Well over the weekend I decided to do a test of the asphalt planed for the diorama road. The other guys on the RA forum concurred with my reasoning that the Warhound would make a mess of standard road asphalt it walked on. I figure large main avenues of an Imperial city may be reinforced to support the weight of such heavy vehicles as superheavy tanks, but a smaller street would have just standard pavement, which is relatively thin and weak.
So I wanted to model heavily damaged asphalt, damaged not only by the Warhound’s steps but also potholes and other general traffic which causes potholes. To achieve this I wanted to try out a technique I read about on a military modelling site some time last year. Unfortunately I don’t have a link, nor can I find any references to it now. The idea is to use florists’ foam underneath a standard asphalt recipe (dirt, plaster, glue and black paint) so that once the asphalt dries it can be deformed by applying pressure, creating very natural looking cracks and damage.
So we start off with a slice of florists’ foam:
Then mix up some asphalt. I used dirt (I was in a hurry so just grabbed it from the backyard but usually you would want to sieve any impurities out), plaster of paris, a little PVA, black acrylic paint and some water. You really need to make sure you don’t skimp on the paint: in the end it turned out far too light (although remember in real life asphalt fades as it ages, so unless you’re modelling pristine new pavement you don’t want it to be totally black).
Apply the asphalt mix to the foam. Note that the mix won’t actually stick to the foam so it can be a little tricky. To smooth it out I ended up placing a piece of cling film on top and then using a glass bottle as a rolling pin. The only disadvantage of doing this is that it can leave the top surface a bit too smooth, so you may need to rough it up again afterwards. I’ve read that you can use some sandpaper on the cured asphalt mix, but I’d be weary of sanding marks.
Note that you don’t want the asphalt to be too thick. In real life the actual asphalt layer is only about an inch thick (generally atop a bed of crushed rock) so try to get your model asphalt down to about 2mm thickness (which is still far too thick according to our scale, but for practicality will work well).
The weather here has been pretty wet so it took the asphalt about 48 hours to cure properly. I tried doing some impressions earlier and later and found that the most realistic results came from doing it later. It’s hard to tell but the Titan toe has been used to compress the asphalt is it sitting on and in person it gives a really authentic subsided/crushed effect. It would look even better with a thinner layer of asphalt (I applied it too thick). The pothole looks great though! You can see that once it dried the colour was nowhere near dark enough.
So the next step is to start roughing out the diorama! I did do some priming of the Warhound last weekend so I might even begin putting down some basecoats soon enough. Although I’ve got a pretty hectic couple of weeks ahead of me so it might be a little while before the next update…
As always, happy hobbying!