
Lionel used glue-soaked felt for some of their big tunnels in the prewar era, and the postwar #920 Scenic Display Set came with a big piece of felt, two tunnel portals, powdered glue, a bunch of other scenic supplies, and detailed instructions on how to build a tunnel similar to those made two decades earlier. I think this set was sold for one year only (1957), speaking to the complexity of building it.
The Elastolin tunnels made both before and after the war used paper mâché as covering. It's something I'm familiar with, and it gives a decent result, especially if you're looking for something that looks of-the-era.
American Flyer made their prewar tunnels out of paper mâché composed of ground up paper/wood fiber soaked with glue. They must have used a mold to form them, as there's no interior framework other than a metal hoop used to reinforce the "portal". Back in the early days of collecting this stuff, I'd occasionally see these tunnels in the antique stores, not realizing they were made by the company. It's a wonder that any of them have survived.
Anyway, I'll let this dry thoroughly before the next step - applying the paper mâché, a process only slightly less messy than applying the glitter































