Over the next few years, I hope to build a series of dioramas for the Sutro Tunnel museum in NV. Each will be in F scale, and feature different rolling stock of the Sutro Tunnel Railway, in a unique scene. All will be indoors, but in a building that’s not climate-controlled. Each diorama will be contained like a shadowbox, with a protective window, and be internally lit.
At the moment, I’m trying to nail down approaches for various features, such as terrain (which, in this tunnel, can be on walls and ceiling as well as floor). The basic shape of the environment will be made of EPS foam sheet, glued together, and roughed up. At least for now. For example:
Inboard of the EPS there will be a margin, approx 1/4" thick minimum, for the terrain surface material (shown darker). That will be applied after wooden features such as ties get installed.
I’m counting on the clay-filler to vary the terrain-surface and make it believable. But it’s gotta stick forever to the EPS foam. And not shrink & crack badly. BTW I’ll add texturing materials over this substrate.
But now comes materials cost, because we’re on a tight budget. I trust epoxy clay, since I made a hill of it for an outdoor mine several years back, with a surface about 3/8" thick, and it’s never cracked or degraded. But it costs about $9.5-$14.5 per pound.
The cheap alternative is air-dry clay, such as from Crayola, which is about $2.5 / lb, or DAS, at about $6.50 / lb. Or Activa at $3.7.
I ran across this video on air-dry clay adherence to different types of foam (using DAS), and it was very informative. Seems that roughing the foam up is critical for adhesion. Medium-density EPS seems to do ok.
But, I’ve read that the Crayola air-dry foam can shrink like 10% or more, so that doesn’t sound good. Not sure about the DAS or Activa clay.
Either way, I’m a bit concerned about the ceiling, and may glue & stab some dowels into the EPS above for the terrain material to grab onto.
I’m leaning toward the epoxy clay, but has anyone used the air-dry? If so, what brand, and does it shrink badly? I plan on doing a test between the two on the diorama shown, air-dry on the left, epoxy clay on the right. I’ll use Activa for the air-dry, since it says it has minimal shrinkage, and Smalltongue for epoxy, since I have some on hand.
We’ll see what happens.
Suggestions welcome,
Cliff
