6. Adding Depth
Although a fine runway can do its job, a more complex and detailed diorama can make a difference between a nice scale model and a real masterpiece. Personally, some grassy spots on a barren field, or even an entire grass strip both represent one of the most beautiful detail you can add to your airfield. Let’s have a look at how to create these features.
Preparing the Terrain
Depending on the roughness of the terrain you desire to reproduce, it might be appropriate to modify the flat and smooth surface of the styrofoam sheet. To do so, you can undertake various paths.
The first option consists in adding further styrofoam layers, properly cut and eventually carved to suite your needs. You can easily glue these additional parts with white glue and, if needed, keeping them more strongly in position with some toothpicks. As an alternative, you can put some putty or modeling clay on your diorama and mould it until it fits the result you want to achieve. However, this last tecnique is more suitable for small areas, since it usually requires a considerable amount of putty.
Dirt, Mud and Sand
Otherwise, you can opt for a more “natural” option that can result in very realistic scenarios. This consists in blending water, white glue and fine sand or dirt to obtain a mixture that can be applied where needed. This is perfect for large surfaces as well and, personally, is almost incomparable in terms of realism.

The mixture is roughly composed of 60% dirt (or sand), 35% of white glue and 5% of water. Water, however, is not indispensible and, should you notice that your mixture is too fluid, just add more dirt until a mud-like substance is obtained.
I would like to point out that the fineness of the dirt (or sand) you are using is crucial to obtain a realistic effect. The smaller the scale of your diorama, the finer your soil has to be in order to properly resemble reality. This mixture can be easily painted once dry, allowing you to use it to reproduce concrete as well. In this case, using sand instead of dirt results in a better effect.

For my model, I decided to create a small “concrete” slope between the runway and the surrounding field. This has been created using a fine river sand with the previously described method. Here is the mixture just applied (not dry yet).
A Colorful Soil
Prior to any application of “grass” and “plants”, it is important to paint the surface intended for this purpose. This is fundamental both to give a less regular aspect to the final result and to provide a first simulation of the grass layer that will be subsequently applied. To this extent, any issue already arose concerning the paint choice is still valid.
As shown in the photo above, an extremely irregular and uneven pattern is perfect for a rough and partially scorched field. Quite the opposite, a flatter and uniform painting can better simulate an airfield which runway surface is a grassy field itself.

To create this effect I first applied a brownish base, followed by an uneven deep green applied randomly, but more densely far from the runway. Finally, I added a grey-green paint in a spotty pattern.
If you have planned to frame your diorama, this, in my opinion, is the best moment to do so: just prior to apply the grass (or other types of greenery). I indeed think that delicate details such as grass, trees or bushes should be applied as late as possible, to prevent any further process from damaging your model.
For my airfield, I built a thin balsa frame, upon which I glued the model base with a styropor-kleber glue.
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