even further with a small flat-bladed screwdriver and splodged a bit of paint over it:

 

 

Not too bad I think. It needs a bit more experimentation with the paints and shading, but I may be onto something here... :^)

 

 

[teaky]

You're fooling no one.  Trying to pass a piece of rock off as some painted insulation.  Pah!

[teaky]

You are definitely "onto something", Pete.  That looks great.

 

Perhaps some photos of the real thing might guide which paint colours to select?  It really is good already though just with the splodged paint.

[Alister_G]

I used 25mm PIR in layers, stuck together with solvent free adhesive:

 

 

I put a skim of Wickes cheap ready-mix flexible filler on it, and shaped it a bit, then I gave it a blast with a couple of rattle-cans - grey and tan colours.

 

This is seven layers of 25mm.

 

 

However this isn't finished yet, it needs detail painting.

 

Previously I did this with a similar technique:

 

 

Al.

[peak experience]

geologist's hat on. look at the real thing and study it closely. i see all too often the correct attention to detail regarding buildings/infrastructure etc whilst rock exposures sometimes seem to be conjured up from the imagination. the photos you've chosen as your prototype show thickly bedded, well jointed sandstones, that are horizontal. the last point is a bonus for you as you can just stack in layers as Alistair G has done above and not have to worry about 'dipping' beds. good luck.