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Thread: I was wondering if any one has used spray foam like tough stuff for scenery.

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    Icon6 I was wondering if any one has used spray foam like tough stuff for scenery.

    I am sitting in my chair looking at another rainy day in SE Mi. Seeing as I have free time until 4:40 I was wondering if this type of foam could be used with newspaper wads instead of plaster cloth.
    They make some that is highly expansive and moderately expansive. I have used it to seal any cracks or crevices around my house and it hardens pretty quick compared to plaster. If you carve your foam then this should be softer then plaster. The biggest question I have will it play well with things like foam risers and pink or blue foam for the base?

    If i can get motivated Iíll go to Home Depot and buy a can or two of the different types and just play around, if I can motivate myself to get off my (donkey) and do something important like going to Home Depot

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    You can certainly use it to build terrain, it's been done before. I don't know how it would work with wads of newspaper though. You don't get much control with it, especially as it expands, but it can be carved easily. It's great for filling in gaps between foam insulation layers and is a fantastic adhesive for foam as well.

    You might try newspaper wads as a base, covered with cardboard and tape to provide basic structure, then solidify the landform and fill any gaps with the expanding foam. Carve it to shape when finished and apply scenicking. Would be lightweight if you are doing a portable module.
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    I was thinking of the paper and cardboard strips. Maybe a light first coat and a thicker one after the first layer.
    I wonder if I used some precast rock faces stuck to it like Woodland Scenics suggests and sells molds as well as per older rock outcrops etc.
    since I am new to (relatively speaking) this hobby I really don’t want to invent the wheel again but I am a curious or nosey as my spouse describes me

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    Quote Originally Posted by Marksomebody View Post
    I wonder if I used some precast rock faces stuck to it like Woodland Scenics suggests and sells molds as well as per older rock outcrops etc.
    I would wait until the foam was setup, else your rocks could move out of position as the foam expanded. It should not be too difficult to attach them to the cured foam and you'll know where they'll wind up that way.

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    Hi Mark -

    I did a Google search for using "Great Stuff" expanding foam for model railroad scenery and got lots of hits, including some videos. Might give you some ideas.

    Here's the search:
    model railroad scenery "great stuff" foam

    - Jeff

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    I use GS. Usage has been described in past threads here on nscale.net, but if you have used it on your house then you are aware of it's characteristics. Here is a WIP landscape.
    IMG_7251.jpg
    The photo shows where the GS has been carved. The new foam on top is where I decided to redo the mountain top from what was originally there.

    I don't use wadded newspapers. I use cereal box cardboard, stapled to the underside of the raised roadbed (on risers) at the top and bottom of the slope. The cardboard provides a base for the GS, so you want the slope of the cardboard to go an inch or more below the final finished slope. The cardboard adds a lot of stiffness and structural integrity to the slope that would be absent if you use newspaper or masking tape; it's like the skin on a structural foam board. Once the foam hardens it also adds stiffness to your roadbed. Note the GS is not just stuck to the cardboard, but also to the edges of the plywood roadbed for maximum strength.

    I usually spritz with water to speed up the curing. Carving is quick and easy with a serrated steak knife.

    I used Durabond plaster in the photo for the carved rock work. I've also used Sculptamold which ends up super strong. Apply the plaster or Sculptamold to carved surfaces; nothing will stick to the as-cured shiny surface. I start by rubbing it into the carved surface to get good adhesion, then apply a thicker layer for the slope or for carving.

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    As others have pointed out, Great Stuff or other similar spray foams are suitable as a substrate, but you generally need some sort of finish layer on top of that for your presentable scenery (not just paint). I use Great Stuff topped with my own blend of ground goop, which is a water-mixed paper-mache variant that doesn't set up like plaster but rather just dries out. The Great Stuff becomes self-supporting after it cures, so it only needs enough support at the start so that it goes into roughly the right location. I've had success using hardware cloth from the hardware store (think of chicken wire but with a finer spacing, roughly 1/4") to pre-shape a mountain, and I've also used plain masking tape draped over some rough cardboard strips to make sort of a basket that I spray onto. Whatever you use, you need to make sure it is at least an inch or so lower than your target elevation, maybe more depending on how thick you will be applying the foam and the finish plaster/goop.

    The skin that forms on the cured blobs of foam is very slick and your plaster/goop won't adhere to it, you will be relying on the nooks and crannies to provide sufficient mechanical grip. It makes sense to take your serrated knife and carve away some of this skin, even if you don't really need to lower the terrain, just to expose the interior sponge bubbles. The finish layer will get good mechanical adhesion with the exposed interior sponge.

    I use ground goop that does not cure like other plasters, as mentioned; plasters that cure can be self-supporting in their own right, so it doesn't make as much sense to give them a comfy bed of foam. But my ground goop is "soft" in comparison and needs the support. This "softness" translates into being less brittle, less prone to chip. I've been very pleased with how well this system has held up on my N-Trak module, which is over a dozen years old now, exhibiting no cracks or bare chips.

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    Is it true that with these spray on expanding foam that you only get one to two time usage per can before the tube/opening seals itself up? So basically plan for a big area to spray?

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    I have had success with getting two spray sessions out of a can, provided you let the tube/nozzle seal itself over after the first spray. Then you can cut the clogged tube off, and replace it with a drinking straw of the right diameter, and go again.

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    Quote Originally Posted by kingmeow View Post
    Is it true that with these spray on expanding foam that you only get one to two time usage per can before the tube/opening seals itself up?
    Actually, I discovered WD40 will wash the still wet foam right off. Doesn't take much either and then you can just keep right on using it until the can runs dry. I imagine it will work with other oils.
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    The GS they sold last fall came with a plastic valve for the end of the nozzle that is supposed to stop the foam in the tube from curing. It's new this year; I was able to use the can a couple of days later.

    GS also has a shelf life; last year's can won't expand as much as this fall's batch.

    Acetone works for cleanup if it is uncured. Best to wear gloves, its Gorilla Glue with air.

    Pic of GS with Sculptamold rock work in my bridge album.

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    WD40 the duct tape for separating instead of mending.

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