Expanded Foam or Newspaper?

[Connor]

Just about done laying my roadbed on my layout.. I need to lay some plaster cloth over some inclines before I can finish, which means I need to build up to my inclines. I'm tempted to use Expanding insulation foam that comes in a can, and spray it along the edge of the inclines to produce a "rocky" type surface, then cover the incline and the foam with plaster cloth. Has anyone done this? How does this work compared to newspaper? Also, I want to do 1 layer over plaster cloth over the incline, but overlap layers on the hillside.. Any recommendations?

Thanks, Connor

 

[Ralph]

Hi Connor,

My only experience with expanded spray foam is in home repair and I find it difficult to control. It can be carved once its dry though so I guess that's not a big problem. As I recall, Malcom Furlow used this material to shpe southwestern mountains on a layout with great success.

I use newspaper because its cheap, quick and easy to control.

Ralph

 

[who_dat73]

spraying foam

I have tryed the spray foam hill idea using it to build a hill all by itself and the real problem I ran into was if you are doing a big hill it has a tendancy to settle to the bottem and has a hard time holding to any height if it is a small mound you are making it might work?!
Also if you use it to any depth not sure how deep it will dry on the outside and still be soft any mushy on the inside.
Not sure if this will help but what I decided to go with was foamboard that I cut from my layout to build the sub structure then used plaster paper towels to make the final face.

 

[Matthyro]

My experience with that expanding foam hasn't been great as it usually grows more than I want. My preference is to use strips of corrugated carboard glued together in a mesh then coat with paper toweling soaked with plaster. Once cured I put a layer of floor levelling plaster over it and it can be sculptered to give good results.

 

[ezdays]

Not sure if you can do this, but I just glued cuttoff chunks of extruded (blue) foam the the sides of my inclines to build them up, then covered them with plaster cloth (really just paper towels soaked in plaster) and I layered that with joint compound to get the texture and rocky look I wanted.

 

[spitfire]

Cardboard, eh Robin? Now why doesn't this surprise me?

Connor, I'd stay away from the expanding foam, for the reasons already stated. It really does get out of hand quickly, and never stops expanding when you expect it to. You'll end up doing a lot of carving in place. Much easier, IMO to use extruded foam and do the carving on your work table or on the floor where you can get at it, then put it in position.

Val

 

[CBCNSfan]

Staying away from expanded foam is the thing to do. If I recall they seopped using it as flotation for boats something about gas and deterioration. All I seem to recall is it's bad stuff in enclosed areas. It's been a long time, sorry I've forgotten the whole story.
For my self, like previous posters I carve both the beaded and the extruded styrofoam to build up my hills and slopes. ( caution if using the beaded foam) use a very sharp knife to shape it nice clean cuts or you'll have little beads all over the place. The extruded foam you can shape it with various tools. In most cases when building a hill I just cut out the base, glue it to the bench work, cut another piece and glue it to the piece previously laid. You can use tooth picks bamboo skewers, whatever to keep the pieces aligned while the glue dries. Lay your plaster cloths, towels, over the structure and you have your hill.
The lumps or bumps on the ridge are just scrap pieces of styrofoam shaped a bit and plaster cloth over them.
Cheers Willis