Plaster Hardshell Terrain

By Ty’s Model Railroad - 12/27/2011 08:36:00 PM

Final layer of plaster being applied by hand to hard shell terrain

For my terrain structure, I opted to use the hard-shell method. This consists of cardboard strips, plaster infused paper towels, and a final layer of plaster. This seemed to be a popular, tried and tested method. The materials are very cheap and the end results are very effective.

Cardboard strips being installed to the sides of a track grade to form the base for hard shell terrain

Cardboard strips being installed to the sides of a track grades and benchwork to form the base for hard shell terrain

I first started by cutting several different length strips from a cardboard box, all between 1/2" and 1" wide. The strips were then bent to the desired curvature and fastened to the benchwork with either white glue and staples. I spaced each strip about 1" apart. For most of the strips, I didn’t require horizontal support strips except where the vertical strips were longer and tended to sag. Crumpled newsprint under the strips also helped with support in some areas. 

Cardboard strips and crumpled paper balls being applied to model railroad benchwork to form hard shell terrain

Cardboard strips being installed to the sides of a track grades and benchwork to form the base for hard shell terrain

I also incorporated some crock outcroppings that I had cast with plaster. For the more rugged looking terrain features, I used the same crumpled paper method that I used for my mountain tunnel. For future planned roads, I simply cut a desired sized piece of cardboard and attached it just as I did with the other strips, ensuring a smooth grade from the upper level to the lower ground level.

Paper towel strips soaked in plaster being applied on top of cardboard strips to form hard shell terrain

Paper towel strips soaked in plaster being applied on top of cardboard strips to form hard shell terrain

The next step was to cover the cardboard strips with plaster-impregnated paper towels. For this, I tore sheets of paper towel into strips at various widths. Preparing a good mixture of thin and wide strips cardboard strips makes it a lot easier to cover larger and smaller areas.

Paper towel strips soaked in plaster being applied on top of cardboard strips to form hard shell terrain

I mixed powder drywall compound into a large, shallow container with water. This took a little trial and error to get the right consistency; if too thin the paper towel strips will dry and peel and have no rigidity. If too thick, the paper towel will just rip under the weight. Good quality, brand name paper towel also helps immensely. I had to keep stirring the plaster mixture as I worked as the plaster tended to settle to the bottom of the container. Adding a bit of water to the mixture as I worked will also keep things flowing.

Paper towel strips soaked in plaster being applied on top of cardboard strips to form hard shell terrain

Paper towel strips soaked in plaster being applied on top of cardboard strips to form hard shell terrain

Once I had found the proper plaster mixture, I dipped in each strip of paper towel, wiping off the majority of excess plaster from the strips with my fingers. I then positions the paper towel strips horizontally across the cardboard strips, overlapping them for added strength. I didn’t worry too much if the paper towel strips sagged a bit between the cardboard support strips as this would be leveled off later with the final plaster layer. I used my fingers to smooth the strips as much as possible.

Final layer of plaster being applied by hand to hard shell terrain

After 24 hours the paper towel shell was dry and I was left with a rigid, somewhat brittle shell. I then applied a layer of plaster to the shell. This adds strength to the plaster shell and levels out any seams or sagging spots that may have formed. I used a gypsum based plaster but made the mistake of using a pre-mixed product. This is much more prone to cracking and shrinking compared to dry mix so, I had to go back and fill several cracks that had formed. I also cast a retaining wall right in front of the turn table using a cardboard mold that I made. The wall is cast with plaster of Paris and detailed with hand carved bricks.

Plaster retaining wall cast in place with plaster of Paris between two benchwork elevations

Once the first layer of plaster dried, I spread a second, final layer of plaster over the entire shell, thicker in some areas to eliminate low spots. I blended in all of the rock outcroppings and filled in any holes or cracks. I used a combination of my hands and small plastic spatulas to smooth and level the plaster layer and blend it with the existing bridge abutments and terrain. Ground foam and dirt will fill in any deficiencies in the plaster once it's added. I still have a few things to touch up but I can finally say that the plaster hard-shell is complete.

Final layer of plaster being applied by hand to hard shell terrain

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8 comments

  1. Enjoying your wonderful blog. I am just starting a new layout. (Had one many years ago before we moved house). My 9 year old grandson is helping me.

    One problem I have is that I am trying to keep the weight of the layout to a minimum as it will be stored close to the garage ceiling when not in use. Using a boat winch to raise and lower. Is their any other material I could use instead of plaster of paris?

    BTW the layout is 1800mm x 1200mm.

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    Replies
    1. Hello, that's great to hear that you are starting up a new layout with your grandson. I can imagine he is quite excited!

      I would say that the lightest weight option would be to use either a paper mache method using chicken wire or cardboard for support, or solid Styrofoam which you can then carve. A thin layer of plaster on either option shouldn't add much eight and should provide a solid base for your scenery. I think the benchwork itself will be the most concern for weight. Keep me updated on your progress or with any other questions you might have. Thanks.

      -Tyler

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  2. Hi there,
    Thanks for your quick reply.
    I had already started my layout, but on seeing your blog - which I accidentally stumbled on, and I'm glad I did - my plans went out the window!!! :) As I am sourcing my track from eBay, I can't replan it properly at the moment as I currently have a mixture of Hornby, Atlas, Peco and a couple of pieces of Tyco. I need some more straights before I can plan it using SCARM.

    I am impressed with your layout so - if you don't mind - I will base mine on it albeit slightly smaller as my base is a bit smaller than yours, I noticed on one of your entries that someone was asking about a copy of the elevations, or something similar. Would that be feasible if you could oblige with the same for me?

    Re using chicken wire for support, would plastic/artificial or whatever you want to call it, flyscreen be just as good.

    Thanks again for your reply.

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    Replies
    1. OOPS! I omitted to say that my wife and I were in Canada last August, and did the Rocky Mountaineer as well as the Canadian. I was going to incorporate part of the spiral tunnels on my layout, but I figured I don't have enough room. (:

      Thanks again.

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    2. No problem, I don't mind at all if you base your layout at all. As always, feel free to use, modify, or improve anything that I have done. I'm not sure if the bug screen will provide enough support for the terrain, where as chicken wire is much more rigid. If you used the fly screen, you would have to put a lot of material under it to support it. Keep me updated on your progress, I would love to see some pictures!

      -Tyler

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    3. Oh, and here is the ling to my layout showing the different elevations. Let me know if you need anything else. Thanks.

      http://3.bp.blogspot.com/-s9TULwKdIEM/VMbp21KC1xI/AAAAAAAACbQ/HVLOpHHCvEM/s1600/Elevations-%26-Track-Layout.jpg

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    4. Hi Tyler,
      Just an update on my plans. I have produced 2 layouts on SCARM, but still not sure which one to use yet. I haven't set my heights as yet, that will be done in the next few days. I have based (plagiarised) on your layout albeit a bit shorter than yours.

      I will email you with the layouts.

      Thanks again

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    5. That's awesome, I look forward to seeing them both.

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